ArticlePDF Available

Phenology of Sesame

Authors:
  • Sesame Research, LLC
144
Reprinted from: Issues in new crops and new uses. 2007. J. Janick
and A. Whipkey (eds.). ASHS Press, Alexandria, VA.
Phenology of Sesame*
D. Ray Langham
This paper describes the development of the sesame (Sesamum indicum L., Pedaliaceae) crop from seed
to harvest in terms of phases and stages. This description is based on experience over the last 40 years with
over 38,000 lines of sesame grown in 88 nurseries and over a quarter million hectares of commercial elds in 9
states in the US and 10 foreign countries. The lines include 2,925 introductions from 67 countries and crosses
between those lines. The observations have been made under conditions varying from irrigated to semi-irrigated
to rainfed; from rain in all phases to drought; from low to high fertility; from early to late plantings; from 17
to 100 cm row spacing; from sandy to very heavy clay soils; under all levels of weed infestation; from laser
leveled elds to sloping hills; from sea level to 1,000 meters elevation; in moderate to very high temperatures
(52°C); after very high winds (150 km/hr), dust storms, hurricanes, lightning strikes, light to heavy hail, frosts,
hard freezes, and snow.
Sesame is a survivor crop. For 5,000 years it has been planted by subsistence farmers in areas that will
not support the growth of other crops or under very difcult conditions with drought and/or high heat. In
some countries it is grown after the monsoon on residual moisture with no rains during its production cycle.
In some countries it is grown in the monsoon season and subject to daily rains during parts of its cycle. In
several countries it is the last crop that can be grown at the edge of deserts, where no crops grow. Very little
sesame is grown under high input conditions, although yields improve dramatically as inputs increase. Most
current sesame cultivars have been farmer selected or bred to retain the survivor qualities. In the US sesame
has been grown in Arizona under high inputs and in Texas/Oklahoma under low inputs with all levels of inputs
in between. While there may be exceptions to the following description, the phenology of any crop must start
somewhere, and this is the start for sesame.
Sesame germplasm has tremendous variability. The author has identied 412 different characters with wide
differences in some of these characters in the world collection. Different genotypes can develop very differently
under the same conditions, and the same genotype can develop very differently under different conditions. In
general, this description will be centered on the US improved cultivars. Each stage will be described in the
following sections: denition, time from planting of the stage, length of time within the stage, description, and
factors that shorten and/or lengthen the stage. Table 1 summarizes the phases and stages.
The key factors affecting the length of the various stages are as follows:
More moisture will shorten germination and seedling stages but will lengthen rest of the stages.
Higher fertility will shorten seedling stage but will lengthen the rest of the stages. (Effect on germina-
tion stage is unknown.)
Increased degree days over normal will shorten the vegetative and reproductive phases.
Cool night temperatures will lengthen the ripening phase and full maturity stage.
Low humidity, wind, and/or heat will shorten all of the drying stages.
Frost may and hard freeze will terminate the plants at any stage. In a freeze even though plants will be
brown in 3–5 days, they will not be dry for 7–10 days.
This paper describes 11 stages which exceeds the number in most other crops. The phenology analysis is
intended for 3 uses: for researchers to understand the growth of sesame, for farmers to get visual cues for tim-
ing of farming operations, and for plant protection personnel to understand the vulnerable periods of the crop.
This paper focuses on the researchers but includes the stages of interest to the farmer. For example, the pre-
reproductive appearance of buds is a visual cue for adding fertilizer, setting up the rst irrigation, and warning
that soon the plants will be too tall to cultivate. Few phenologies include a germination stage, but sesame is a
vegetable size seed planted with eld crop equipment and conditions. Understanding the germination stage can
lead to better strategies to attain a good stand.
*Randy Landgren provided a sounding board for the original delineation of the stages and provided some of the names.
Amram Ashri (Israel), Malcolm Bennett and Loretta Seran (Australia),Wasana Wongyai (Thailand), Churl Kang (Korea),
and Agustin Calderoni (Argentina) provided helpful comments and editorial work.
145
Edible Oilseeds, Grains, and Grain Legumes
There is a tremendous amount of variability in the vegetative, reproductive, ripening, and drying phases
of sesame. Sesame is an indeterminate species, and thus there is an overlap between the reproductive, ripen-
ing, and drying phases. The seed in the rst capsules to form may be mature while the upper part of the plant
is still owering, and there may be dry capsules before the top capsules have matured. The only other known
attempt at a sesame phenology was included in a Masters thesis, which divided the phenology into three phases:
the establishment phase (0–38 days DAP), the growth phase (38–80 DAP), and the storage phase (56–98 DAP)
(Triangtrong 1984). That phenology reects what is actually happening within the plant, while the phenology
in the present paper reects what can be seen in the eld. Table 2 shows the range and mean number of days
for each phase for nurseries in Uvalde, Texas, from 2000–2004 using data from 20,281 plots.
Table 3 shows the ranges for lines with commercial potential in the US. The lines in Table 3 have narrower
ranges in most phases, and the means are lower than those in Table 2. To date, very early lines do not provide
adequate potential yield, and very late lines have a production cycle that extends into a bad harvest window,
which can reduce actual yields substantially and degrade the quality of the seed. In Australia these ranges would
be vegetative 28–37 days, reproductive 35, ripening 20, and drying 40 (M. Bennett, pers. commun.). Often the
cycles are shorter in the tropics.
FACTORS THAT AFFECT PHASES AND STAGES
Populations
In the US, all commercial sesame is planted mechanically and not thinned. The author does not thin the
nurseries. The observations in this paper are based on unthinned stands ranging from very high (246 plants/m2)
Table 1. Phases and stages of sesame.
Stage/Phase Abbrev End point of stage DAPzNo. weeks
Vege t a t i ve VG
Germination GR Emergence 0–5 1–
Seedling SD 3rd pair true leaf length = 2nd 6–25 3–
Juvenile JV First buds 26–37 2–
Pre–reproductive PP 50% open owers 38– 44 1–
Reproductive RP
Early bloom EB 5 node pairs of capsules 45–52 1
Mid bloom MB Branches/minor plants stop owering 53–81 4
Late bloom LB 90% of plants with no open owers 82–90 1+
Ripening RI Physiological maturity (PM) 91–10 6 2+
Drying DR
Full maturity FM All seed mature 107–112 1–
Initial drydown ID 1st dry capsules 113 –126 2
Late drydown LD Full drydown 127–146 3
zDAP = days after planting. These numbers are based on S26 in 2004 Uvalde, Texas, under irrigation.
Table 2. Range and mean of number of days in phases for all Sesaco germplasm.
Days from planting Phase length (days)
Phase Range Mean Range Mean
Vege t a t i ve 29–59 42 29–59 42
Reproductive 5 6 –116 89 16 –7 0 47
Ripening 77–140 108 (14)z–54 11
Drying 102–181 150 11– 57 38
zIn some lines, there are dry capsules above green leaves while the upper part of
the plant is still owering creating a negative range.
146
Issues in New Crops and New Uses
to very low populations (1 plant/m2—in 1989 there was a single plant with over 2,200 capsules that produced
428 grams of seed). In the US, commercial elds are planted with planters ranging from row planters to drills.
Farmers have planted from 2 to 9 kg of seed per ha (570,000 to 2,540,000 seeds per ha). Farmers who do a lot
of tillage work to prepare a good seed bed, have relatively uniform soils, plant small elds, drive slowly, and
continually check/modify the placement of the seed, can get a good stand with low planting rates. These farm-
ers plant about 2 to 3 kg/ha. However, many farmers are reducing tractor passes across the eld, do not have
uniform soils, plant large elds, drive faster, and do not have time to continually check/modify the placement
of the seed. These farmers plant about 3 to 6 kg/ha. Drills are very imprecise (even modern drills with good
depth control), and those planters end up planting between 6 to 9 kg/ha. In addition to the land preparation
and planting practices, the germinating seedlings must face environmental factors such as rain that will create
crusts before emergence, a sudden cold front that will reduce the growth rate before emergence, winds that will
blow sand and damage or cover them, insects at the seedling stage, etc. Additional seed is a form of insurance
for a good stand, because there is no agronomic practice than can improve a poor stand other than replant. The
author has been planting 4+ ha nurseries in mid-May on the same farm in Uvalde since 1988 with the same
planter and the same planting rate (about 2 kg/ha). In that time, the populations have averaged from 12.5 to 30.8
plants per linear meter. The environment from the emergence through the juvenile stage is more important for
nal plant number than the seeding rate.
The population density affects the phenotype and the length of time of the phases and stages. As the plants
compete for light, high populations grow taller faster than low populations. However, unless there is consider-
able moisture and fertility, the nal height is usually lower in high populations. Given the same moisture and
fertility, high populations will use up the resources sooner and will go through the whole development faster
from the mid bloom to the late drydown stage. High populations will lose lower leaves faster since the light
will not penetrate the canopy. Since often populations across a eld are not uniform, there will be some areas
ready to combine sooner than others. In moderate to high populations, there will be dominant plants and minor
plants. The dominant plants generally emerged faster and since early growth is a geometric progression, they end
up with larger cotyledons leading to larger leaves and deeper roots. These dominant plants will begin shading
the other plants which will end up shorter with lower production. Compared to the dominant plants, the minor
plants will start owering later, will stop owering sooner, and will dry down sooner. Most of the data in this
paper is based on the dominant plants.
Some of the observations in this paper will not be seen in research nurseries throughout the world. In most
nurseries the plots are planted at specic distances and then thinned to the desired population. The plants are
not normally viewed at either high or low populations. In addition, the plants are grown with optimal moisture
(irrigations) and fertility. The author plants nurseries under farmer conditions in each area. If it is in a maize
area row spacing is 76 cm, in a peanut area 91 cm, in a cotton area 102 cm, etc. The nurseries are either fully
irrigated, semi-irrigated, or rainfed, and the fertility matches local farmer practices. Although it has been shown
that earlier plantings (once the soil temperatures reach 21°C) have higher yield, if the practice is to plant the
cotton rst followed by the sesame, the nursery is planted later.
In numerous yield analyses, the author has found little difference in the yields of populations between
10–26 plants/m2 with lines that adjust to the population, i.e., produce more branches in low populations. When
the stands are uniform, even lower populations plants can provide equal yields, and when there is adequate
moisture and fertility, much higher populations can still yield well. In Texas, Kinman and Martin (1954) found
little difference in yield between 2.5–49 plants/m2 because of high stand tolerance. In Australia, Bennett (1998)
Table 3. Range and mean of number of days in phases for commercially suitable
lines in the US.
Days from planting Phase length (days)
Phase Range Mean Range Mean
Vege t a t i ve 33–53 40 33–53 40
Reproductive 5 6 –114 81 27–52 38
Ripening 86–121 103 9–34 21
Drying 110 – 163 144 11– 57 43
147
Edible Oilseeds, Grains, and Grain Legumes
strives for 30–35 plants/m2 and Sapin et al. (2000) recommend 20–40 plants/m2. In Venezuela, Avila (1999)
found little difference between 30–35 plants/m2.
Moisture and Fertility
Throughout this paper there will be references to irrigated and rainfed, which are relative terms. Rainfed
elds near Oklahoma City have more available moisture than irrigated elds in West Texas where some farmers
irrigate but rarely with more than 25–50 mm of water. In the main sesame growing areas in the US, the aver-
age rainfall ranges from 480 to 940 mm and little of the rain (0 to 125 mm) is in the 70 days that are critical to
sesame in the reproductive and ripening phases. Rain that falls on a full moisture prole does not help; rain
that falls in the rst 30 days often will set back the plants more than it will help; rain after the seed is lled does
not help. In these areas summer rains are often in the form of strong thunderstorms that can have 25 mm of
rain in one part of the farm and zero rain 500 meters away. These same storm cells can drop 50 mm per hour
and much of the moisture can run off the eld instead of penetrating the soil. It is not unusual for storms to
rain 200–400 mm in one spot in 24 hours. The number of days in each phase of the phenology depends on the
amount of moisture available to the crop.
Sesame is drought tolerant, but as with every crop will do better with more moisture. There have been
many cases where sesame has done well in elds with low or no fertility, but in coming back to the same eld
the following year will not do as well. In analyzing the cropping history of that eld it was found the previous
crops were shallow rooted and it is hypothesized that the sesame roots went down and found nutrients that had
leached lower down into the soil.
There are two types of sesame: those used in dry areas or seasons (US, Venezuela, etc.) and those used
in high moisture or seasons (China, Korea, etc.). Many countries such as Thailand and India have sesame for
each area or season. Generally, wet sesame does not do well in dry areas but dry sesame may do well in wet
areas. The dry lines generally have a strong root that will penetrate deep into the soil to stay in the moisture.
The wet lines generally root shallower. There are intermediate lines that are productive in wet or dry but will
not do well in the extremes.
Within a line, there are two basic architectures with many gradations in between: high input and low input
architectures. The high input architecture occurs when there are good moisture and fertility during the vegeta-
tive and reproductive phases. The leaves are larger and the internodes longer resulting in a higher height to the
rst capsule, more capsule node pairs, and taller plants. The low input architecture occurs when there are low
moisture and/or fertility. The leaves are smaller, the internodes shorter, lower height of the rst capsule, fewer
capsule node pairs, shorter plants, shorter capsules, fewer seeds per capsule, lower hundred seed weight, and
lower seed weight per capsule.
If the plants start in high input mode and do not get the appropriate moisture in a timely fashion, the plants
will drop the lower leaves and newer leaves will be smaller with shorter internodes, in essence converting to
a low input architecture. During this conversion the lower leaves will drop until enough leaf surface has been
shed to equalize the evaporation to the available moisture. In some cases applying an irrigation too late after
the conversion can actually damage the crop by placing too much stress on the plants. Although a drought can
reduce yield considerably, in the US, sesame will survive a drought and make viable seed. If a crop begins in or
converts to low input architecture, it will not change to a high input architecture no matter how much moisture
and fertility becomes available. However, the plants will continue putting on owers and capsules despite the
small leaves at the top of the plant. The nal height of the plant is inuenced more by the vegetative phase than
the reproductive phase. Some high input crops look like they will be very high yielding because the plants are
so luxurious, but the plants may not yield as well if the high inputs are used in the vegetative stage, and there
is not enough moisture and nutrients at the end to make good seed ll.
Within lines planted in the same conditions there are two opposite genotypic architectures and all grada-
tions in between. In high input elds the high input genotypes will generally do better, and in low input elds
the low input genotypes will generally do better. However, across all elds, the intermediate genotypes will
produce higher mean yields.
The interrelationship between moisture and fertility is very evident. If there is adequate moisture and
low fertility or if there is little moisture and adequate fertility, the yields will not be good. However, in the
148
Issues in New Crops and New Uses
intermediate range it is not known whether moisture or fertility is more important.
Phenotypes
There have been several systems for classifying sesame. Hildebrandt (1932) divided sesame into capsule
types: bicarpellate and quadricarpellate. Kobayashi (1981) classied sesame by capsules per leaf axil, phyl-
lotaxis (the arrangement of the leaves on the stem), presence of nectaries, and number of carpels in the capsules.
Kang (1985) described sesame in terms of branching style, number of capsules per leaf axil, and number of
carpels. The author describes sesame phenotypes in terms of branching style, number of capsules per leaf axil,
and maturity class. Branching is the rst character with the following values: uniculm (1), few (4), or many (7).
Capsules per leaf axil is the second character with the following values: single (1) or triple (3). Maturity class is
the third character and is in terms of days from planting until physiological maturity. The values are very early
(V = fewer than 85 days), early (E = 85 to 94 days), medium (M = 95 to 104 days), late (L = 105 to 114 days) and
very late (T = more than 114 days). Table 4 shows the symbols for the various phenotype combinations possible.
In parts of this paper the phenotype will be referred to by just the rst two characters and preceded by “zx”.
Table 5 shows the distribution of released Sesaco cultivars. A large range of phenotypes had been developed
because different environments (frost-free days, temperatures, rainfall patterns, farmer equipment, and farmer
practices) favor different phenotypes. To date, no lines have been found that would fall into the 71E, 71V, 73E,
and 73V phenotypes. It is difcult for an early line to have many branches since owering is delayed in order
to have enough nodes below the capsules to have many branches. It should be possible to have an 11V line, but
it probably is not seen because of very low potential yield.
Commercial sesame cultivars worldwide have varied phenotypes. The early, medium, and late cycles are
determined by the environment. Late cultivars cannot be used in Korea because of a short growing season.
On the other hand in the tropics with mostly late cultivars, certain crop rotations favor early ones. Most of
the farmer-selected cultivars have branches with a single capsule since over time these types have survived a
multitude of poor conditions and/or weather disasters. In most irrigated or heavy rainfall areas triple capsules
are preferred with the Chinese choosing uniculm and the Koreans few branches.
Branching
Branching generally takes place in nodes on the bottom of the plant below the capsule zone. The amount
of branching is scored as “few” and “many” based on general behavior of the lines in different populations and
row spacing, and by observing the ratio of the number of nodes to the rst capsule to the total number of nodes
on the main stem. In low populations, “few branch” lines will have 2–4 branches, and “many branch” lines
have 6 or more. “Many branch” lines have more nodes below the rst capsule, and will have fewer nodes on
the main stem. Having dened the difference between few and many, the denition is difcult to apply because
Table 5. Phenotypic distribution of Sesaco cultivars and germplasm (GP).
Maturity Uniculm Few branches Many branches
Single capsule/leaf axil
Very late GP GP S12
Late S11 S22 GP S04 S05 S16
Medium GP S01 S08 S09 S24 S27 S20 S26 S28
Early GP S07 S25 S29
Very early GP
Triple capsule/leaf axil
Very late S06 GP GP
Late S15 S50 S51 GP GP
Medium S02 S10 S17 S19 S21 S14 GP
Early S52 S03 S23
Very early GP GP
Table 4. Sesaco phenotype
combinations.
11T 41T 71T
11L 41L 71L
11M 41M 71M
11E 41E 71E
11V 41V 71V
13T 43T 73T
13L 43L 73L
13M 43M 73M
13E 43E 73E
13V 43V 73V
149
Edible Oilseeds, Grains, and Grain Legumes
the amount of branching varies with different growing conditions. In wide row spacing with intense light a
“few branch” line will have 6 or more branches, and under low fertility and moisture, a “many branch” line will
have 4 branches or less. From the 1940s through the mid 1980s, it was easy to differentiate between “few” and
“many. However, since then there has been so much crossing between the classes that there is a continuum
between the two classes. The lines at the edges of the range can be easily identied, but the ones in the middle
are difcult to classify. Branching is further complicated by “weak” branches, which appear on uniculm lines
in low populations. In most lines all of the nodes below the rst ower node have the potential to form branches.
