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Europ. J. Agronomy 24 (2006) 236–246
Variation in pod production and abortion among chickpea
cultivars under terminal drought
L. Leporta,1, Neil C. Turnera,b,∗, S.L. Daviesa,c, K.H.M. Siddiquea
aCentre for Legumes in Mediterranean Agriculture, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
bCSIRO Plant Industry, Private Bag No. 5, Wembley, WA 6913, Australia
cWestern Australian Department of Agriculture, PO Box 110, Geraldton, WA 6531, Australia
Received 12 October 2004; received in revised form 5 July 2005; accepted 2 August 2005
Abstract
The effect of terminal drought on the dry matter production, seed yield and its components including pod production and pod abortion was
investigated in chickpea (Cicer arietinum L.). Two desi (with small, angular and dark brown seeds) and two kabuli (with large, rounded and light
coloured seeds) chickpea cultivars differing in seed size were grown in a controlled-temperature greenhouse, and water stress was applied by
withholding irrigation 1 (early podding water stress, ES), 2 (mid-podding water stress, MS) or 3 (late-podding water stress, LS) weeks after the
commencement of pod set. In addition, the pod and seed growth of well-watered plants was followed for the first 19 days after pod set. Growth
of the pod wall followed a sigmoid pattern and was faster in the desi than in the kabuli cultivars, while no difference was found in early seed
growth among genotypes. Time of pod set affected the yield components in all treatments with the late-initiated pods being smaller, having fewer
seeds per pod and smaller seeds, but no significant difference between pods initiated on the same day on the primary and secondary branches was
observed. Early stress affected biomass and seed yield more severely than the later stresses, and in all stress treatments secondary branches were
more affected than primary ones. Pod production was more affected by early stress than by late stress, regardless of cultivar. Pod abortion was more
severe in the kabuli than in the desi cultivars, but final seed size per se did not appear to be a determinant of pod abortion under terminal drought
conditions. The data indicated that the production and viability of pods was affected as soon as water deficits began to develop. The results show
that pod abortion is one of the key traits impacting on seed yield in chickpeas exposed to terminal drought and that irrespective of differences in
phenology, kabuli types have greater pod abortion than desi types when water deficits develop shortly after first pod set.
Crown Copyright © 2005 Published by Elsevier B.V. All rights reserved.
Keywords: Cicer arietinum L.; Seed growth; Pod growth; Water relations; Pod abortion; Seed abortion; Kabuli and desi chickpea
1. Introduction
There are two types of chickpea (Cicer arietinum L.): (i)
the small-seeded desi chickpea with a dark and thick seed coat,
that is split and the kernel used for dahl or flour primarily in
SouthAsia,and(ii)the large-seeded kabulichickpeawithalight-
colouredand thin seedcoat that is usedas a whole seedor in hom-
mus or falafal primarily in countries around the Mediterranean
Basin. While disease, especially Ascochyta blight (Ascochyta
rabiei;Mycosphaerella rabiei;Didymella rabiei), is currently
a major limitation to chickpea production in Mediterranean-
∗Corresponding author. Tel.: +61 8 6488 4723; fax: +61 8 6488 1140.
E-mail address: ncturner@clima.uwa.edu.au (N.C. Turner).
1Present address: Osmoadaptation and Stress Metabolism, UMR CNRS 6026
ICM, University of Rennes 1, F-35042 Rennes Cedex, France.
climatic regions (Cubero, 1984; Knights and Siddique, 2002),
abiotic stress, particularly terminal drought, is also a major con-
straint to yield in most regions (Singh et al., 1990; Subbarao
et al., 1995; Thomson et al., 1997; Leport et al., 1998, 1999;
Siddique et al., 1993, 2000; Turner, 2003). The development
of disease resistant cultivars and disease management packages
willagain highlight the sensitivityof chickpea to abiotic stresses.
In the absence of disease, a field study with five desi geno-
types and one kabuli genotype showed that total above-ground
biomass did not differ among genotypes, but seed yields of rain-
fed chickpeas subjected to terminal drought were reduced from
53 to 42% compared to those of irrigated plants in all geno-
types (Leport et al., 1999). This was related to a decrease in
pod numbers from 44 to 30% and a decrease in seed number
from 46 to 35% (Leport et al., 1999), but whether this was due
to a reduced production or increased abortion of pods was not
investigated.Asubsequentgreenhouse study with one cultivarof
1161-0301/$ – see front matter. Crown Copyright © 2005 Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.eja.2005.08.005
L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246 237
chickpea showed that both the production and abortion of pods
was reduced by a water deficit imposed after the commencement
of pod set (Behboudian et al., 2001). The study by Leport et al.
(1999) suggested that in addition to pod production or abortion,
seed yields of chickpeas decreased because of fewer seeds per
pod in some genotypes, suggesting that seed abortion can also
occur. Under field conditions Davies et al. (1999) showed that
terminal drought reduced the duration of seed filling, and hence
the final seed size, in three chickpea genotypes. However, seed
size under both rainfed and irrigated conditions was similar in
both the secondary and primary branches (Davies et al., 1999).
Recent studies by Ma et al. (2001) and Furbank et al. (2004)
have shown that the pod is an important photosynthetic organ
in refixing respired carbon within the pod wall that is then
translocated to the developing seed. As the seed coat of the
developing seed is unaffected by water deficits in the rest of
the plant (Shackel and Turner, 2000), the refixation of car-
bon within the pod is considered to be even more important
under terminal drought (Ma et al., 2001). The ability of the
pod and seed to survive when drought occurs is an important
step in improving yield under terminal drought. Under termi-
nal drought conditions, kabuli types of chickpea have a greater
reduction in yield and pod number per plant compared to desi
types(Leport et al., 1999; Siddique et al., 1999), butit is not clear
whetherthis is associated with their generallylater flowering and
hence exposure to greater terminal stress, their greater seed size,
or other inherent genetic differences between desi and kabuli
types.
The present study was initiated to determine whether there
was any variation in pod and seed production and abortion
among chickpea cultivars. By imposing water deficit treatments
at three stages during reproductive development, we aimed to
determine the stage at which a water deficit induced pod abor-
tion. Differences in pod initiation among the cultivars in the
greenhouse were small and the water deficit treatments were
commenced at the same time after pod set in each cultivar. As
previous studies have shown that pod numbers are lower in kab-
uli than in desi genotypes (Leport et al., 1999; Siddique et al.,
1999), we compared pod abortion in both small- and medium-
seededdesi cultivarsand small- andlarge-seeded kabulicultivars
(the small-seeded kabuli cultivar had the same seed size as the