With “true” branches, the longest branches are below the rst ower nodes, and other branches shorten further
down the plant. With “weak” branches, the longest branch is at the base of the plant, and the branches shorten
further up the plant. Weak branches get their name because they easily break down and end up below the com-
bine cutter bar. There are some lines with a propensity to form “spontaneous” branches which grow underneath
capsules in the middle of the capsule zone. These branches can set several capsules but normally stop owering
by the time that the main stem stops owering.
There is further confusion with branching due to regrowth. Certain lines have a propensity for restarting
growth after the main stem has stopped growing. Regrowth usually occurs in areas where conditions are such
that the plants have run out of moisture and/or fertility. If there is rain, some lines will form branches at the
bottom of the plant and these will ower and set capsules while the main stem and the older branches will not
start owering again. Regrowth is considered an anomaly and is not considered as part of the typical phenol-
ogy. However, it can cause confusion in that the end of mid bloom is dened as no owers on the branches.
Regrowth and the destruction of the apical meristem (insects or hail) are the only cases where the owering on
the branches extends beyond than the owering on the main stem.
Direct sunlight has a tremendous effect on the amount of branching. In order for a branch to form, light
needs to strike the leaf axil. In some uniculm lines there is no branching at all under all circumstances. However,
most uniculm and branched lines have the potential to branch in every leaf axil. Some lines have the potential
to form secondary branches on the branches, and a few have the potential for tertiary branches. In some lines,
if there is sunshine at the second pair of leaf axils of a branch, another branch will form, but in lower light, a
capsule will form. In order for a branch to continue growing, it needs light at the tip. The amount of light that
reaches the branches is dependent on population and/or leaf area. Higher populations and more leaf area shade
the leaf axils. True branches have the longest branches below the capsule zone because those branches have
more light and grow faster than the lower branches. Weak branches appear to form from the bottom of the stem
because as the lower leaves drop the light hits the lower leaf axils and the branch tip.
There are branches that are light seeking. In a high population they will grow out horizontally towards
the furrows and once they reach the direct sunlight will bend up and grow close to vertical. Other branches
will grow at the same angle regardless of sunlight. In high populations the leaf axil closest to the light may
develop a branch whereas the axil inside the canopy may not form a branch. There are some rare lines where
the branch on the inside of the canopy will grow around the stem and head towards the furrow parallel to the
branch on the opposite side of the plant. North of Uvalde, there is normally a cloud cover that clears between
10:00 and 11:00 a m . When a crop is planted in north/south rows, there are more branches on the west side that
receives more direct sunlight. Further north in the US there is more sunlight on the south rows planted east/
west resulting in more branching on the south side of the row. There are lines that will bend over in the wind
and not bend back up. On these lines, there are more branches on the upper part of the plant. Just as some
branches are light seeking, there are plants that are light seeking—the tips of these plants will bend out of the
canopy to reach the light and then grow vertically. On these types after defoliation, uniculm lines can appear
as branched from a distance. Other lines will only grow vertically to try to reach light.
Elevation, latitude, and row spacing can affect branching. With wider row spacing, more light gets to the
lower part of the plant. Elevation increases light intensity, and in northern latitudes there are longer days in the
summers providing more light. In the US, areas like Lubbock, Texas, with high elevation, northern latitude, and
wider row spacing have the most branching. Areas with less clouding have more branching as direct sunlight
has more effect than weak sunlight.
The International Plant Genetic Resources Institute (IPGRI), classies branching as non branching, basal
branching, top branching, and other (Anon 2004b). The top branching character has been eliminated from US
150
Issues in New Crops and New Uses
cultivars because they are prone to breaking over in high winds; the thick woody stem required to support the
plant can break the teeth on the cutter bars of the combine; and the plants are too tall for the combine auger to
feed the material into the combine—they bridge the header.
The width of the canopy is dependent on the branching habit, the angles of the branches, and the number
of branches. As mentioned there are branches that grow vertical after they reach the light creating narrower
rows than the lines where the branches continue growing at the same angle. There is variation on the angle
between the main stem and the branch. With more acute angles, the row is narrower. The angle varies from
the top branch to the bottom with each lower pair of branches having a wider angle. Thus, with more branches
the row is wider.
Capsules Per Leaf Axil
Capsules form from owers in the leaf axil from about 4–6 node pairs to the top of the plant. IGPRI (Anon
2004b) classies capsule arrangement as monocapsular or multicapsular. The author uses single (1) and triple
(3) capsules. The character is governed by a single gene, and the recessive allele produces triple capsules. The
IGPRI classication accounts for the fact that most triple capsule lines have single capsules at the bottom and
top of the plant, and rarely have three capsules in every node. There are germplasm lines primarily from China,
that can have 5 capsules per leaf axil in many nodes, and two lines have been found that can have 7 capsules per
leaf axil. Weiss (2000) reported up to 8 capsules. On triple capsule lines, on any given node there may be 1, 2, 3,
4, 5, 6, or 7 capsules. Nodes with greater than 3 capsules normally occur only in very low populations or at the
edge of a eld. On the other hand, single capsule lines under high light intensity may have as many as six node
pairs with triple capsules. The author uses single and triple capsule classication to reect the genetic makeup
of the line instead of the number of capsules per node on any one plant, which depends on the environment.
In the early 1940s D.G. Langham received germplasm from China that had triple capsules. Since his
Venezuelan cultivars had single capsules, he felt that he could triple the yield just by passing the character to the
Venezuelan germplasm. In the same year he received some germplasm with 4 carpels in the capsules translating
to 8 rows of seed instead of his 4 rows. He then felt it might be possible to increase the yield six fold. Obviously
there were source/sink issues, but a breeder must be allowed to dream. Axillary capsules on triple capsule lines
are rarely the size of the central capsules and have fewer seeds with lower 100 seed weight, resulting in lower
seed weight per capsule. In a 1999 Sesaco study, the axillary capsules averaged 79.4% of the weight of the cen-
tral capsule with a range of 69.9% to 87.3%. To date, in converting lines from 2 carpels to 4 carpels, the seed
weight per 4 carpel capsules is greater, but not double, and lower total capsules are formed on the plant.
As with branching, light has an effect on the formation of the capsules. On the single capsule lines, there
is a single capsule in the leaf axil anked by two nectaries. In a triple capsule line, the central ower forms rst
and opens 3–5 days before the axillary owers. In high populations the central open owers are in the sunlight
whereas as the plants keep growing, the leaves may shade the axillary owers. Although there is a very strong
correlation between the lack of light and a low number of axillary capsules, it is not known at what point the
light affects the development of a capsule. It may even be the result of another condition such as higher humid-
ity in the microclimate inside the canopy.
In low moisture and/or fertility conditions, the plants may not even form the axillary owers. In 1987 in
Arizona part of a eld of a triple capsule line did not get irrigated the rst time and as a result did not form any
of the axillary capsules. The whole eld had water on the second irrigation, and the plants then put on axillary
capsules on most of the nodes. This particular line put on small owers (without a lip) where there was a miss-
ing axillary capsule and formed a capsule. At the end of the crop, it was difcult to nd the demarcation line
between the two conditions without looking at the size of the axillary capsules within the missing irrigation
part being smaller. These no lip owers have been seen on many lines, and appear to be genetically controlled.
Other lines will not go back and put on missing axillary capsules under any conditions. Some triple capsule
lines will vary with the conditions: have single capsules in low moisture/fertility; then switch to triple capsules
under good conditions; and can go back to single capsules in poor conditions; other lines have started with triple,
gone to single, and back to triple. Lines with 4 changes in capsule number have not been observed.
Two studies have been done on the number of capsules on the plants. A 1998 Sesaco study looked at 51
lines studying the theoretical number of capsules that should have been formed on the capsule nodes with one
151
Edible Oilseeds, Grains, and Grain Legumes
capsule per node for single capsule lines and three capsules per node for triple capsule lines. Kang et al. (1985)
counted the number of owers and then the number of capsules. The results are shown in Table 6. The percent-
ages for triple capsules for Kang were higher because normally triple capsule lines put on single owers at the
bottom and top of the plant which the author was counting as potentially three capsules.
Maturity Class
Prior to 1988, the third character of the phenotype was plant height class. In those years the growing condi-
tions were similar and the height repeated each year. In 1988 due to planting in different locations in Texas, plant
heights varied considerably. There was an attempt to adjust the height to a standard, but there was still a lot of
variation with lines moving back and forth between classes. There was a general positive correlation between
plant height and maturity class, and there was less movement between maturity classes. Therefore, the third
character became maturity class. Since maturity depends so much on growing conditions, the lines still need
to be adjusted to a standard. S24 has been chosen as the standard (95 days to physiological maturity). If there
is more rain and higher fertility, S24 will mature later, and if rainfall and fertility are lower, S24 will mature
earlier. To standardize the cycle the 95 days is subtracted from the S24 maturity in a certain environment, and
this difference is used to adjust the maturities of all the other lines in that environment.
The maturity class is the sum of the rst three phases: vegetative, reproductive, and ripening. The drying
phase is not used because it is the one that is affected the most by the environment and in certain harvest strate-
gies, the plants are harvested at the end of the ripening phase. The effects of moisture, fertility, temperatures,
and other weather conditions will be discussed in each stage.
Leaves
The author has debated using leaf area as part of the phenotype. The leaves are generally opposite low
and alternate above, but can be opposite or alternate on the whole plant. In some lines plants have 3 opposite
leaves for part of the plant. In the opposite pattern the leaves rotate 90° each node pair; however, in low moisture
conditions, the opposite leaves will appear to spiral up the plant because the stem twists. The alternate leaves
have a slow spiral at the bottom of the plant and then will have a tighter spiral nearer the top. The lower leaves
are generally ovate to elliptic and then become lanceolate with narrower leaves in each node after the 6th node.
The top leaves can become linear in some lines. The lower leaves can be entire, lobed, cleft, parted, or divided.
The lowest leaves are entire with the rst non-entire leaf from the 3rd to 6th node (cultivar and population related).
After a few lobed leaves, the shape will revert to entire. The base of the leaf is rounded or obtuse on the lower
leaves and can reach attenuate in the upper leaves. The tip can vary from obtuse to acute to attenuate. The
edge of the leaves range from smooth to serrate to toothed.
Visually there are major differences within the germplasm. However, it is very difcult to quantify leaf
area. The number of leaves has an effect with some branched lines with smaller leaves having higher leaf areas
than uniculm lines with larger leaves. A short internode length has an effect in compacting the leaves and giving
the impression of more leaf area than longer internodes with more space. The timing of the data collection is
also important because the differences in rates of decrease in leaf sizes may end up with lower ratings on some
lines just by taking the data ten days later.
Table 6. Percentage of actual capsules per plant versus theoretical number of capsules.
Branching Capsule
Sesaco
capsules based on
number of nodes
Kang
capsules based on
number of owers
Single stem Single 91.6 80.0
Few branches Single 89.3 82.8
Many branches Single 89.4 -
Single stem Triple 59.2 7 7.1
Few branches Triple 51.6 61.4
152
Issues in New Crops and New Uses
Measuring leaves can be difcult. Bar-tel and Goldberg (1985) felt that using a specic leaf for measur-
ing was “impossible.” Despite the difculties in data collection leaves are very important and some form of
data collection is necessary, and the author measures one leaf at the 5th, 10th, and 15th pair of nodes. The size of
the leaves is determined from the seedling stage through the early-bloom stage of the reproductive phase. The
overall size of the leaves does not determine ultimate yield. There are very small leaf lines and very large leaf
lines that do not yield as high as the medium leaf lines. Fig. 1 shows the length and width of the leaf blades of
the current US commercial cultivars (Sesaco 25, D.R. Langham 2004a; Sesaco 26, D.R. Langham 2004b; Sesaco
28, D.R. Langham 2006a; and Sesaco 29, D.R. Langham 2006b) plus the smallest and largest leaves being car-
ried in the Sesaco germplasm. In some lines, the leaf blade length may continue getting larger further up the
plant through the 10th pair of nodes, but the width will always be narrower leading to a lower area. The width
of the 5th leaf can be dramatically larger in lobed leaves, but these leaves may not exceed the area of the entire
leaves. The gure is included to show the dramatic drop in leaf width between the 5th and 10th pair of nodes. It
should be noted that most lines have the capsules from the 5th to 6th pair of nodes.
The shape and the size of the leaves are controlled genetically. Lines with small leaves, lines with me-
dium leaves, and lines with large leaves planted side-by-side in multiple locations and environments will have
the same relative sizes within one place even though the leaves on the small leafed lines in one location can be
larger than the large leafed lines in another location. While it is clear that moisture and fertility increase leaf
size, the effects of population density, light, and degree days is not as clear. End plants of a row have larger
leaves than plants within the row, but is this due to wider space or greater moisture and fertility available to end
plants? Leaves in the shade inside the canopy of a row are smaller than the leaves in light on the opposite side
of the plant implying that light increases leaf size. It is assumed that low degree days decrease leaf size, but no
known experiment has proved it. In very sparse populations the lower leaves of the plants are larger than the
lower leaves of plants in crowded populations. In some lines in high sunlight, additional leaets form in the
leaf axil, and in many lines there are appendages along the petiole.
The sizes of the leaves will vary within the same cultivar based on the availability of moisture and fertil-
ity. Fig. 2 shows the variation within S26 grown under 6 environments with sample 1 having the least water
and nutrients and sample 6 the most, with the others in between. The petioles vary in length from the bottom
to the top of the plant parallel to the leaf width. However, there are some notable exceptions. There are lines
whose petioles lengthen to keep the leaf blade in direct sunlight. At the edge of a eld with no shading from
Fig. 1. Leaf dimensions of current Sesaco cultivars and other germplasm on the 5th, 10th,
and 15th node pair (LBL= leaf blade length and LW = leaf width).
0246810 12 14 16 18 20 22 24 26 28 30 32 34
ETH LW
S29 LW
S28 LW
S26 LW
S25 LW
KHA LW
ETH LBL
S29 LBL
S28 LBL
S26 LBL
S25 LBL
KHA LBL
Length (cm)
5th
10th
15th
153
Edible Oilseeds, Grains, and Grain Legumes
adjacent rows, on some lines it is possible to pick 50 leaves from the third pair of nodes from plants of equal
height, and all 50 leaves will have close to the same length and width, but the petiole length can have threefold
difference. In other lines the petiole lengths are all close. In opening the canopy, leaves on opposite sides of
the plant at the same node pair can have a different petiole length. In some lines, the petioles bend around the
stem allowing the leaf blade to reach the light.
Lines have different shades of leaf color throughout the growing cycle. During the vegetative and repro-
ductive phases the color is usually a shade of green, and then as the plants mature and begin to drop their leaves,
the color will turn to many shades of yellow/green, and rarely purple. There are many lines that have purple
on the upper surface of the petioles. The purple on the leaves, stems, and capsules can appear anywhere from
late bloom stage until the drying phase. There are sesame growing areas where researchers and farmers have a
narrow range of colors, and thus base phases and stages of growth on the shade of color. The color is controlled
genetically, and decisions made based on color on one continent can be wrong on another. The color of the
leaves usually matches the color of the stem and capsules. Within a line the shade of color is an indication of
what is happening with the plant.
Generally, when the plant is in normal growth it will be one shade of green. In two side-by-side elds,
the darker green will generally indicate better fertility.
If that eld starts getting a very dark green with almost a bluish hue, it is running out of moisture. When
there is a rain or irrigation, there will be a growth spurt leading to a lighter green.
If there has been a lot of rain the eld may turn yellowish green indicating that the roots are not getting
adequate oxygen. With aeration from cultivation, the leaves can green up within a matter of 6 hours.
The greening up from the soil drying out, without a cultivation, takes a longer time.
When the plants start to drop their leaves and turn yellow, the shades of yellow are an indication of the
late history of the plant. If the leaves turn a pale yellow and stay on the plant, it is an indication that the
plants ran out of nutrients. If the leaves turn a darker yellow and most of the leaves drop earlier than
normal, it is an indication that the plants ran out of moisture.
Roots
Very little research has been done on sesame roots, but they are very important to the phenology. Generally,
sesame plants have a strong tap root component and some brous roots. However, under differing conditions,
Fig. 2. Variation of leaf sizes in S26 based on the environment on the 5th, 10th, and 15th node
pair (LBL= leaf blade length and LW = leaf width).
0246810 12 14 16 18 20 22
S26 LW 6
S25 LW 5
S26 LW 4
S26 LW 3
S26 LW 2
S26 LW 1
S26 LBL 6
S26 LBL 5
S26 LBL 4
S26 LBL 3
S26 LBL 2
S26 LBL 1
Length (cm)
5th
10th
15th
154
Issues in New Crops and New Uses
the plants may have a stronger tap root or a stronger group of brous roots. Sesame is considered a drought
resistant species because the root will penetrate the deeper into the soil and nd moisture. However, every
crop needs moisture, and in a year with little deep moisture, sesame will not do as well. In the US the optimum
situation is to plant sesame into moisture and have no added moisture for about 30 days. Under these condi-
tions the roots will follow the moisture down, and sesame can withstand a lack of rain for the rest of the cycle.
In Venezuela, sesame is planted after the monsoon and will produce a crop with zero rain. If there are rains
or irrigations soon after planting, there will be more brous root development in the upper 30 cm of soil with
shorter tap roots. If this condition is followed by a drought, the plants can be in trouble as the moisture in the
top 30 cm is depleted, or a heavy rain can waterlog the plants and kill them.
Weiss (2000) cites Lea (1961) that in clay soils of Sudan, roots penetrate 25 cm in 10 days, 50 cm in 24 days,
and 75 cm in 50 days. Weiss states that roots will penetrate faster in sandy soils and grow more profusely; late
owering lines have deeper roots. Root growth is inhibited by relatively low salt concentrations. The author
has found a rough correlation between uniculm stems and single tap roots, and between branched stems and
branched tap roots. However, there are many exceptions in both directions.
Generally, the roots are as deep as the plants are tall. By the end of the reproductive phase, most of the
moisture is being drawn out of the 90–120 cm layer of soil. In Yuma, Arizona, in 1983, the Soil Conservation
Service placed neutron probes in sesame elds and found the deep moisture depleted while the surface of the
soil was almost muddy.
There is a condition known as wrinkled leaf (D.G. Langham 1945) where the blade in the leaves do not
ll in as the veins grow. Many have tried to isolate a virus, however it has been shown that when the roots
of certain lines hit a rock or a hard pan, the condition develops. Once that root nds a route down or a rain/
irrigation softens the hardpan, the condition disappears and is difcult to nd later in the cycle. The wrinkled
leaf is controlled genetically and can be carried further for many generations until the right conditions exist to
manifest itself. As will be discussed later, the root mass and leaf area need to be in balance, and the ways the
leaves adjust can be seen, but no research has shown how the roots adjust.
Time of Planting
The time of planting can have a major effect on the nal size of the plants and the yield. Mulkey et al.
(1987) and the author have carried out four time of planting studies in Uvalde as shown in Fig. 3. However, as
will be shown later, the soil temperature must be sufciently high at planting to germinate the seeds. Planting
in April is risky because the soil temperatures may be too low, and the one farmer that was able to get a stand in
March had a very poor yield. The data clearly shows that the yields decrease the later the crop is planted. The
previous assumption has been that degree days are critical for yield. However, in comparing the decrease in
yield to degree days there is no clear correlation. Fig. 4 shows the accumulated degree days through 100 days
after planting when the seeds have lled and are at physiological maturity. Degree days are in centigrade and
represent the sum of the mean daily temperatures for 100 days using a base of 0°C.
The degree day data for the years of the experiments in Fig. 3 was not available on the internet, but the
patterns in terms of peak units can be extracted to have a similar curve. In the four years in Fig. 4, there are
considerable differences for early planted sesame, but by the middle of May the accumulated degree days do not
vary as much. The temperatures in April are more erratic than the later temperatures. The correlation between
the yields in Fig. 3 and the accumulated degree days in Fig. 4 is R=0.613. Beech (1985) cites Kostrinski (1955)
who determined that 2,700 accumulated degree days (DD) is necessary to produce maximum yields in sesame.
He also cites Ding (1983) that 2,300 DD together with 750 to 770 hr of sunshine are necessary. Beech (1995)
states that although the Australian objective had been 2,700 DD, most of the areas in Australia do not meet this
requirement. Having grown sesame successfully in areas without 2,700, Beech felt that the optimum number of
DD could be lowered signicantly by breeding lines with lower heat requirements. He found lines from Japan
and Korea that needed lower DD, but for lines from Mexico such as Yori, he determined the DD required was
2,900. The author agrees with the Beech theory because in the US yields of 1,500 kg/ha have been obtained in
northern Texas with 2,400 DD using germplasm that is more suited to lower temperatures.
In order to relate the yields shown in Fig. 3 to the accumulated daylight hours for 100 days from date of
planting in Uvalde, Fig. 5 was derived. The correlation between the yields in Fig. 3 and the daylength hours in
155
Edible Oilseeds, Grains, and Grain Legumes
Fig. 5 is R=0.864. The accumulated daylight hours have a higher correlation to the higher yields in Fig. 3 than
the accumulated degree days. In northern Texas the accumulated daylight hours are even longer than in Uvalde
(with a max of 1403 daylight hours), and higher daylight hours may make up for some of the lower degree days
in that area.
As shown in Table 7, in time of planting studies in the Sudan, Tanzania, India, and Korea (Weiss 2000),
Korea with two systems of planting (Lee 1986), and Ciudad Obregon, Mexico (G. Musa 1988, pers. commun.),
the earlier the sesame is planted, the higher the yield. The data from all the environments in similar latitudes
as the growing areas in the US (Mexico and Korea) shows the same pattern as the Uvalde data in that yields of
crops planted in April are lower than the yields of those planted in May and then there is sharp drop-off.
Rate of Growth of Irrigated Sesame
Fig. 6 shows the rate of growth of three cultivars under irrigation in 2004 in Uvalde. Generally, the plants
are about 30 cm in the rst 35 days, and then almost double in height in the next 7 days and continue this rapid
growth until 70 days when the plants begin to shut down. Note that ‘S29’ has a faster rate of growth and yet it
shuts down before ‘S26. The rate of growth is not related to physiological maturity. In rainfed conditions, the
nal plant heights are lower, but the pattern of very slow growth followed by fast growth during the reproductive
phase exists under all conditions. In order to compare the rate of growth diagram to the phases, Table 8 shows
the phases of the 3 cultivars in Fig. 6. Sesame grows slowly in the beginning because it is using its resources
to put down the root that is following the moisture. In seeing that the internodes shorten from bottom to top,
there has been a misconception that once owering begins, the rate of growth slows down. As can be seen in
Fig 6, the rate is fairly constant from the start to end of owering.
Fig. 3. Effects of dates of planting on yield in Uvalde,
Texas.
Fig. 4. Accumulated degree days (C°) for 100 days
from different dates of planting in Uvalde, Texas.
Fig. 5. Accumulated daylight hours for 100 days from
different dates of planting in Uvalde, Texas.
Fig. 6. Rate of growth of 3 US cultivars in adjacent
plots.
156
Issues in New Crops and New Uses
Basis for Number of Days to and Within Phases/Stages
The description of each phase and stage provides the number of days for that phase or stage. In the phases,
the number of days will be in terms of all Sesaco lines and ‘S26’ between 2000 and 2005, while in the stages
the number of days will be in terms of ‘S26’ planted in Uvalde in 2004. ‘S26’ is used as the example because
it has been the major cultivar planted in this time period, and thus there is much more commercial experience.
Table 9 shows data on ‘S26’ from 2000 to 2005. The 2003 nursery is not included because it was damaged by
hail in the juvenile stage and by the eye of a hurricane in the mid bloom stage. The hail destroyed 30% of the
leaf surface, and the hurricane leaned the crop over but did not lodge it.
Any one cultivar will be different depending on the growing conditions for that eld and the weather for
that year. The timing of the rains can have as much an effect as the quantity of the rains. For example, a rain at
30 days from planting for one eld can help that eld while an adjacent eld just planted may get crusted in and
not be able to germinate. As can be seen there are wide variations in total days to direct harvest, ranging from
114 to 154 days. In 2000, there was a rain substituting
for the rst post-plant irrigation that prevented adding
the application of the post-plant nitrogen. The lack of
nitrogen terminated the crop earlier. Then, there was
no rain from the end of owering to drydown, which
accelerated complete drydown. In 2001 and 2002
there were rains in the reproductive phase eliminat-
ing the need for the third irrigation. In 2001 through
2005, there were rains between maturity and drydown
lengthening this period.
VEGETATIVE PHASE
The vegetative phase is divided into four stages:
germination, seedling, juvenile, and pre-reproduc-
tive.
Denition: From the time the seeds imbibe the moisture
to 50% of the plants with open owers. The 50%
point is somewhat subjective because it is difcult to
differentiate in terms of percentages, i.e., there is little
visual difference between 40%, 50%, or 60%.
In the same location, with different planting
dates, lines will ower at about the same time. In
a 1990 time of planting Sesaco study in Uvalde, 80
lines began owering an average of 40 days in the
May 19 planting, 42 days in the June 12 planting, and
41 days in the July 14 planting. In 2006 some elds
were planted in late August, and ‘S26’ started ower-
ing much earlier—at the 4th pair of nodes at 30 days
instead of the 6th pair at 40 days. This anomaly needs
further study. Some lines from the tropics are pho-
tosensitive and will only begin owering at a certain
number of hours of sunlight. No photosensitive lines
were included in the 1990 data above.
In a 1998–1999 Sesaco study in Uvalde, the num-
ber of days within the vegetative phase were grouped
by phenotype, and there were no signicant differ-
ences as shown in Table 10. The differences between
phenotypes are more pronounced in the next phase.
Table 7. Effects on time of planting on yield in diverse
environments.
Author Country Planting date
Yield
(k g/ha)
Wei s s Sudan Mid-June 1096
Mid-July 346
Mid-August 293
Tanzania Mid-Jan 973
Mid-Feb 835
Mid-Mar 521
India (Bengal) Mid-May 325
Mid-June 101
Mid-July 45
Korea Mid-Apr 677
Mid-May 76 4
Mid-June 437
Musa Mexico 10-Apr 765
20-Apr 885
10-May 985
30-May 766
20-Jun 408
10-Jul 285
Lee Korea 1-May 670
(Conventional) 15-May 540
25-May 480
15-Jun 370
25-Jul 50
(Vinyl mulchz)1-May 1270
15-May 1110
25-May 670
15-Jun 500
25-Jul 101
zIn Korea most farmers plant under a vinyl cover to
increase soil temperatures and reduce weeds.
157
Edible Oilseeds, Grains, and Grain Legumes
Table 8. Number of days from planting and within phases for cultivars
in the plots in Fig. 6.
Days from planting Days within phase
Phase S24 S26 S29 S24 S26 S29
Vege t a t i ve 42 44 40 42 44 40
Reproductive 87 90 82 45 46 42
Ripening 103 105 102 16 15 20
Drying 135 145 147 32 40 45
Table 9. Data on S26 between 2000 and 2005 planted in research nurseries in Uvalde, Texas.
Planting date
2000 2001 2002 2004 2005
Variabl e 05/28 06/06 06/09 05/17 05/20
Previous crop Wheat Wheat Wheat Fallow Fallow
Pre-plant nitrogen (kg/ha) 33.6 33.6 33.6 33.6 33.6
No. pre-plant irrigations 1 1 1 1 1
Post-plant nitrogen (kg/ha) 033.6 33.6 33.6 33.6
No. post-plant irrigations 2 2 2 3 3
Yield sampling (kg/ha) 1,421 1,696 1,642 1,692 1,808
Branching style Many Many Many Many Many
No. capsules/leaf axil 1 1 1 1 1
Days to owering 41 40 42 44 43
Days to ower termination 79 75 81 90 89
Days to physiological maturity 96 103 10 2 106 106
Days to direct harvest 114 154 145 146 141
Plant height (cm) 128 143 165 174 162
First capsule height (cm) 52 49 61 64 55
Capsule zone length (cm) 76 94 104 110 107
No. capsule node pairs on main stem 23 29 29 31 30
Leaf length (cm) at designated
node pair
5th 30 25 29
10th 20 19 27
15th 19 15 18
Leaf blade length (cm) at des-
ignated node pair
5th 17 16 15
10th 14 14 18
15th 14 13 14
Leaf width (cm) at designated
node pair
5th 20 15 17
10th 7 4 7
15th 3 2 3
Capsule length (cm) 2.2 2.3 2.3 2.4 2.3
Seed wt/capsule (g) 0.219 0.254 0.234 0.280 0.239
Hundred seed wt (g) 0.326 0.328 0.337 0.352 0.344
Time to End of Phase from Planting: 29–59 days for all lines, 40–44 days for ‘S26’.
Length of Time within Phase: 29–59 days for all lines, 40–44 days for ‘S26’.
158
Issues in New Crops and New Uses
Factors that Shorten the Phase: Lower fertility and moisture and higher temperatures.
Factors that Lengthen the Phase: Higher fertility and moisture and cooler temperatures.
Germination Stage
Denition: From the time the seed meets moisture until most of the seedlings emerge from the soil. In the US
most sesame is planted into the moisture, but there are a few cases where the seed is planted dry soil and then
watered up.
Time from Planting: 3–5 days. For seed planted about 2.5 cm deep in good moisture, in South Texas, the low
end is usually 4–5 days in late April and 3–4 days planted in mid May. In northern Texas and Oklahoma, the
low end is 4–5 when days planted in late May and 3–4 days if planted in late June.
Length of Time: 3–5 days.
Description: Germination is one of the most important stages because if there is a poor stand, no subsequent
farmer action or weather condition can produce a high yield. The threshold temperature for sesame is 15.9°C
(Angus et al. 1980). In the early years of US commercial production the recommended minimum planting
temperature was 23.9°C (Kinman 1955). Weiss (1971) states that should temperatures fall below 20°C for any
length of time, germination may be inhibited and will certainly be delayed. In planting hundreds of thousands
of hectares of sesame since the 1980s, the current recommended minimum temperature is 21°C (Langham
et al. 2006). This does not mean that sesame will not germinate at a lower temperature. The recommended
temperature is based on a reasonable probability of achieving a full stand. Higher temperatures increase the
rate of germination and increase the probability of achieving a full stand.
Temperatures between 25–27°C encourage a rapid germination, initial growth, and ower formation (Weiss
1971). The present author has found that with soil temperatures around 25°C, the seed imbibes enough moisture
that it is soft within 24 hr, and the seed can be pushed out of the seed coat with a bulge at the tip of the seed.
Between 24 and 48 hr, the radicle emerges and within 12 hr of emerging, the root will push down and start fol-
lowing the moisture. Between 36 and 60 hr the seedling will start pushing up through the soil. Between 3 and
5 days, the seedling emerges from the soil.
Fig. 7–9 show the importance of temperature in germination. The 1967 author study was done in Petri
dishes in a growth chamber with light plus the higher temperature for 14 hr and darkness and the lower tem-
perature for 10 hr. Fig. 7 shows the number of days from the time that the seeds meet the moisture until the
radicle pushes out of the tip of the seed. The effect of temperature is very pronounced. The seeds where the
temperature dipped below 21°C had radicle emergence, but nowhere near as high as the higher temperatures in
terms of percentage of seeds that reached emergence or the emergence speed.
Fig. 8 shows the number of days until the root has developed secondary hairs and the seedling started push-
Table 10. Vegetative phase length by phenotype.
Vegetative phase length (days)
1998 1999
Branching Capsule Mean Range Mean Range
Uniculm Single 41 39–48 42 4045
Triple 40 36–50 43 41– 4 6
Few branches Single 39 36 44 42 3846
Triple 41 38–50 42 3945
Many branches Single 40 36 49 43 41– 4 7
All 40 36–50 42 3847
159
Edible Oilseeds, Grains, and Grain Legumes
ing up. At 18.3–21°C most of the seeds whose radicles emerged also had secondary roots develop on the main
root and the seedling starts pushing up, but at 12.8–15.6°C, none of the seeds reached that point even though
37% had emerged radicles. Many did develop some hairs but the plants did not push up. At higher temperatures
most of the seedlings had root hairs but at 23.9–26.7°C it took longer than at 29.4–32.2°C.
Fig. 9 shows the number of days until the seedlings ip over and the cotyledons open up. At the 18.3–21.1°C
and 12.8–15.6°C treatments after 14 days very few seeds had open cotyledons. In several sets, the materials were
left in the chamber until 21 days without any further change. In this third stage of development, the temperatures
lead to a wider gap between the two high temperature curves.
The above study shows the sensitivity to temperature, but the 14/10 hr split with a 2.8°C temperature swing
does not approximate the temperature uctuation over several days as shown in Fig. 10 (uvalde.tamu.edu/weather,
accessed 5 April 2005). Depending on the amount of sunlight the differences between the low and the high soil
temperatures can be as much as 13°C in one day in Uvalde soils.
Different genotypes react differently to the low temperatures with some emerging faster than others at
low temperatures but all emerging at about the same time at high temperatures (Bennett et al. 1997). They also
showed that the type and depth of soil made a difference on speed of emergence by genotypes. The present
author plants plots by volume instead of seed count, and thus there are fewer seeds planted in a large seeded
line. In most environments the stands are comparable regardless of seed size. However, in marginal germina-
tion conditions there are differences. In compacted soils, soils with a thin crust from a rain, or seeds planted
at deeper depths, there is a positive correlation between large seed and stand. If the moisture is marginal or at
Fig. 7. Rate of emergence of the radicle from the tip of
the seed under different temperature conditions.
Fig. 8. Rate of development of secondary hairs and
seedlings pushing up under different temperature
conditions.
Fig. 9. Rate of cotyledons opening under different
temperature conditions.
Fig. 10. Air and soil temperature at Batesville, Texas,
1–4 April, 2005.
160
Issues in New Crops and New Uses
shallow planting depths, there is a positive correlation between small seed and stand. In marginal moisture, the
seeds may imbibe water and swell, but if there is not enough water, they will dry out and germinate with a later
rain or irrigation. However, if the seed swells to the point that the radicle pushes through the seed coat before
not having enough moisture to continue, the seed will rot and will not germinate.
The germination stage is very vulnerable to rain, which can create a crust in the soil over the sesame. If
the seedlings are caught in the crust, there is no hope and the sesame should be replanted. If the seedlings are
below the crust, there is a possibility that the crust will crack and allow the seedlings to emerge. If the soil
types are such that there is no cracking, the ability to break through is dependent on the thickness of the crust.
Once the seedlings have pushed against the crust for several days, they will not have the resources to push to
the surface.
Factors that Shorten Stage:
Shallower planting (however if too shallow, may lose moisture and not germinate).
Reduced soil compaction (however, some soil types lose moisture quickly under no compaction).
Higher seeding rates (sesame has small seeds, and more seeds together have more push).
Higher temperatures.
Factors that Lengthen Stage:
The inverse of the above: deeper planting, increased soil compaction, lower seeding rates, and lower
temperatures.
There are some root pruning herbicides such as pendimethalin and triuralin that also lengthen the
stage.
Seedling Stage
Denition: From the seedling emergence point until the point where the third set of true leaves is the same
length as the second set of true leaves.
Time from Planting: From about 6 days to 25 days.
Length of Time: About three weeks.
Description: In 2003, about 600 ha were planted between 2 and 29 May in Batesville, Texas, under pivots. Fig.
11 is based on observations from those elds. Zero denotes cotyledons with no visible true leaves. A leaf pair is
counted when it exceeds the length of the previous pair. Up to that point, decimals are used, e.g., 2.5 indicates
that the third pair of leaves is 50% the length of the
second pair. This system can be used to estimate the
number of days since planting in a eld.
When the seedlings rst emerge, the cotyledons
are yellow and inverted in a crook. Within several
hours, the cotyledons straighten up, open and the shoot
primordia start growing. Within several days, the 1st
set of true leaves will be visible, but will not equal the
size of the cotyledons until about 11 days after plant-
ing. From the 1st through the 5th or 6th leaves, the leaf
area will get larger and then after that the leaves will
generally get smaller all the way to the top of the plant.
The 2nd set of true leaves is visible about 13 days after
planting, and it exceeds the length of the 1st leaves
in about 18 days. The 3rd set of true leaves becomes
Fig. 11. Rate of development of true leaves on com-
mercial sesame in 2003 in Batesville, Texas.
161
Edible Oilseeds, Grains, and Grain Legumes
visible at about the same time and exceeds the length of the 2nd about 25 days after planting. At this point the
plants are about 15 cm tall. By the time the 3rd leaves equal the 2nd leaves, the 4th set is visible, and then before
the 4th set equals the 3rd, the 5th and 6th sets are visible.
The seedling stage is the most vulnerable stage to perils. At the beginning of the stage, leaf eating insects
can destroy the plants, but towards the end, the plants can usually overcome the damage. High winds with
blowing sand can sandblast the plants or cover the seedlings. Rains with running water can cover the seedlings.
With no weed control, most weeds will outgrow the sesame plants and cover them.
This is the stage where the plants will start differentiating in size. The rst seedlings that emerge will
normally have the largest cotyledons and will accelerate their growth the fastest. This will lead to larger leaves
and to longer roots. The plants with longer roots will compete against the later emerged plants by pulling more
moisture and fertility. The larger leaves have an effect in a high stand in that they will begin to shade the later
emerged plants and reduce the amount of light they receive. The larger plants will become dominant plants and
will form the canopy. The minor plants will be below the canopy. Depending on cultivar, some minor plants
will turn to the weaker light in the furrows and when they emerge into the sunlight will turn vertical. They
will still be minor plants, but they can be productive. In other cultivars, the minor plants will stay within the
canopy and will produce few capsules and may die. This later phenomenon is known as self-thinning. In some
cases when there is a weather phenomenon that damages the dominant plants (e.g., hail or lodging), the minor
plants will emerge and become the dominant plants. In some cases with limited moisture, all of the plants will
exhaust the available moisture and the plants will be very short and have few capsules.
There are some occasions when all of the seedlings emerge at relatively the same time. In this case, no one
seedling has a clear advantage, and this can lead to abnormal growth. This group of plants will compete equally
for light, resulting in much taller plants. Similarly, roots will compete equally, but will end up shallower than
normal as the plants shift their resources to making stems and leaves. This group of plants will eventually be
shorter than the rest in the eld as the resources are divided equally with less water and nutrients to each plant.
This group will also mature and dry down sooner than the rest of the eld.
The time of day that the seedlings emerge can be a factor. Seedlings that emerge in the evening just before
dark do not have an advantage over seedlings that emerge 12 hr later the next morning. However, because of the
sunlight these morning seedlings will have a clear advantage over the seedlings that emerge 12 hr later. There
are some soils that crack allowing light to the seedling before it reaches the surface. These seedlings may turn
green and if given enough of a crack the cotyledons may invert before reaching the surface. These will gener-
ally emerge unless they are covered by rain (closing the crack) or by blowing sand.
Factors that Shorten Stage:
Larger cotyledon size. Within a cultivar with the same size seeds, the faster the seedlings emerge, the
larger the cotyledons because there has been less expenditure of stored materials to emerge. Between
cultivars, larger seeds have larger cotyledons.
Higher temperatures.
Factors that Lengthen Stage:
Rain or irrigation that reduces the oxygen available to the roots and compacts the soil. Sesame does
better when there is no rain or irrigation until about 30 days after planting as long as there is sufcient
moisture (see below).
Lack of fertility. This is particularly evident in elds that have been planted after a disced in crop where
there has been no additional fertilizer, and the plant matter is tying up the nutrients.
Juvenile Stage
Denition: From third true leaves until the rst oral buds are visible. The growing shoot can be pulled apart
showing buds earlier, but this stage ends when the buds are visible without touching the plants.
Time from Planting: From about 26 days to 37 days.
162
Issues in New Crops and New Uses
Length of Time: 1.5 weeks.
Description: The juvenile stage is short and could have been combined with the seedling stage; however, this is
an important 1.5 weeks to the farmer because this is the time the plants are tall enough for directed spraying with
herbicides. It is also the rst time that a farmer should consider moisture conditions for the rst irrigation.
From the start of this stage multiple leaf sets are visible, and the number of days between leaf sets equaling
the previous set decreases. High moisture, fertility, and temperatures increase the plant height and the size of
the leaves at this stage, but the length of the stage remains basically the same.
As mentioned before, this stage is very dramatic because it is in stark contrast to the seedling stage where
after 26 days from planting, the plants are only 15 cm tall. Within this stage in the next 11 days the plants can
double in size to be 30 cm tall; and then double again in the next stage.
This is the last stage where a low level of stress will not hurt nal production. By holding back irrigations,
the roots will continue to follow the moisture deeper into the soil, and the stems and leaves will not be as large.
The deeper roots give the plants more exibility in withstanding late irrigations, and the smaller stems and
leaves reduce the potential to lodge and allow more photosynthates to go to the reproductive stage. However,
the plants should not be stressed to the point that they will shed leaves and convert to a rainfed architecture.
Factors that Shorten Stage: Drought. There have been many examples in ood or furrow irrigation where
the irrigation water does not reach the end of the eld. That dry end will start producing buds earlier than the
irrigated part of the eld.
Factors that Lengthen Stage:
Rain or irrigation that cuts off oxygen to the roots. Sesame does better when there is no rain or irriga-
tion until after this stage as long as there is sufcient moisture in the soil.
Cool night temperatures.
Low soil fertility. As in the seedling stage, this is particularly evident in elds that have been planted
after a disced in crop where there has been no additional fertilizer, and the plant material is tying up
the minerals.
Pre-reproductive Stage
Denition: From rst oral buds until 50% of the plants have open owers.
Time from Planting: From about 38 days to 44 days.
Length of Time: About 1 week.
Description: The rst oral buds appear in the leaf axils from the 4th to the 6th set of true leaves, depending on
cultivar. Although it is possible earlier than 38 days to pull the leaves down and look closely at a bud forming,
rst oral buds are considered when the buds are visible without touching the plants. The buds start out greenish
yellow and as they get closer to the day they will open, they will turn more cream-yellow. On the evening
before they open, they will turn a whiter color, pick up purple hue, and will double in size from then until the
next morning when they open.
This is the most important farming stage to optimize production because it coincides with the last time that
a tractor can enter a eld to cultivate and/or apply fertilizer. It also signals the latest time for the rst irrigation
unless there have been adequate rains.
From this stage until the late bloom stage it is important not to stress the crop. Although the plants stress
when they do not get adequate moisture, sesame is well adapted to going into a drought. It will drop the lower
leaves in order to equalize the amount of transpiration with the amount of available moisture. If the crop is
stressed to this point, irrigations will not bring back the leaves and depending how long the plants have been
stressed, an irrigation may be counter-productive. It may set the plants back, may cause shedding of owers,
and may kill the plants.
163
Edible Oilseeds, Grains, and Grain Legumes
Factors that Shorten or Lengthen Stage: There are no known factors that will shorten or lengthen the stage.
Factors that Accelerate the Onset of the Stage:
Dry portions of the eld will bud rst.
High degree days will accelerate the start of rst buds.
By this stage within a eld there can be considerable variation in the number of days until oral buds.
Dominant plants will bud rst.
Factors that Delay the Onset of the Stage:
High moisture and fertility.
Hail can damage plants and set them back delaying the start of buds.
Cool night temperatures.
REPRODUCTIVE PHASE
The reproductive phase is divided into three stages: early bloom, mid bloom, and late bloom.
Denition: From 50% of the plants owering to 90% ower termination. As in owering, the ower termination
measure is subjective in that it is difcult to distinguish between 85% and 95%. At the end of the owering
period, the rate that plant puts out open owers is reduced. Thus, there can be more than 30% of plants with
buds and still have reached this measure since there will not be more than 10% owering any one day. Another
problem is that under low moisture conditions a eld noted as terminated may restart owering if there is
sufcient rain.
Within the same location with different planting dates, the later the planting the earlier most lines will
stop owering. In a 1990 time of planting Sesaco study in Uvalde, 80 lines stopped owering an average of 97
days after planting in the May 19 planting, 86 days in the June 12 planting, and 84 days in the July 14 planting.
There are lines that stop owering earlier than expected in northern latitudes, and this early termination must
be controlled genetically since certain parents and their progeny exhibit the same pattern. However, it is not
known if this is due to photoperiod or cool temperatures.
In a 1998 and 1999 Sesaco study in Uvalde, the number of days within the reproductive phase was bro-
ken out by phenotype, as shown in Table 11. Within each phenotype with more moisture and higher fertility
in 1998, there were more days in the reproductive phase than the 1999 nursery. For each branching style, the
triple capsules had fewer days in the reproductive phase. For the number of capsules, in the uniculm and few
branch phenotypes there were fewer days in the few branch phenotypes, but the pattern was not the same for
the many branch types. In isogenic lines, the zx43 version had 6 owering days fewer than the zx41 version,
and a zx13 version had 5 owering days fewer than the zx11 version. Similar patterns have been seen in F2
segregating populations.
Time to Start of Phase from Planting: 29–59 days for all lines, 4044 days for ‘S2 6’.
Table 11. Reproductive phase length by phenotype.
Reproductive phase length (days)
1998 1999
Branching Capsule Mean Range Mean Range
Uniculm Single 50 38–56 39 27–44
Triple 47 38 –53 35 30–46
Few branches Single 46 38– 63 34 2 5 – 41
Triple 42 3649 32 26–38
Many branches Single 47 39–56 37 28 43
All 46 36–63 35 25–46
164
Issues in New Crops and New Uses
Time to End of Phase from Planting: 56–116 days for all lines, and 75–90 days for ‘S26’.
Length of Time within Phase: 27–52 days for all commercial lines, and 35–46 days for ‘S26. For ‘S26’ the short
owering period was in 2000 with lower fertility, fewer irrigations, and no rain; the long owering period was
in 2004 with more water from rains.
Factors that Shorten the Phase: Lower fertility and moisture and higher temperatures.
Factors that Lengthen the Phase: Higher fertility and moisture and lower temperatures.
Early Bloom Stage
Denition: From 50% owering until capsules have formed in 5 node pairs.
Time from Planting: From about 45 days to 52 days.
Length of Time: About 1 week.
Factors that Shorten or Lengthen Stage: There are no known factors that signicantly shorten or lengthen the
stage.
Description: Sesame owers have ve petals with the lower petal being longer, and forming what is known as
the lip. The lip is folded over the top of the ower keeping it closed to around dawn when it opens and forms
a landing strip for bees. Sesame is self-pollinating, but differing rates of cross pollination have been reported.
D.G. Langham (1944) reported 4.6 cross pollination in Venezuela. Yermanos (1980) cited the following cross
pollination rates: 1–17% by Ali and Alam (1933) and Sikka and Gupta (1949) in India, 3–15% by Martinez and
Quilantan (1963) in Mexico, and 3–6% by Khidir (1973) in Sudan. In his own experience in the US, Yermanos
found less than 1% when the sesame was surrounded by cotton and other crops. In Moreno, California, he
found 68% in a eld where the sesame was the only blooming plant in a semi-arid area. Ashri (2007) cited Van
Rheenen who had rates between 2.7 and 51.7% in Nigeria. The present author found considerable cross pollination
in the Arizona nurseries where many farmers maintained bees for pollinating other seed crops, but little cross
pollination in the Texas nurseries. Recent research has indicated an increase in yield with high populations of
bees (Mazzani 1999; Sarker 2004).
Pollination normally takes place around the time the owers open. Flowers open later in cool and/or over-
cast days. In the afternoon the corolla tubes drop off the ower, but the ovary that will form the capsule, stays
on the plant. There are cultivar differences when the corolla will drop, and there are some lines where it does
not drop and stays attached as the capsule forms. Within 3 days the capsule will be visible and will lengthen
to about 2.5 cm within a week. There are varietal differences in the rate of elongation. The seeds form inside
the capsules.
In watching the crop during this stage, the rst owers rarely make capsules, but often in looking at the
plants later, there are capsules in these nodes. Given the right conditions, the plants will put on another ower
at that leaf axil and form a capsule. In this stage, and in the late bloom stage there are many nodes with miss-
ing capsules. In crops under no stress, there are fewer gaps. Often a gap will indicate a stress such as heavy
rains that cut down the oxygen to the roots, winds that blows owers off the stem, or a cold spell that prevents
fertilization. In a drought, the owers have a weaker attachment to the stem, and can blow off even in a mild
wind. ‘S26’ is a branched single capsule line and on the whole plant it would be expected that there would be a
failure of 1 out of every 10 owers. The distribution of missing capsules is not even, with most of the missing
capsules at the lower main stem and the branches. In the 1998 Sesaco study on the 5 lines similar to ‘S26, the
lower main stem segment had 84% actual capsules versus potential capsules; the middle main stem had 97%;
the upper main stem had 100%; the lower branches had 86%; and the upper branches had 84%.
In the Western Hemisphere, most lines have a phyllotaxis of opposite leaves: each leaf of a pair is on
opposite sides of the stem forming a pair of nodes. Each subsequent pair of nodes rotates 90° and is on the op-
165
Edible Oilseeds, Grains, and Grain Legumes
posite side of the stem. The opposite rotation is essential to allow the capsules from the lower leaves to rest in
between the leaf axils of the leaves above thus allowing longer capsules with shorter internodes. In some lines
the leaves are offset in an alternate pattern and generally have longer internodes.
In a high population, from this stage forward the plants may drop the lower leaves that are not receiving
light. This is not considered stress. Those leaves are transpiring moisture and without light, not performing
optimum photosynthesis. If leaves in daylight are dropping, it is an indication of insufcient moisture and/or
fertility. However, in the dry areas of Texas, it is expected that late in the day there will be a certain amount of
wilting with the plants fully recovered by morning.
Mid Bloom Stage
Denition: From 5 node pairs of capsules until the branches and minor plants (plants of lower stature, growing
in part under the canopy of the taller plants) stop owering.
Time from Planting: From about 53 to 81 days.
Length of Time: About 4 weeks.
Description: The beginning of this stage normally coincides with the branches starting to ower. However, the
5 node indicator is used because the start of owering on the branches depends on population. In order for a
branch to grow and become productive sunlight must shine on the branch. In very dense populations, the plants
at the center of the canopy and the minor plants may not have any branches. In thin populations, the branches
will start putting on owers and capsules before the 5 pairs of capsule nodes indicator. In lines with no branches
and triple capsules, the expression of triple capsules is usually stronger after the 4th node pair. The 5th node is
not as signicant in lines with no branches and single capsules.
This stage is the most productive stage because both the main stem and branches are putting on owers/
capsules. In a study in Thailand Suddhiyam et al. (2001, pers. commun. 2005) counted the number of ow-
ers every day on two lines. UB1 has many branches and a single capsule while UB2 is a uniculm with single
capsule. The study on UB1 is the average of 4 seasons, and the study on UB2 is the average of 2 seasons. The
results in Fig. 12 show that on UB1 80% of the owers occur in the rst three weeks of mid bloom (4 weeks
after owering commences), and in UB2 83% of the owers occur in the same three weeks. Therefore, even
though owering can drag out for as many as 10 weeks, most of the production (90%) is put on the plant in the
rst 4 weeks of owering.
Kang et al. (1985) in Korea did a similar study for four phenotypes as shown in Fig. 13. The branched
single capsule phenotype had 79% of the owers in the rst three weeks after owering.
As stated before, the mid bloom stage is the worst
time to stress the crop by untimely irrigations. Delay-
ing too long will force the crop to try to adjust to a per-
ceived drought, but irrigating back too soon is almost as
bad. Sesame prefers not to have too much water at any
time, and standing water even for a short time can kill
sesame. Over-irrigation can reduce yields more than
under-irrigation.
If there is an unavoidable delay in irrigation, it may
be better to stop irrigating. When the plants are stressed
for moisture, the lower leaves will wilt more each day
and the top of the plant may also droop. Within 7–10
days of severe wilting, the plant will drop its lower
leaves thereby reducing the transpiration rates. De-
pending on multiple factors, the plants will drop enough
leaves that the moisture in the soil can support the plant,
Fig. 12. Percentage of owers produced for each
week in study of two lines in Thailand.
166
Issues in New Crops and New Uses
and the plants will wilt less each day. The plants may also stop owering and will accelerate the lling of the
seeds. If the plants in this state are irrigated, there is more stress than before in that the leaves cannot transpire
enough moisture out of the soil to get oxygen to the roots, and the plants can die.
One sign that the plants are running out of moisture is the number of owers that are open in a day. In
single capsule lines in mid bloom each owering head (the main stem and each branch) will have 2 owers
open per day. There are instances where the main stem may have 3 owers open. It is not unusual to have
branches with less than 2 owers in dense populations. However, when a large percentage of the main stems
are down to a single or no open ower, the plants are running out of moisture and/or nutrients. After a rain or
irrigation, the number of owers per owering head will increase, but it takes time for the plants to restart. On
triple capsule lines, the main stem will normally have 6 open owers per day—two central owers and 2–4
nodes down four axillary owers. There can be as many as 9 owers open on a main stem. There are generally
fewer open owers on the branches.
At the end of the cycle, it is possible to know the moisture history of the plants by looking at the internode
lengths. The lengths get progressively shorter from bottom to top of the plant, but they reduce at a discernable
rate. If there is an abrupt shortening of the internodes, the plants went into moisture stress at that time. When
the plants do get the water, the lengths can remain about the same for several node pairs or can actually increase.
Similarly, the capsule length will decrease going into a drought and increase coming out of the drought.
Factors that Shorten and Lengthen Stage: This stage is almost totally dependent on the availability of moisture
and fertility. The greater the amount, the longer the owering period. However, too long a stage can be
counterproductive. Sesame is an indeterminate species that will continue putting on owers as long as there is
moisture, fertility, and sufcient heat. In 27 years of growing commercial sesame in the US, Sesaco has only
encountered three occasions when the crop continued owering while the lower capsules began to dry. In all
cases, there was a tremendous amount of residual fertility in the ground from previous crops, and the farmers
continued adding water. Although very high fertility and moisture adds more potential yield, it generally will
lead to lower actual yield for one or more of the following reasons:
The capsules at the bottom of the plant will mature and dry while the plant is still owering, and by the
time the plant is dry enough for harvest, some of the seed in the bottom of the plant is lost due to shat-
tering. The amount of shattering is cultivar related with most cultivars in the world losing considerable
seed while the US improved cultivars have minimal losses.
Longer growing periods mean taller plants that are more susceptible to lodging and more difcult to
combine.
In the fall, the drying weather deteriorates. There are fewer hours of sunshine for drying, and in most
of the sesame growing areas there is more rainfall in the fall. These rains lead to dews in the morn-
ing and evening. In some areas with natural
high humidity such as Uvalde, the window for
combining in late September is about 8 hr and
can be as low as 4 hr by mid-November. This
window problem does not apply to areas such
as West Texas with very low humidity and
constant winds where on good days the crop
can be combined for most of the day even in
late fall.
Although the present cultivars are more shatter
resistant than older cultivars, they do shatter
more the longer they remain in the eld.
The top capsules produce lower seed weight
per capsule and the quality is not as high, and
thus the additional production has more dam-
aged seed with lower test weight, which can
lead to discounts.
Fig. 13. Percentage of owers produced for each week
in study of four phenotypes in Korea.
167
Edible Oilseeds, Grains, and Grain Legumes
Late Bloom Stage
Denition: From branches/minor plants not owering until 90% of the plants in a stand have no open owers.
Time from Planting: About 82 to 90 days.
Length of Time: A little over 1 week.
Description: The beginning of this stage on branched lines is when the branches stop owering. In uniculm lines,
the minor plants will stop owering. The onset of this stage generally coincides with the plants running out of
moisture and/or nutrients. As in mid bloom, there will be progressively fewer and fewer open owers per day.
This is a very difcult stage to determine because at times it is very abrupt and clear and under other
conditions, it stretches out over a long time. With a given line in different years, one year it appears the stage
has just commenced, and the next week it has ended. In another year, it appears that the stage has commenced,
and the next week the eld still has the same level of open owers because of a rain. In Texas and Oklahoma,
the rainfall is generally accompanied by lightning, and thus the moisture will often bring down nitrogen from
the atmosphere slightly increasing fertility and the available moisture and nutrients keep owering at a reduced
rate for as much as two weeks.
The end of the stage is when 90% of the main stems do not have an open ower. In some cases, there may
be as many as 30% of the plants that still have unopened buds, and a third of those will have open owers on
any given day appearing as 90% no open owers. In most cases there will be fewer and fewer plants each day
with buds and/or open owers, but in rare cases the 30% can keep going for several weeks as do the Thailand
cultivars in Fig. 12 above. It is very important that ower termination be determined in the mornings before
the corollas have fallen. There are lines that drop their corollas as early as 1:00 PM and then appear to be no
longer owering.
At this stage, many plants will start having yellow leaves at the bottom, and they will drop the lower leaves
without the leaves wilting. This is the start of natural self-defoliation to be discussed in the ripening phase
below.
At the top of the plants there is a higher percentage of owers that do not become capsules than on the
lower parts of the plants. The amount is both genetic and environmental. There are lines that never produce
capsules at the top, and lines that may or may not produce them, depending on moisture and fertility. The level
of temperatures that begin to affect growth in the nal stages as yet has not been determined because no two
years are alike. In some years, there are cold fronts that come through and then temperatures return to normal
levels and there is little effect. In other years, the weather is generally cooler, and the night temperatures appear
to be more important than the day temperatures. The sesame plants will indicate cooler nights by the owers
containing more anthocyanins; they are deeper purple. The rule of thumb is that sesame is affected by night
temperatures of 4–10°C. Genotypes react differently to cold: some will stop owering; some will ower but
will not set capsules and/or seeds; some will ower and set capsules and seeds.
There are several patterns of termination: indeterminate, determinate due to lack of moisture/fertility,
and determinate. For many years almost all of the sesame introduced from Asia was indeterminate, but recent
introductions are not. On indeterminate lines, the tops of the plants are still owering while the lower capsules
are drying down. In some of these lines, the plants drop the leaves before the capsules dry down, but in others,
the dry capsules can be in the leaf axil of a very green leaf. In Asia there are many cultivars where the farm-
ers cut the plants that are still in mid bloom stage because they want to place the plants in shocks before the
capsules dry and the seed falls out. In this type of harvest there is a continuum of mature seed to immature
seed. Even though it is easy to separate the very immature, there is a point where semi-mature seed is included
in the nal product.
Since the 1940s many cultivars have been developed where the plants stop owering on their own when
they run out of moisture and/or nutrients. All US commercial cultivars fall into this category. However, two
cultivars were developed that in two different environments owered much longer, and there were dry capsules
while the plants were still owering. In those cases, the soil was unusually fertile from previous vegetable crops,
168
Issues in New Crops and New Uses
and the roots found the water table 180 to 300 cm deep. In strips adjacent to the commercial elds, the 18 other
lines stopped owering before there were dry capsules. It is not known if the roots of these lines did not reach
the water table, or if there is another mechanism that stopped owering, or if there was another mechanism that
delayed dry capsules.
An indeterminate crop has both advantages and disadvantages (Beech 1985). The main advantage is
sesame’s ability to continue to grow and produce harvestable yields as long as soil water supply and temperature
are adequate. The main disadvantage is asynchrony of maturity. In conditions in the US, sesame’s indeter-
minate nature has a great advantage in that the reproductive stage (average 38 days, ranging from 27–52 days)
can overcome many environmental conditions that reduce yields substantially in other crops were the owering
stage is short.
Ashri (1985) discovered a botanic determinate mutant controlled by a single recessive gene. The last node
at the top of the main stem was a ower which became a capsule. The ower had six fused lobes instead of the
normal 5 with no lip and six stamens and jutted vertically upwards. Ashri distributed the gene throughout the
world and thousands of crosses were made with germplasm in many countries. However, the mutant produced
only 3–5 pairs of nodes before terminating and then would produce branches that in turn would terminate in a
ower. This process would continue and the nal effect was that the capsules on the main stem would dry down
while the outer branches were still owering. Several breeders developed lines that would stop owering before
dry capsules and several developed uniculm lines that would not branch. However, no line was developed with
a higher yield than local cultivars (Day et al. 2002). R. Brigham had one plant that had 7 pairs of nodes (pers.
obser.) but his breeding program ended before the seed from the plant could be planted to see if the character
would repeat. The present author did hundreds of crosses without being able to increase the number of nodes.
The determinate mutation continues to be worked on because it produces an intriguing phenotype: a tremendous
number of branches with a short capsule zone resembling the nal architecture of safower. Ashri’s original
mutant is a parent in several cultivars released in Korea by C.W. Kang.
In 2003, the author found a line where some of the plants terminated in a capsule and by 2005 there was a
pure line. In 2006, more attention was placed on the late bloom stage and a similar ower to Ashri’s was found
on the nal node. The main difference in this line was that there were 20–25 node pairs on the main stem, no
branches, no dry capsules at the end of owering, and a reasonable yield. The line has been crossed with the
Ashri mutant to determine if both have the same gene.
As with any crop, there will be areas of the eld that have stopped owering while others are still in mid-
bloom. In sandier soils, the plants will generally stop owering sooner. In low areas, in some years there will
be too much moisture which will damage the plants and that will be the rst area to stop owering while in other
years, the same area may have the optimum amount of moisture and will be the last to stop owering. Areas
with high populations will stop owering rst.
Factors that Shorten Stage: Very hot period with low humidity.
Factors that Lengthen Stage: Cool weather with high humidity and rain.
RIPENING PHASE
The ripening phase is not divided into stages. Technically, the ripening process begins in the reproductive
phase.
Denition: From 90% ower termination until physiological maturity. Physiological maturity (PM) is the date
at which 3/4 of the capsules on the main stem have seed with nal color and a dark tip. In many lines, the seed
will also have a dark seed line on one side.
The concept of physiological maturity (PM) in sesame was developed by M.L. Kinman in the 1950s
(pers. commun.) in order to determine the earliest date that the plants could be cut and still harvest over 95%
of the potential yield. When the seed has nal color, the seed can germinate. If the plant is cut at physiological
maturity, most of the seed above the 3/4 mark will continue maturing sufcient for germination, but may be
lighter. Since even in a fully mature plant, the seed weight produced at the top of the plant is low, this loss of
169
Edible Oilseeds, Grains, and Grain Legumes
seed weight does not seriously affect the potential seed yield of the plant. PM is important in northern US crops
where there is a potential for an early frost or freeze. After PM the majority of the yield can be harvested even
if the plants were terminated by cold.
In Uvalde, the rule of thumb is that physiological maturity will move up 6–7 node pairs per week below
the 75% PM level, and 4–5 node pairs per week above the 75% level. In West Texas at higher elevations with
cooler nights, the weekly rate has not been determined, but in 2003, with limited data, it appeared that just
below the 75% level, the progress was about 3–4 node pairs per week, and above it, 1–2 node pairs per week.
More data is necessary to quantify the rates in both locations, but from additional observations made in 2004
through 2006, there is no doubt that ripening is slower in cooler temperatures.
In a 1990 time of planting Sesaco study in Uvalde, 80 lines had a mean of 120 days to PM in the May 19
planting, 107 days in the June 12 planting, and 102 days in the July 14 planting. In a 1998 and 1999 Sesaco
studies in Uvalde, the number of days within the ripening phase were analyzed by phenotype, as shown in Table
12. Within each phenotype with more moisture and fertility in 1998, the ripening phase was longer in the 1998
nursery. Although there were patterns in the reproductive phase, there are no clear patterns between the pheno-
types in the ripening phase. In isogenic lines, even though the zx43 version matured 8 days earlier it only had
3 fewer ripening days than the zx41 version. A zx13 version had 1 fewer ripening day than the zx11 version.
Time to Start of Phase from Planting: 56–116 days for all lines, 75–90 days for ‘S2 6’.
Time to End of Phase from Planting: 77–140 days for all lines, and 96-106 days for ‘S26.
Length of Time within Phase: (14)–54 days for all, 15–28 days for S26. There are negative values in the low end
because lines from Asia which have mature (and dry) capsules before the plants stop owering.
Description: Technically, sesame is in the ripening phase from the mid-bloom stage through the early late
drydown stage. To date, there is no universal denition of mature seed. Some dene the seed as mature when
it can germinate. Others dene the seed as mature when it reaches its maximum dry weight. Within a capsule,
the seed matures within 25 to 63 days (P. Suddhiyam, pers. commun., 2005) from the day the owers open. The
seeds in the lower capsules take longer to mature than those in the upper capsules—51.0 versus 29.4 days (Day
et al. 2002). There has been little research to determine how much difference there is between cultivars. Both
of these denitions require tagging owers and then sequentially harvesting them and processing them.
For farming, Sesaco denes the seed as mature when the placenta attachment between the seed and the
capsule dries, and the seed coat gets its nal color (turns from milky white to a buff color) (Langham et al. 2006).
In US lines on one side of the seed, there is a visible seed line from the tip to the middle arc. There are lines
from Korea and China without this line at maturity. The Sesaco system is conservative; capsules at the top of
the plant whose seeds have not put on the nal color have viable seeds that have germinated in laboratory tests.
Generally, the seeds get their color rst at the lower capsules and maturity progresses up the stem. There are
a few exceptions where the lowest capsules do not get their color rst. There are lines that put on the lowest
capsule later in the cycle. However, it is not important because the seed in these lower capsules always put on
color before physiological maturity.
Table 12. Ripening phase length by phenotype.
Ripening phase length (days)
1998 1999
Branching Capsule Mean Range Mean Range
Uniculm Single 16 7–24 13 9–22
Triple 18 14–2 3 14 3–19
Few branches Single 20 7–32 16 8–28
Triple 19 14 –21 15 8 –19
Many branches Single 19 14 28 13 8 –19
All 18 7–32 14 3–28
170
Issues in New Crops and New Uses
In a 1998 Sesaco study, it was shown that the dry weight of the seed in different parts of the plant differs
as shown in Table 13. The number of node pairs on the main stem was counted and divided by 3 to divide the
main stem into lower, middle, and upper segments. The branches were pushed to the main stem and the branch
segment to the top of the lower main stem segment were designated as the lower branch segment. The rest of
the branches segments above this point were designated as the upper branch segment. There were only two
lines that had node pairs on the branches above the middle main stem segment. There can be as much as 13%
difference between the smallest and largest seed on the plants when it is divided by large segments. The seed
in the very top capsules is usually considerably smaller than the seed in the middle stem.
During this phase, most of the leaves fall off the plants. Sesame starts self-defoliation in late bloom stage
and ends in the initial drydown stage. Generally, leaves will turn yellowish green (some lines go to a pale yel-
low or a deep yellow) before dropping. In many lines the lowest leaves turn yellowish when the canopy blocks
the light, and they will drop even while the plants are in full bloom. As mentioned above the leaves may drop
due to drought. Dropping of leaves because of shade or drought is not considered the maturity self-defoliation.
As the plant stops owering and matures, the leaves will drop from the bottom of the plant to the top. There
are a few US lines where the plants hang on to a few node pairs of lower leaves while dropping the leaves in the
middle node pairs. However, in these lines, the lower leaves drop as the plants enter the drying phase. In some
elds, the upper leaves can hang on longer providing some photosynthesis for seed ll in the upper capsules.
These will also drop long before the combine. If the plant is killed prematurely by insects or disease, the leaves
will dry on the plant and will generally only fall after considerable rain and wind.
There are many defoliation patterns in the world sesame germplasm. W. Wongyai from Thailand has
developed a series of lines that defoliate while green. Her objective is to reduce the amount of transpiration
after the leaves have provided the nutrients for the capsules at that level. This character has been conrmed to
occur in both the US and Thai growing conditions. This is a good trait for crops that are cut at maturity, but
in the US where the crop is not cut until the plants are dry, early drop of leaves allows more light to the ground
and can bring on weeds. There are lines that do not drop the leaves even when the lower capsules have dried.
These can cause problems in drying in that farmers cut the plants to avoid losing the seed, and yet the leaves
force a longer drydown in a shock, or push up the moisture in the threshed seed.
In the US, the leaf below the capsule will drop before the capsule matures and the capsule and plant will
turn a yellowish green. At PM certain genotypes have a shade of yellowish green with some with a lot more
green and others with a lot more yellow. In order to use the color as a cue to look for PM, the researcher needs
to be familiar with the color of that cultivar. For example, ‘S27’ is more green than yellow; ‘S29’ is more pale
yellow;S25’ is a deeper yellow; and ‘S24’/ S26’/S28’ a balanced yellow green. There are lines that are dark
green capsules with mature seed and lines that are very light yellow with immature seeds.
After the plants have stopped owering, there is a danger that the plants will have regrowth, and the plants
will start owering again. Regrowth occurs primarily when the plants have stopped owering earlier than normal
because the plants ran out of moisture and/or nutrients. Fields that go to normal termination rarely will restart.
There are three types of regrowth, top (restarts at the tops of the main stems), middle (branches emerge from
the middle of the main stem), and bottom (branches start in the axils of other branches or below the branches).
There are lines that show spontaneous branching whereby branches start in the middle of the capsule zone under
Table 13. Hundred seed weight in different plant segments by phenotype.
Hundred seed wt (g)
Branching Capsule AllzLMS MMS UMS LBR UBR
Uniculm Single 0.298 0.296 0.305 0.290
Few branches Single 0.286 0.290 0.295 0.283 0.271 0.269
Many branches Single 0.305 0.322 0.322 0.306 0.286 0.284
Uniculm Triple 0.271 0.276 0.270 0.264
Few branches Triple 0.245 0.2 41 0.246 0.246 0.237 0.252
zAll = average of whole plant, LMS = lower main stem, MMS=middle main stem,
UMS=upper middle stem, LBR=lower branches, UBR=upper branches.
171
Edible Oilseeds, Grains, and Grain Legumes
capsules. However, this is not considered regrowth because spontaneous branches start during owering and
stop owering before the top of the main stem stops owering. In regrowth, the plants look indeterminate in
that the lower capsules dry while the plants are still owering.
The onset of regrowth needs further study because there are conicting patterns. In 1991 there was a
drought from planting time, which stopped owering in all but a few lines. With a rain, all the lines that had
stopped went into regrowth. In 2006 there was a drought resulting in no owers on most lines, and yet after a
rain, the plants started owering again without going to regrowth. The lines owered longer than normal, but
the lower capsules did not dry down while the plants were owering. There is a positive correlation between
tendency to go to regrowth and the lines that have the longest delayed shattering (discussed in full maturity
stage). In some years lines with a tendency to go to regrowth will be the only lines to go to regrowth and yet
under similar conditions none may go to regrowth. To date no line has been found that will not go to regrowth
under the proper conditions. Fields will rarely go to regrowth in cooler night temperatures.
Factors that Shorten Phase: Lower moisture and/or fertility and higher temperatures.
Factors that Lengthen Phase: Higher moisture and/or fertility and lower temperatures.
DRYING PHASE
The drying phase is divided into three stages: full maturity, initial drydown, and late drydown.
Denition: From physiological maturity until complete drydown when 99% of the plants are dry above where
the cutter bar would hit the plants. This is a difcult date to determine because there are few elds that have
uniform soils and some parts of the eld will always be dry ahead of others.
One of the problems with a freeze is a false indication of the extent of the drydown. With natural drydown,
as the stems dry down, they will turn brown, and lose most of the moisture. After a freeze, the plants will turn
brown within days, but will still have too much moisture to combine. Green plants will take 7–10 days to dry
down after a freeze.
With the exception of the lines mentioned before with dry capsules during owering, all harvest scenarios
are done in the drying phase. The rst four options below are usually done in the full maturity stage, while the
last option is cut after the late drydown stage.
In the majority of the world, sesame plants are cut manually and shocked. Although the ideal is to cut
the plants before the rst dry capsules, in large elds it is not possible to cut all the plants when they
are mature without dry capsules. In many areas, farmers will cut plants that are ready and plants that
are not will be cut later. In parts of Africa, the plant bundles are tied to a fence. In parts of India and
Turkey, the cut plants are taken to a drying oor where less seed is lost during drying. When the shocks
are dry, the plants are turned upside down over plastic or a blanket and the seed falls out. In Mexico,
the shocks are fed into a combine.
In Korea and Thailand, some farmers cut the plants with a rice cutter and place them into shocks. When
dry the plants are fed into stationary threshers.
In Venezuela, the plants are cut with a binder after PM and are manually shocked. When dry the shocks
are fed into a combine by a hydraulic attachment to the front of the combine.
In the US, for many years the plants were cut with a swather and left in a windrow. Upon drying they
were combined with pickup attachment.
Currently in the US and Australia, the plants are cut after the late drydown stage when the plants are
completely dry. Desiccants have been used in the full maturity or initial drydown stages to accelerate
the drying.
Time to Start of Phase from Planting: 79–140 days for all lines, 96–105 days for ‘S26.
Time to End of Phase from Planting: 102–181 days for all lines, and 114–154 days for ‘S26’.
Length of Time within Phase: 11–57 days for all lines, 18–51 days for ‘S26.
172
Issues in New Crops and New Uses
Factors that Shorten the Phase:
Lower fertility and moisture.
Higher temperatures.
Lower humidity.
Sunshine.
Constant winds.
A frost may accelerate drydown, but often depends on the stage of the plant and the length of time the
plants are subjected to the low temperature. A frost in the early stages will not accelerate drydown as
much as the same frost in the late stages.
A hard freeze will kill the plants and they will start drying down quickly.
Factors that Lengthen the Phase:
Higher fertility and moisture.
Lower temperatures.
High humidity.
Cloudy days, fogs, and dews.
Later planting leads to later drydown as the days are getting shorter providing fewer drying hours.
Full Maturity Stage
Denition: From physiological maturity until 90% of all the plants have all seeds mature. Sesaco does not take
data on days to all seeds mature and thus the following range is an estimate based on one year of data.
Time from Planting: From about 107 to 112 days.
Length of Time: About 1 week.
Description: With direct harvest without desiccation, this stage is not important. With swathing or desiccation,
the plants will be killed and the seeds will no longer ll. At the end of this stage, the plants will have the highest
potential yield and can be terminated to accelerate drydown. However, since the capsules in the top 2–3 node
pairs contribute little seed, the practical time may be at some point between PM and all seeds mature. In essence
the purpose of swathing and desiccation is to harvest sooner, and thus the practical time may be better.
Tables 14 and 15 show the relative importance of the parts of the plant as they relate to yield. These are
from the same 1998 Sesaco study as in the 100 seed weight in Table 13. Table 14 shows that the capsules in
the upper third of the plant produce lower seed per capsule and that the capsules in the branches produce even
less. However, it is still yield.
In experimental elds where there is thinning, the seed weight per capsule would be expected to be fairly
uniform, but in unthinned elds, there is a lot of variation between dominant plants and minor plants. In a
2004 Sesaco study, two capsules were harvested from the middle of the capsule zone on 50 consecutive plants
of the same cultivar in a row. As can be seen in Fig. 14, there is considerable variation between dominant and
minor plants.
Table 15 shows the percentage of seed weight in each plant part from the 1998 Sesaco study. In the up-
per portion of the main stem there is lower percentage of seed than would be implied from the seed weight per
capsule in Table 13 because there are fewer capsules in the upper portion of the plant. Although this signicant
lower seed weight per capsule in the branches, there are enough branches and capsules resulting in a signicant
amount of seed in the branches (an average of 36.4%), and even more in lower populations.
The ratio of seed in the main stem versus the branches changes considerably with population with less
seed in the branches in high populations and more seed in the branches in low populations.
Under some conditions there is vivipary in sesame—the seeds will germinate in the capsules. Not only
are the germinated seeds lost, but the root of the seedling binds the rest of the seed. Many researchers have felt
that the opening of the capsules allows water to enter and germinate the seed. Actually, the opposite occurs.
Seeds in open capsules do not germinate because the moisture will evaporate out of the capsule before the seed
173
Edible Oilseeds, Grains, and Grain Legumes
can germinate. The vivipary occurs in closed capsules. It is believed that this is a dispersal mechanism to open
the capsule and allow the seed to fall out. Vivipary is controlled genetically with some lines having a greater
propensity than others. Vivipary is rare in the US because normally at harvest the temperatures are below
21°C—the minimum germination temperature. Vivipary is more common in tropical temperatures, particularly
Ashri’s determinate mutant. There are lines such as Cola de Borrego from Mexico (Ashri 1985) and UB1 from
Thailand (Suddhiyam et al. 2001) whose seeds are dormant after maturity for several months after harvest.
Factors that Shorten Phase:
At this point it is not known if lower moisture and/or fertility shortens the phase. There is not enough
data.
High temperatures.
Table 14. Seed weight per capsule in different plant segments by phenotype.
Seed weight/capsule (g)
Branching Capsule AllzLMS MMS UMS LBR UBR
Uniculm Single 0.206 0.196 0.220 0.203
Few branches Single 0.195 0.194 0.215 0.203 0.148 0.158
Many branches Single 0.204 0.215 0.242 0.225 0.168 0.18 7
Uniculm Triple 0.156 0.157 0.163 0.140
Few branches Triple 0.131 0.14 0 0.141 0.122 0 .114 0.116
zAll = average of whole plant, LMS = lower main stem, MMS=middle main stem,
UMS=upper middle stem, LBR=lower branches, UBR=upper branches.
Table 15. Percent of total seed yield in different plant segments by phenotype.
Percent of total seed yield
Branching Capsule LMSzMMS UMS MS LBR UBR BR
Uniculm Single 31. 2 37.1 31.7 10 0.0
Few branches Single 27.1 28.8 23.7 79.6 9.9 10.5 20.4
Many branches Single 22.4 23.5 17.7 63.6 15.9 20.5 36.4
Uniculm Triple 25.5 41.8 32.7 100.0
Few branches Triple 19.1 32.5 26.9 78.5 10.6 10.9 21. 5
zLMS = lower main stem, MMS=middle main stem, UMS=upper middle stem, MS=total in
main stem, LBR=lower branches, UBR=upper branches, BR=total in branches
Fig. 14. Seed weight per middle main stem capsule from 50 consecutive plants.
174
Issues in New Crops and New Uses
Factors that Lengthen Phase: Low temperatures—see description of ripening phase.
Initial Drydown Stage
Denition: From all seeds mature until 10% of the plants have one dry capsule. The plants used should be green
plants that have natural drydown excluding plants that have died from a disease. In windy areas, the plants
may rub against each other and break down capsules. These will become dry, but these are not considered as
dry capsules.
Time from Planting: from 113 to 126 days.
Length of Time: About 2 weeks.
Description: Earlier, lines were described that have dry capsules at the bottom of the plant while the plant is
still owering. Since the 1940s lines have been selected that do not have open until the plants are past PM (D.G.
Langham and Rodriguez 1945). The time between PM and rst dry capsule is known as the harvest window
and US cultivars have been developed with as much as 21 days of harvest window. A wide window is important
when the crop is cut at maturity to decrease the amount of seed lost from the dry capsules. However, if the crop
is going to harvest at complete drydown, a long harvest window is a disadvantage in that it will delay harvest.
The main stem will generally have dry capsules before the branches, but the branches will generally dry
down before the main stem. The lower capsules dry rst with the top capsules drying last. Parts of the stems
will dry before all of the capsules are dry. The pattern of stem drydown differs in that in some cases the middle
of the stem dries rst and then goes in both directions, in others the top stem dries rst and goes down, and in
others the bottom stem just below the capsules dries rst and goes up and down. In any sequence the lowest
part of the plant between the lowest capsules and the root is the last to dry.
The only exception to the lowest part drying last is when the plant succumbs to root rot, then the drying
will be from the very bottom of the plant up, and the drydown will be much faster. There are three root rots
(Fusarium, Phytophtora, and Macrophomina) that affect US sesame. The newest cultivars have much greater
tolerance than cultivars developed in the mid 1990s, but there are still plants that die earlier than the rest. Plants
are more susceptible to the root rots when there is stress: low soil moisture at the seedling stage when the root
is racing to keep up with the moisture; the use of some root pruning herbicides which will not kill the plant but
will offer a point of entry for the root rot; moisture stress in both directions—too little or standing water. Plants
that die should not be counted in the 10% of plants with dry capsules.
Factors that Shorten the Phase: The same as described in the drying phase paragraph above—lower fertility
and moisture, higher degree days, lower humidity, sunshine, constant winds, frost, and freeze.
Factors that Lengthen the Phase: The same as described in the drying phase paragraph above—higher fertility
and moisture, lower degree days, high humidity, cloudy days, fogs, dews, and later planting.
Late Drydown Stage
Denition: From rst capsule drydown until enough drydown for a combine to produce 6% moisture seed.
Time from Planting: From 127–146 days.
Length of Time: About 3 weeks.
Description: Of all of the phases, the nal drydown phase is the most variable in terms of length of time in the
phase. If the reproductive phase is shorter because of lack of fertility, this phase will have a shorter time from
planting but will not necessarily change in terms of length of time in the phase. However, if the reproductive
phase is shorter because of lack of moisture, this phase will have shorter time from planting and length of
time in the phase. On the other hand, the fall has more rain than the summer in Texas and Oklahoma, and the
175
Edible Oilseeds, Grains, and Grain Legumes
reproductive phase can be shortened, but sufcient, late rains will keep the length within the drydown phase
the same. Table 16 is an extract of Table 9 and it shows how one cultivar (‘S26’) can have radically different
starting and end points for each phase. In 2000 rains prevented the second fertilizer application and there were
no rains during the drydown phase. As a result there was 40 days difference in total drydown compared to 2001
where there were rains throughout drydown.
When the capsules are dry, they open at the tip allowing the seed to fall out. For 5,000 years sesame has
been harvested manually. The farmers cut the plants when green and shock the plants to dry. The sesame is then
inverted and struck to shake out the seed. Farmers have thrown out any mutations that keep the seed from just
falling out when the capsules are inverted. Two closed capsule mutants have been found: the indehiscent allele
id was discovered by D.G. Langham in 1943 (D.G. Langham 1946) and the seamless allele gs was discovered by
D.R. Langham and D.G. Langham in 1986 (D.R. Langham 2001). Although initially these were thought to be
the solution for mechanization, the combines damaged the seed too much. The indehiscent gene was distributed
throughout the world with hundreds of breeders trying to reduce the damage. In the 1950s there was hope in
combining the indehiscent allele with a character known as “papershell” capsules (Culp 1960). However, when
they were combined in Sesaco 01, it was still not enough. In combining closed capsules, the concaves must be
closed and the cylinder speed increased. Many operators have added rasp bars to increase the threshing surface.
Essentially, each capsule must have opposing forces on each side and some seed in each capsule is damaged.
In addition, the cutting action often crimps the opening created on the capsule and the seed cannot ow out.
Sesame seeds have a thin seed coat and contain over 50% oil and can be damaged easily. Even if the seeds are
not broken, they can be bruised, which will create free fatty acids that will turn the seed rancid.
Sesaco bred non-dehiscent sesame (D.R. Langham 2000, 2001; D.R. Langham and T. Wiemers 2002) by
joining 6 characters so that the seed is held in the capsules until in the combine and then most of the seed is
threshed out of the capsules in the feeder housing of the combine. The concaves can be opened and the cylinder
speed slowed down. The key was the development of a stronger placenta attachment by accumulating genes to
improve the original placenta attachment discovered by D.G. Langham (Langham et al. 1956). In addition, there
were genes with minimal opening and a gene that held the two halves of the capsule together until the combine.
There is an adhesion that is similar to a post-it note that holds the halves but not too much. There are lines that
have better shatter resistance than the present cultivars, but they hold the seed in the capsules in the combines.
Capsules with tips that are more closed also are susceptible to forming mold in the capsules. Non-dehiscent
sesame is a balance between the capsules holding the seed until the combine cuts the plants but then releasing
the seed inside the combine with minimal force.
Non-dehiscence is controlled by multiple genes and is difcult to move over to shattering lines requiring
many crosses and large segregating populations in the F2. There are some shattering lines from China and
Russia that have yet to produce a progeny with non-dehiscence despite viewing tens of thousands of F2 plants.
Crossing between two non-dehiscent lines usually results in non-dehiscence in the F1, but in other pairs the
shatter resistance mechanisms break down. Through the 2006 season, non-dehiscence has been incorporated
into over 1,000 lines with varied genotypes and phenotypes.
Many researchers continue to try to close up the capsule at drydown. However, there is tremendous advan-
tage in opening the capsule in terms of accelerating harvest. The seed at maturity has about 60% moisture and
for combining it has to reach 6%. With a closed capsule, all of this moisture must travel from the seed through
the capsule wall whereas with open capsules, the moisture can escape out the top. In Yuma, in 1982 two lines
Table 16. Cycle dates that delineate phases in ‘S26’ planted between 2000 and 2004 in research
nurseries in Uvalde, TX.
Stage 2000 2001 2002 2004 2005 Max–Min
Days to owering 41 40 42 44 43 4
Days to ower termination 79 75 81 90 89 15
Days to physiological maturity (PM) 96 103 102 10 6 106 10
Days to direct harvest 114 154 145 14 6 141 40
Direct harvest—PM 18 51 43 40 35 33
176
Issues in New Crops and New Uses
were swathed the same day—one with a closed capsule (indehiscent) and the other with an open capsule. There
were rains on both windrows, which delayed harvest. When the open capsule windrow was ready to combine,
the closed capsule windrow had too much moisture in the seed. Additional rains kept the combines out of the
indehiscent eld for 6 weeks. At that point there were weeds growing through the windrow further complicating
harvest. When combining direct in subsequent years, if the combines were operating in the eld before a rain,
the combines could re-enter the open capsule lines 3–5 days earlier than the closed capsule lines. The capsule
walls absorb moisture and it is easier to dry out from both sides of the capsule than just from the outside. The
longer that a crop is left in the eld, the longer that it is in danger.
In US sesame with combine harvest, the consistency of the stem has many effects on the phenology. In
many US eld crops, the harvesting equipment does not take the stem into the machine (corn and cotton) or
only takes the top part of the plant (wheat, sunowers, safower, and sorghum). In these crops, strong stems
can be bred to prevent lodging. In crops such as sesame, soybeans, other types of beans, and guar, the majority
of the plant enters the combine. In order to breed for lodging resistance in sesame, there has to be a balance
between creating a stem that will reduce lodging and still cut without damaging the cutter bars, be pliable enough
to move through augers, and break up in the combine. Woodier stems take longer in the vegetative and early
reproductive stages because the plants are using resources to produce more lignins. These woodier stems hold
their moisture longer and take longer to dry down in the drydown stage.
Factors that Shorten the Phase: The same as described in the drying phase paragraph above—lower fertility
and moisture, higher degree days, lower humidity, sunshine, constant winds, frost, and freeze.
Factors that Lengthen the Phase: The same as described in the drying phase paragraph above—higher fertility
and moisture, lower degree days, high humidity, cloudy days, fogs, dews, and later planting. At the end of a
day the sesame may be below 6%, but the seed will rehydrate during the night. With a dew, the capsule can be
hydrated and close up. It will take time in the morning for the sesame to dry out again.
ABIOTIC EFFECTS ON PHENOLOGY
Light
As explained before, light is essential in branch and capsule development. In Uvalde time of planting
studies there is a high positive correlation between yield and total light units in the vegetative and reproductive
phases. In planting the same cultivar at the same latitude in Oklahoma and Korea, the plants are taller in Korea
under similar moisture and fertility inputs (pers. obser.). One possible explanation is that in Korea there is less
sunshine in the Suweon area due to smog and cloudy days. In planting the seed 20 miles apart in Uvalde under
similar moisture and fertility inputs, the plants to the south are usually shorter. One possible explanation is
that in the north the elds are near the hills, and the sun usually breaks out of the overcast 2–3 hours later in the
morning. It appears that weak light promotes stem elongation and strong sunshine reduces it; however, it does
not appear to change the number of days in the stages.
Daylength
There is photoperiodism in sesame where short-day sesame cultivars grown in long-day conditions will
start owering much later and produce larger plants and conversely long-day cultivars grown in short-day con-
ditions will have accelerated owering and produce shorter plants (Joshi 1961). In the US, most introductions
from Africa and South America will not start owering for 50–70 days depending on the planting date, and the
plants can be as tall as 245 cm (D.R. Langham and Wiemers 2002). One of the major cultivars in Venezuela
was Aceitera which in Venezuela was 65 cm tall and matured in 92 days (Mazzani 1962). In Arizona, Aceitera
in 1990 was 215 cm tall and matured in 137 days. In 1967 the author took the best US lines and planted them in
two nurseries in South India. The plants were very short, started and ended owering earlier, and had signicant
lower yield compared to the local lines.
As discussed above, in the 1990 date of planting Sesaco study the number of days to owering of US lines
does not vary considerably with daylength in plantings from May through July. However, daylength appears
177
Edible Oilseeds, Grains, and Grain Legumes
to have a shortening effect on ower termination and maturity. It is difcult to compare the length of phases
between South Texas and West Texas because the amount of moisture is usually so different. However, in terms
of owering, the order between cultivars will remain the same, i.e., lines that ower rst in South Texas, ower
rst in West Texas. The same is generally true for ower termination, maturity, and drying. However, there are
some genotypes with a common ancestor that will stop owering earlier in West Texas and out of sequence.
Rain
As stated in most of the phases and stages, the amount of moisture has an effect on the length of time. The
ideal rain pattern is enough rain prior to planting the crop to ll the soil prole; a planting rain that will provide
enough moisture to plant; 30 days of dry weather (in a dry area so the root goes deep—not as important in a
wet area); rains about every week for the next 50 days, and then no rain until the crop is harvested. The rains
should be light enough so that the moisture percolates into the soil into the root zone. Continual rains saturate
the soil and keep oxygen out, yellowing the plants, and delaying the vegetative phase. The actual rain has the
following effects on the stages:
In the germination stage, a rain will often move the seed deeper in the soil, delaying emergence. In
certain types of soils, a rain can create a crust, delaying or preventing emergence. A rain will also
lower the temperature of the soil.
At the seedling stage, rain can splatter mud up on to the cotyledons and rst few leaves reducing the
photosynthetic surface and delaying growth. In some cases, a rain can cause erosion and cover seedlings
with mud. Once the cotyledons have inverted, the seedling has little push. If the seedlings are totally
covered, they will die. If part of the seedling is exposed, it can recover, but the stage will be delayed.
In the ripening phase, if there has been a drought, a rain can lead to regrowth which was discussed in
that phase.
In the drying phase, rain can reduce shatter resistance.
In 2000 in Oklahoma there was a period of rain, drizzle, rain, and overcast conditions that lasted over
3 weeks. With high temperatures a mold formed over all of the crops, gardens, and forests that ruined
the sesame, soybeans, sorghum, and cotton.
Rain can germinate seeds that were in dry soil at planting. The greater the difference between the initial
germination and this late germination, the greater the farming problems due to differing maturity dates.
In manual harvest, the ripe plants can be cut rst and the rest left for later cutting, but in combining, the
green plants will cause problems with moisture and seed quality.
Sesame plants suffer from standing water and will usually die if the water is on the stem for a period of
time. Excessive rain that leads to water logging in low spots can kill sesame in any phase.
In trying to predict production in an area it is more important to know the timing of the rains compared
to the phases than to know the total amount of rain.
Drought
As stated earlier sesame is drought tolerant, but as with every crop will do better with more moisture. In
US crops there is a weather phenomenon in the summer known as a “Texas high” when a high pressure area
sets up over Texas and southern Oklahoma. During this time it will not rain for about 6 weeks with the drought
starting sometime in June—coincident with the vegetative and reproductive phases. Even without this high
there is little rain during the summer (usually lower than 250 mm) during the growing phases. Sesame persists
in these conditions, and in extreme conditions, Amaranthus species have died while the sesame plants have
survived. The indeterminate nature of sesame allows it to bridge these drought periods.
In 2006 there was an extended drought throughout the US growing area resulting in virtually no subsoil
moisture prior to planting. In Uvalde there was only 70 mm of rain in 12 months through PM in an area that
averages 560 mm. There were no planting rains for the rainfed crops, and the only elds that performed close
to average were those where there were good pre-plant irrigations. Once the sesame germinated, there was a
dry line below the roots that prevented deep penetration. Trying to get the dry soil below wet, the irrigations
hurt the sesame more than they helped. Fields with fewer irrigations of around 25 mm per irrigation had higher
yields than elds with more irrigations of around 38 mm per irrigation.
178
Issues in New Crops and New Uses
Wind
In any breeding programs wind should be taken into account because of the potential of lodging. In the
last 10 years of the US sesame program through constant selective pressure, lodging has been a rare problem
that usually occurs only when winds exceed 60 km/h. In the 2006 northern Texas Sesaco nursery, less than 1%
of the plants lodged with two days of winds between 50 and 90 km/h.
During the germination stage, wind is rarely a problem except for hot continual winds that can pull
the moisture out of some soil types. If the farmer does not plant deep enough, the moisture around the
seed can evaporate and prevent germination. However, planting deeper to prevent this problem will
take the seedling longer to emerge.
In the seedling stage the wind can cover the seedlings with blowing dirt and sand. While seedlings
covered by rain carrying silt will seldom push through, the silt from wind is looser and occasionally, the
seedlings can push through and survive. Normally, the seedlings are low enough to have a low prole
to the wind and there is no lodging at this point. However, in windy areas such as northern Oklahoma
and Southern Kansas, the winds can whip the seedling around and the stems will form a cone into the
soil. There has been no apparent damage from this, and in fact, this may help the stem develop more
wind resistance.
In the vegetative phase in many areas of the West Texas where the soils are sandy, farmers need to
“sandght” on all of their crops. Rains create the problem in sandy soils by slicking the ground. Winds
can then carry sand that blasts the tender seedlings and depending on the intensity can just shred the
leaves and set the seedlings back or can “sandpaper” the plants to just stems. As soon as farmers can
get a tractor into the eld they will till the soil with an implement to trap the sand. Normally, one month
after planting, the plants are tall enough to not require sandghting.
During the reproductive phase, although it is rare, wind can blow a set of whole owers off the plant.
This tendency to blow off is genetic in terms of the strength of the pedicel.
Generally, the leaves act as shock absorbers and branches and plants rubbing against each other in the
wind, do not lose their capsules, but in the ripening phase as the plants lose their leaves, the capsules
come into contact, and the capsules can rub off. Triple capsules rub off more easily than single cap-
sules.
In the drying phase, the capsules will open and winds can cause the seed to shake out of the capsules.
Although the amount of shatter resistance is the largest determinant of the amount of seed lost, plant
architecture of the plant can make a difference. The tips of branches whip the most and are more apt
to lose seed.
Winds can be benecial in the drying phase in that they pull moisture out of the plants faster. Once
the plants are dry, the wind in conjunction with low humidity can increase the number of harvest hours
per day.
After the seedling stage, the main peril from wind is lodging. In understanding lodging, it is important
to realize that the stage and plant architecture can create different amounts of wind resistance. The
following characters present more resistance: tall plants, large leaves, branches, wide angle branches,
and three capsules per leaf axil. The weight of the plant also makes a difference once the winds start
bending the plants. Wet plants from rain tend to lodge more than dry plants.
There are three types of lodging: where the plants break at the stem, where the plants bend over but do
not break, and where the plants uproot and bend over. When a plant breaks over, it will rarely produce any
new seed, and the existing seed may or may not mature. If there is a total break, there is no hope, but if there
is still some active stem translocation through the break, there can be some yield recovery. The main causes
for uprooting of plants are shallow root systems and elds that have just been irrigated, creating a soft layer of
soil. When a plant bends over early in development, some lines adapt better than others in terms of having the
main stems turn up and continue owering. The tips of the branches are usually matted under the canopy and
will rarely turn up, but new branches can develop. As the plants go to drydown and the weight of the moisture
is lost, many of the bent plants will straighten up making the crop easier to combine.
179
Edible Oilseeds, Grains, and Grain Legumes
Temperature
The rule of thumb is that 150 frost free days are needed for sesame (Kinman and Martin 1954). Work has
been done in the greenhouse on optimum temperatures, but the conditions cannot approximate the interactions
between temperature, sunshine, and wind in the eld. Many publications have repeated that temperatures above
40°C affect fertilization and seed set (Weiss 1971) implying that sesame crops should not be grown in hot ar-
eas; however, excellent crops have been grown in Arizona where the day temperatures during the reproductive
phase are rarely below 40°C and often reach 50°C. In Yuma in 2006, there was a three day period when the
temperatures were never below 43°C at dawn at a nursery with thousands of lines, and the capsules set seed.
However, the temperatures around the owers may have been cooler from air movement, evaporation of water
from the soil, and transpiration from the plants.
On the cold side, as stated earlier low temperatures can prevent or inhibit germination; will lead to slower
growth; and will slow down ripening. In the US there can be frosts at the end of the cycle. Planting on time will
normally keep the crop from frosts through the full maturity stage, but after that point, frosts are possible and
are an advantage. Frosts can accelerate the drying phase, which moves harvest into a better weather window.
In learning the latest time to plant, there were many commercial elds that had a frost or even a hard freeze.
In the 1950s a crop in Kansas had a hard freeze near maturity and the plants dried down quickly. The seed was
harvested and appeared to be ne; however, within a week the seed was rancid. M. Kinman (pers. commun.)
watched the harvest, tested the seed, and found extremely high acid values. He speculated that the freeze cre-
ated ice within the seed. The temperatures and length of time below freezing were not recorded. Since that
time, there have been several hard freezes around minus 5°C for as much as 6 hours during the drying phase.
There was an accelerated drydown, but the harvested seed was not damaged. However, there has not been a
freeze when the seed contains high moisture (60% at physiological maturity). Dry seed placed in the freezer
for weeks have germinated.
The effects of frost are difcult to determine because conditions vary too much to compare frosts. In
general, a frost may accelerate a drydown, and it appears that at the same temperatures, crops further along on
drying will be affected more than crops that are still green. In one extreme case, a line from Paraguay that was
still owering continued owering after a frost that dried down the other 1,100 lines that were still green.
In 1998 there was an extreme abnormal frost that hit Oklahoma and north Texas in mid September—seven
weeks before normal early frosts. Most of the elds were still owering, but there were no general patterns—
some elds stopped owering and others continued owering. One interesting effect was that in most elds the
leaves on the side of the wind dried down. This was a repeat of the observation in a late planted eld in 1990
where the temperatures were above freezing, but below freezing with the wind chill factor.
Hail
The sesame growing areas in the US are prone to hail storms. As with any crop, if the hail is severe, it
can destroy the crop. However, the present US cultivars of sesame have good recovery traits. There is sesame
germplasm that will not branch under any circumstance including losing the growing tip on the main stem.
This type of germplasm has been eliminated from the US program because of the problems with hail. Within
branching lines there are differences in the amount of branching in terms of the number of branches and the
percentage production of seed on the branches. Branches are important in hail damage because the growing
shoot of the main stem is tender and a direct hit will often break the tip off. Unless branches start, the produc-
tion of that particular plant is stopped at the point of the hail strike.
The effect of hail on the phenology depends on development stage of the plant. In the vegetative phase the
hail may lengthen the phase as much as a week, whereas in the later phases it will shorten the phase. Given a
hail of equal intensity, the earlier the damage, the higher probability of recovering from the damage.
In the seedling stage, if there are no rst leaves and the head of the seedling is severed, the plant will
die. If the rst true leaves are severed, the plants will form branches from where the cotyledons meet
the stem. Above the rst set of leaves there will be branches commensurate with the amount of light
and the number of node pairs available to form branches.
180
Issues in New Crops and New Uses
In the rest of the vegetative and early reproductive phase, in moderate to high populations, the dominant
plants will get the hail hits and damage, and often the minor plants will grow through the canopy and
become the dominant plants. If the hail hits the primary meristem, the optimum situation is to have it
break off entirely. Often the top is broken over and hangs on the plants. The tip will bend up and will
ower and set capsules, but with the reduced ow of nutrients there will not be much seed produced.
However, the worst effect is that the primary meristem appears to suppress the secondary meristems
and these plants will not have substantial branches. In some years, the severity of the damage is not seen
until harvest when there is lower yield. In extreme cases, the leaves have been torn apart, but the plants
have gone on to branch and produce owers and capsules, but the reproductive phase is delayed.
Sesame leaves are soft and hail will easily go through leaving minor holes. A single hail stone can
damage multiple leaves. If there are enough hail stones, the hail can reduce the leaf surface area. Hail
hitting the stems will leave “bruises”—darkened areas.
In the reproductive phase, hail can damage the leaves enough to reduce the rate of owering but will
actually extend the date to ower termination. However, if the leaves are severely shredded, the plants
may stop owering. Although the stem and capsules are green, they do not produce enough photosyn-
thesis to ll the seeds. The plants will delay going to physiological maturity.
In the ripening phase, there are fewer leaves and the capsules are more exposed. The hail can have a
direct hit on a capsule and open it taking it to drydown ahead of capsules below it. The hit can break
the capsule down, but it will often stay attached to the plant and dry down. A severe hail will denude
stems of the capsules and may break off parts of the main stems or branches.
In the drying phase, dry capsules are open and have a brittle attachment to the stem. Direct hits can
detach the capsule or shatter out the seed.
Salinity
Sesame is more sensitive to salt than most crops including cotton and alfalfa. At some point the salinity
will prevent germination, but this subject has not been studied sufciently. Salinity slows down growth and
makes the plants more yellow. In Arizona there were irrigated elds where the sesame would thrive near the
head of the ditch but would not grow near the tailwater. In these areas, the water was from the Colorado River,
which was fairly salty. In 1987, different lines were planted in 8 row strips in a eld where cotton and alfalfa
would not grow in the west fth of the eld due to salinity. There was as much as 30 meters difference in how
far out into the salty area some sesame lines would grow indicating genetic variability.
Effects of Weather Perils
The paragraphs above detail many of the perils from weather, but sesame withstands weather very well.
The Risk Management Agency of the US Department of Agriculture funded a study of sesame, which provided
the information shown in Table 17 (Anon 2004a). The author provided the raw data for the study.
As can be seen sesame is a survivor crop even in modern agriculture as it has been over the past 5,000
years in subsistence farming in many areas of the world.
REFERENCES
Angus, J.F., R.B. Cuningham, M.W. Moncur, and D.H. Mackenzie. 1980. Phasic development in eld crops I.
Thermal response in the seedling phase. Field Crops Res. 3:365–378.
Anon. 2004a. Research report on hybrid sunower, sesame, and spelt crop insurance programs. p. 1–96. Watts
and Associates, Billings, MT.
Anon. 2004b. Descriptors for sesame. Int. Plant Genetic Res. Inst., Rome, Italy.
Ashri, A. 1985. Sesame improvement by large scale cultivars intercrossing and by crosses with indehiscent and
determinate lines. p. 177–181. In: A. Ashri (ed.), Sesame and safower status and potentials. FAO Plant
Production and Protection Paper 66, Rome, Italy.
Ashri, A. 2007. Sesame (Sesamum indicum L.). p. 231–289. In R.J. Singh, (ed.), Genetic resources, chromo-
some engineering, and crop improvement. Vol 4. Oilseed crops. CRC Press, Boca Raton, FL.
181
Edible Oilseeds, Grains, and Grain Legumes
Avila M., J.M. 1999. Cultivo del ajonjoli, Sesamum indicum L. Fondo Nacional de Investigaciones Agropec-
uarias, Maracay, Venezuela.
Bar-tel, B. and Z. Goldberg. 1985. Descriptors for sesame: A modied approach. p. 191–197. In: A. Ashri (ed.),
Sesame and safower status and potentials. FAO Plant Production & Protection Paper 66. Rome, Italy.
Beech, D.F. 1985. Sesame: Research possibilities for yield improvement. p. 96–106. In: A. Ashri (ed.), Sesame
and safower status and potentials. FAO Plant Production and Protection Paper 66. Rome, Italy.
Beech, D.F. 1995. Australian sesame industry: An overview. p. 19–33. In: M.R. Bennett and I.M. Wood (eds.),
Proc. First Australian Sesame Workshop, Darwin – Katherine, 21–23 March 1995.
Bennett, M., D. L’Estrange, and G. Routley. 1997. Sesame research report, 1996–1997 wet season. Katherine,
Australia.
Bennett, M. 1998. Sesame seed. The new rural industries, a handbook for farmers and investors. www.ridc.
gov.au/pub/handbook/sesame.html.
Culp, T. 1960. Inheritance of papershell capsules, capsule number, and plant color in sesame. J. Hered.
51(3):101–103.
Day, J.S., D.R. Langham, and W. Wongyai. 2002. Potential selection criteria for the development of high-
yielding determinate sesame cultivars. p. 29–35. Sesame and Safower Newsletter, Inst. Sustainable
Agr., Cordoba, Spain.
Hiltebrandt, V.M. 1932. Sesame (Sesamum indicum L). Bul. Appl. Bot. Genet. Plant Breed. 9:109–114.
Joshi, A.B. 1961. Sesamum. The Indian Central Oilseeds Committee, New Delhi, India. p. 109.
Table 17. Weather perils affecting sesame (1987–2003).
Peril Distribution Frequency Extreme Stage(s) affected
Crop lost (%)
Typical year Extreme year
Drought Localized Most years 2000–2002 Any 1-5 30 affected
but not lost
Prevented planting
(due to lack of
rain on non-
irrigated crops
Localized Most years 1996, 1997 Germination <1 to 3 15–25
Excessive heat General Annually All stages 0
Heavy rain
(at planting)
Scattered Annually Germination,
seedling
1–3 5
Excessive rains
(causing lakes)
Localized Annually 1989, 2003 Any <1 3
Rain at harvest General Most years 2000 All of the drying
phase
0-5 30 in 2000
onlyz
Unseasonably cold Localized Some years 1998 Late bloom <1 2–4
Frost Localized Annually 1998 Late bloom 1–2 15 affected
but not lost
Hail Isolated Annually 2003 Any, more af-
fected the
later the stage
<1 2
Wind Scattered Annually Before juvenile <1 1–2
Scattered Annually After juvenile <1 1–3
Localized Annually 2003 Drying <1 1–3
zIn 2000 there was a period of 3 weeks with heavy dews, fogs, cloud cover, and little sunshine. All of the crops,
gardens, lawns, and forests developed a fungus that covered the vegetation. Up until that point the sesame and
other crops were harvested, but after that point all crops were abandoned. Oklahoma State extension personnel
said that there had been no previous record of this phenomenon, and it has not repeated.
182
Issues in New Crops and New Uses
Kang, C.W. 1985. Studies on owering, capsule bearing habit and maturity by different plant types in sesame.
Ph.D. Thesis Korea Univ., Suweon.
Kang, C.W., J.I. Lee, and E.R. Son. 1985. Studies on the owering and maturity in sesame (Sesamum indicum
L.) III. Growth of capsule and grain by different plant types. Korean J. Crop Sci. 30(2):158–164.
Kinman, M.L. 1955. Sesame production. Texas Agr. Expt. Sta. Bul., College Station.
Kinman, M.L. and J.A. Martin. 1954. Present status of sesame breeding in the United States. Agron. J.
46(1):2 2 27.
Kobayashi, T. 1981. The type classication of cultivated sesame based on genetic characters. p. 86–89. In: A.
Ashri (ed.), Sesame: Status and improvement, proceedings of expert consultation. FAO Plant Production &
Protection Paper 29. Rome, Italy, 8–12 Dec. 1980.
Langham, D.G. 1944. Natural and controlled pollination in sesame. J. Hered. 35:254–256.
Langham, D.G. 1945. Genetics of sesame. J. Hered. 36:245–253.
Langham, D.G. and M. Rodriguez. 1945. El ajonjoli (Sesamum indicum L.): Su cultivo, explotacion, y mejoramiento.
Bol. 2, Publ. Ministerio de Agricultura y Cria, Maracay, Venezuela.
Langham, D.G. 1946. Genetics of sesame III: “Open sesame” and mottled leaf. J. Hered. 37:149–152.
Langham, D.G., M. Rodriguez, and E. Reveron. 1956. Dehiscencia, y otras caracteristicas del ajonjoli Sesamum
indicum, L., en relacion con el problema de la cosecha. Genesa, Publ. Tecnica 1, Maracay, Venezuela.
Langham, D.R. 2000. Method for making non-dehiscent sesame. United States patent 6,100,452.
Langham, D.R. 2001. Shatter resistance in sesame. p. 51–61. In: L. Van Zanten (ed.), Sesame improvements
by induced mutations. Proc. Final FAO/IAEA Co-ord. Res. Mtng, IAEA, Vienna, TECDOC-1195.
Langham, D.R. and T. Wiemers. 2002. Progress in mechanizing sesame in the US through breeding. p. 157–173.
In: J. Janick and A. Whipkey (eds.), Trends in new crops and new uses. ASHS Press, Alexandria, VA.
Langham, D.R. 2004a. Non-dehiscent sesame variety S25. United States patent 6,781,031.
Langham, D.R. 2004b. Non-dehiscent sesame variety S26. United States patent 6,815,576.
Langham, D.R. 2006a. Non-dehiscent sesame variety S28. United States patent 7,148,403.
Langham, D.R. 2006b. Non-dehiscent sesame variety Sesaco 29. United States patent application
2006/0230472.
Langham, D.R., G. Smith, T. Wiemers, and J. Riney. 2006. Southwest sesame grower’s pamphlet. Sesaco
Corporation, San Antonio, Texas.
Lee, J.I. 1986. Sesame breeding and agronomy in Korea. Crop Expt. Sta., Rural Development Administration,
Suweon, Korea.
Mazzani, B. 1962. Mejoramiento del Ajonjoli en Venezuela. Ministerio de Agricultura y Cria, Centro de
Investigaciones Agronomicas, Maracay, Venezuela, Monographia 3.
Mazzani, B. 1999. Investigacion y tecnologia del cultivo del ajonjoli en Venezuela. Ediciones del Consejo
Nacional de Investigaciones Cienticos y Tecnologicas (CONICIT), Caracas, Venezuela.
Mulkey Jr., J.R., H.J. Drawe, and R.E. Elledge, Jr. 1987. Planting date effects on plant growth and development
in sesame. Agron. J. 79:701–703.
Sapin, V., G. Mills, D. Schmidt, and P. O’Shanesy. 2000. Growing sesame in South Burnett. Department of
Primary Industries, Queensland Government. www.dpi.qld.gov.au/eldcrops/2888.html.
Sarker, A.M. 2004. Effect of honeybee pollination on the yield of rapeseed, mustard and sesame. Geobios-
(Jodhpur) 31(1):49–51.
Suddhiyam, P., S. Chatcharoenthong, and S. Kritjanarat. 2001. Seed development of red seeded sesame cultivar
Ubon Ratchathani. In: W. Wongyai (ed.), Proc. Second Natl. Conf. Sesame, Sunower, Castor, and Saf-
ower, Nakhon Nayok, Thailand, 16–17 August 2001.
Triangtrong, A. 1984. The effect of environmental factors on growth, development, and yield of sesame (Sesa-
mum indicum L.) in south-eastern Queensland. Master thesis, Univ. Queensland, Brisbane, Australia.
Weiss, E.A. 1971. Castor, sesame and safower. Leonard Hill Books, London. p. 311–525.
Weiss, E.A. 2000. Oilseed crops. 2nd ed. Blackwell Science., Malden, MA
Yermanos, D.M. 1980. Sesame. p. 549–563. In: H. Fehr and H. Hadley (eds.), Hybridization of crop plants.
Agronomy-Crop Science Society of America, Madison, WI.
... However, sesame is yet to become a major crop in the world because of the weak productivity, the lack of improved varieties with tolerance to biotic and abiotic stresses . Sesame is mainly grown in arid and semi-arid areas and is often challenged by severe drought (Langham 2007). Although sesame is rated as a relatively drought tolerant crop, the plant growth and yield are critically affected under prolonged stress (Sun et al. 2010;Dossa et al. 2017b). ...
Article
Full-text available
An increasing number of candidate genes related to abiotic stress tolerance are being discovered and proposed to improve the existing cultivars of the high oil-bearing crop sesame (Sesamum indicum L.). However, the in planta functional validation of these genes is remarkably lacking. In this study, we cloned a novel sesame R2-R3 MYB gene SiMYB75 which is strongly induced by drought, sodium chloride (NaCl), abscisic acid (ABA) and mannitol. SiMYB75 is expressed in various sesame tissues, especially in root and its protein is predicted to be located in the nucleus. Ectopic over-expression of SiMYB75 in Arabidopsis notably promoted root growth and improved plant tolerance to drought, NaCl and mannitol treatments. Furthermore, SiMYB75 over-expressing lines accumulated higher content of ABA than wild-type plants under stresses and also increased sensitivity to ABA. Physiological analyses revealed that SiMYB75 confers abiotic stress tolerance by promoting stomatal closure to reduce water loss; inducing a strong reactive oxygen species scavenging activity to alleviate cell damage and apoptosis; and also, up-regulating the expression levels of various stress-marker genes in the ABA-dependent pathways. Our data suggested that SiMYB75 positively modulates drought, salt and osmotic stresses responses through ABA-mediated pathways. Thus, SiMYB75 could be a promising candidate gene for the improvement of abiotic stress tolerance in crop species including sesame.
... There are four phases in the phenology of sesame: vegetative, reproductive, ripening, and drying and there is a tremendous amount of variability in these phases [19]. Sesame is an indeterminate species, and thus, there is an overlap between the reproductive, ripening, and drying phases [18]. ...
Chapter
Full-text available
Harvest aids are traditionally used to desiccate weeds to improve crop quality and harvest efficiency. Field studies were conducted in Texas to determine the effect of harvest aids (glyphosate, diquat-dibromide, glufosinate-ammonium, and carfentrazone-ethyl) on sesame drydown and yield. The objective was to identify one or more harvest aids that could (1) accelerate drydown, (2) burn-down green weeds, (3) even up a field with varying levels of drydown, (4) stop regrowth, (5) stop vivipary, and (6) prepare to plant a new crop. Other than diquat-dibromide, the herbicides were chosen based on the effect on weeds in other crops. The plan was to apply the herbicides 1 week before physiological maturity (PM), at PM, and 1 week after PM. However, sesame maturity is very sensitive to ground moisture, ambient temperature, and relative humidity. The weather was different in all trials and some stages could not be completed. In two cases, the trials had to be abandoned; however, certain patterns emerged. All the herbicides accelerated drydown compared to the untreated check. Diquat-dibromide and glufosinate-ammonium dried sesame faster than glyphosate and carfentrazone-ethyl. The higher rates of the herbicide dried down the sesame faster than the low rate. Although there were some differences in yields across the three application periods, there was no consistent pattern.
Article
Full-text available
The impact of ground addition of potassium humate and boron spraying on sesame indicators, yield, and its components was investigated in a field experiment at the Research Station of the Field Crops Department of the College of Agriculture - Tikrit University 2021. The experiment was carried out using a randomized complete block design (RCBD) using a factorial experiment consisting of two components, the first of which was the addition of potassium humate and the second of which was the spraying of boron. During the first week of June 2021, seeds were planted in soil that had been amended with potassium humate at five different concentrations: 0, 3.6, 7.2, 10.8, and 14.4 g.l ⁻¹ . A randomized full block design was used to statistically assess the data gathered from spraying three different amounts of boron (0, 100, and 200) g.l ⁻¹ prior to the onset of flowering. Here is a rundown of the findings: The number of capsules per plant treated with potassium humate (H3) was the highest (89.111 capsule.plant ⁻¹ ), and the total yield was also much higher (compared to other treatments) (3.427 kg.ha ⁻¹ ). Both the capsule length (2.573 cm) and the individual yield (15.673 g) were significantly higher in plants that were subjected to a boron (B3) spraying treatment. For the features of the number of seeds per capsule (71,333 seeds.capsule ⁻¹ ) and the weight of one thousand seeds, the interaction combination (H5B3) yielded the greatest significant value (4.491 g).
Article
Full-text available
Introduction: Sesame is an important cash crop that can be grown with limited resources. In recent decades it has drawn interests of many researchers and developers. This study analyzed the economics of Sesame (Sesamum indicum L.) produced in northern region of the Republic of Benin. Methods: Structured questionnaire was used to gather primary data from 120 farmers who made up the sample size and were chosen using a multistage sampling technique. Data were analyzed using descriptive statistics, profitability analytical tools, multiple regression analysis and Likert scale rating technique. Profitability analytical tools were used to assess the economic performance of the sesame production; a multiple regression model was used to analyze factors that determine the output of the production in the study area; a 5-point Likert scale rating technique was utilized to rank the production’s challenges according to farmers’ observations. Results: The findings revealed that sesame ismainly produced in sole cropping system and in rotation with other crops. The net farm income analysis showed that sesame farming was a profitable venture in the study area. The study also showed that factors like age, household size, crop rotation, and capital input influence the revenue of sesame production. While age, household size and capital input have a beneficial and significant influence on the farms’ net revenue from sesame produce, crop rotation has a negative effect on it. Amongst the various constraints identified, themost significant ones are access to labor and land, uneven ripening, lack of storage facilities and access to improved seed. Discussion: Based on these results, authorities in agricultural sector should develop and promote this value chain at the national level as it will greatly boost the country’s economy.
Article
Full-text available
Climate change is shifting agricultural production, which could impact the economic and cultural contexts of the oilseed industry, including sesame. Environmental threats (biotic and abiotic stresses) affect sesame production and thus yield (especially oil content). However, few studies have investigated the genetic enhancement, quality improvement, or the underlying mechanisms of stress tolerance in sesame. This study reveals the challenges faced by farmers/researchers growing sesame crops and the potential genetic and genomic resources for addressing the threats, including: (1) developing sesame varieties that tolerate phyllody, root rot disease, and waterlogging; (2) investigating beneficial agro-morphological traits, such as determinate growth, prostrate habit, and delayed response to seed shattering; (3) using wild relatives of sesame for wide hybridization; and (4) advancing existing strategies to maintain sesame production under changing climatic conditions. Future research programs need to add technologies and develop the best research strategies for economic and sustainable development.
Article
Precise knowledge on the impact of varying soil moisture and nutrient levels on the root system architecture of sesame is lacking. To that end, four non-dehiscent sesame cultivars (Sesaco32, 35, 38 and 40) were grown in rhizoboxes under four different soil water levels (60, 80, 100 and 120% of soil water holding capacity) over four replications. Two identical runs were performed without added nutrients and two other runs with added nutrients. The rhizoboxes were scanned at 2, 4, 7, 9, 11, 13, 14, 16, 18, and 21 days after planting (DAP) without nutrients, and only until 16 DAP with added nutrients. Images were analyzed for total root length (TRL) and average length per individual root branch (ARL). Results showed that without nutrients, TRL reached a plateau at 50.5 cm at 18 DAP on average across treatments, and S35 had the highest (66.4 cm) and S40 the lowest (31.4 cm) TRL at 21 DAP. TRL was only marginally affected by soil water level without nutrients. With added nutrients, TRL showed an exponential growth pattern reaching 103 cm at 16 DAP on average across treatments and was not affected by cultivar nor soil water level. These results showed that reduced soil water level has little to no impact on TRL, but that genotypic differences play an important role in determining belowground development without nutrients. A visual representation of root spatial distribution showed that although TRL differences existed between cultivar without nutrients, root spatial exploration appeared consistent. With added nutrients, the lack of significant difference in TRL between 100 and 120% soil water level (100.2 ± 19.2 and 114.1 ± 19.7 cm respectively) was not consistent with root spatial exploration, as these two soil water treatments displayed different RSA. These results show that sesame's early rooting behavior is controlled closely by genotypic factors in nutrient poor conditions, and that soil fertility can have a strong positive impact on early root growth. This is of interest to sesame breeders who could use nutrient poor environments to select for root architecture traits and improve the drought tolerance of the crop.
Article
Full-text available
Genetic dissection of yield components and seed mineral-nutrient is crucial for understanding plant physiological and biochemical processes and alleviate nutrient malnutrition. Sesame (Sesamum indicum L.) is an orphan crop that harbors rich allelic repertoire for seed mineral-nutrients. Here, we harness this wide diversity to study the genetic architecture of yield components and seed mineral-nutrients using a core-collection of worldwide genotypes and segregating mapping population. We also tested the association between these traits and the effect of seed nutrients concentration on their bio-accessibility. Wide genetic diversity for yield components and seed mineral-nutrients was found among the core-collection. A high-density linkage map consisting of 19,309 markers was constructed and used for genetic mapping of 84 QTL associated with yield components and 50 QTL for seed minerals. To the best of our knowledge, this is the first report on mineral-nutrients QTL in sesame. Genomic regions with a cluster of overlapping QTL for several morphological and nutritional traits were identified and considered as genomic hotspots. Candidate gene analysis revealed potential functional associations between QTL and corresponding genes, which offers unique opportunities for synchronous improvement of mineral-nutrients. Our findings shed-light on the genetic architecture of yield components, seed mineral-nutrients and their inter-and intra-relationships, which may facilitate future breeding efforts to develop bio-fortified sesame cultivars.
Article
Full-text available
Irrigation decision support systems (DSS) are tools that can help achieve higher system level water use efficiency by more accurately targeting water application to crop need. They also have a role to play in preventing over-irrigation of drought tolerant crops that can be sensitive to flooded conditions. However, there are challenges in developing DSS for newly introduced crops in regions where they have not typically been produced. One such crop is sesame, a recently introduced drought tolerant crop in the southeastern United States where up to 50% of the agronomic crop production is irrigated. A first irrigation DSS, called SesameFARM1, was developed in 2013 by estimating a water demand curve using the Food and Agricultural Organization (FAO) crop coefficient (Kc) values, seasonal measures of the leaf area index (LAI) for the crop measured in 2012, and an estimated maximum rooting depth. On a daily time-step, SesameFARM1 estimated crop evapotranspiration using the product of the Kc and the ETo obtained from a local weather station, and an estimation of the maximum plant available water based on the available water capacity for the soil type and the maximum crop rooting depth. To improve SesameFARM1, LAI data from 6 years of field trials along with root data from a previous study were used to develop a breakpoint regression model for LAI and total functional root length. In SesameFARM2, the resulting curve for LAI was used to estimated continuous Kc values; and total measured functional root length replaced the estimation of maximum rooting depth in a new variable called root water access. SesameFARM2 performance was compared to SesameFARM1 using 6 years of weather data from Citra FL. SesameFARM2 consistently recommended less water be applied, and recommendations of water application during the senescence phase of the crop were reduced. Because of sesame’s inherent drought tolerance, a more conservative irrigation recommendation is likely more appropriate. Therefore, SesameFARM2 is likely a better model than SesameFARM1 and may help growers unfamiliar with sesame achieve irrigation higher irrigation crop water productivity.
Article
Full-text available
Current determinate sesame lines yield poorly because they have fewer capsule-bearing nodes than indeterminate varieties. Unlike soybean varieties, sesame varieties are unable to compensate for fewer capsule-bearing nodes by increasing the number of capsules per inflorescence. Based on our observations, potential selection criteria for the development of high-yielding determinate sesame varieties include: short seed maturation period; high harvest index of the capsule zone; and high yield. Seed maturation period should be used rather than the flowering period to amplify the difference between period required for seed development at the lower-most and uppermost nodes. New sesame varieties developed using these criteria may have more uniform seed maturity and greater productivity without any reduction in yield.
Conference Paper
Full-text available
In the 1996 FAO/IAEA meetings in Turkey, many presentations reported improved shatter resistance from mutation breeding. Yet, in looking at the pictures it was difficult to discern the relative amount of shatter resistance between breeding programs. At the time, we were using a subjective rating. The question was whether we could develop an objective methodology. The results of the first efforts were reported at the 1998 FAO/IAE meetings in Thailand in a paper titled ‘Quantification of shatter resistance in sesame’. The paper included photos of capsules from 139 genotypes ranging from 0 to 100% shatter resistance. In the conference proceedings, the paper was shortened as ‘Shatter resistance in sesame’ and included ideas generated at the conference. Amram Ashri suggested another paper that would include more information about mechanization of sesame, which became ‘Progress in mechanizing sesame in the US through breeding’. The methodology reported was very time consuming and so a new methodology was developed and presented in a patent ‘Method for making non-dehiscent sesame, United States patent 6,100,452’. As shatter resistance improved there was a modification presented three patents ‘Non-dehiscent sesame, United States patent 8,080,707’, ‘Method for breeding improved non-dehiscent sesame. United States patent 8,581,028 B2’, and ‘Method for mechanical harvesting of improved non-dehiscent sesame. United States patent 8,656,692”. These last 3 patents have the same description, but the claims are different. The new methodology is still time consuming, but capsules can be harvested from physiological maturity through complete drydown, and still provide relative shatter resistance. Wasana Wongyai modified the methodology a bit, but the important part is not so much to be able to compare genotypes from breeding programs across the world, but to determine relative shatter resistance within a breeding program. All 7 papers are included in ResearchGate.
Patent
Full-text available
In the 1996 FAO/IAEA meetings in Turkey, many presentations reported improved shatter resistance from mutation breeding. Yet, in looking at the pictures it was difficult to discern the relative amount of shatter resistance between breeding programs. At the time, we were using a subjective rating. The question was whether we could develop an objective methodology. The results of the first efforts were reported at the 1998 FAO/IAE meetings in Thailand in a paper titled ‘Quantification of shatter resistance in sesame’. The paper included photos of capsules from 139 genotypes ranging from 0 to 100% shatter resistance. In the conference proceedings, the paper was shortened as ‘Shatter resistance in sesame’ and included ideas generated at the conference. Amram Ashri suggested another paper that would include more information about mechanization of sesame, which became ‘Progress in mechanizing sesame in the US through breeding’. The methodology reported was very time consuming and so a new methodology was developed and presented in a patent ‘Method for making non-dehiscent sesame, United States patent 6,100,452’. As shatter resistance improved there was a modification presented three patents ‘Non-dehiscent sesame, United States patent 8,080,707’, ‘Method for breeding improved non-dehiscent sesame. United States patent 8,581,028 B2’, and ‘Method for mechanical harvesting of improved non-dehiscent sesame. United States patent 8,656,692”. These last 3 patents have the same description, but the claims are different. The new methodology is still time consuming, but capsules can be harvested from physiological maturity through complete drydown, and still provide relative shatter resistance. Wasana Wongyai modified the methodology a bit, but the important part is not so much to be able to compare genotypes from breeding programs across the world, but to determine relative shatter resistance within a breeding program. All 7 papers are included in ResearchGate.
Patent
Full-text available
Non-dehiscent sesame (Sesamum indicum L.) (IND) designated Sesaco 36 (S36) is herein disclosed. Its degree of shatter resistance, or seed retention, makes S36 suitable for mechanized harvesting and for selection for sesame crop growth in most geographical locations, particularly where whiteflies are a high risk factor. In addition, S36 sesame produces a larger, heavier seed than previously described varieties.
Article
Full-text available
Gene action for yield and its attributing traits was studied in the F 1,s and F 2's of a 10 × 10 half diallel in sesame. The analysis of genetic components revealed that both additive (D) and non-additive (H) type of gene actions were involved in the inheritance of most of the traits studied with preponderance of non-additive gene actions for all the characters in both the F 1, and F 2 generations. It was also supported by estimates of s 2g/ s 2s ratios. Further, dominance ratio (H 1/D) 1/2 indicated the presence of over dominance for all the traits in both the generations except days to maturity, which was partial and complete dominance in F 1 and F 2 generations, respectively. Asymmetrical distribution of positive and negative genes and unequal frequency of dominant and recessive genes in the parents were observed for most of the traits. The estimates of narrow sense heritability were low in most of the traits. It was high for days to maturity in both the generations and moderate for number of effective branches per plant and number of seeds per capsule in F 2 generation.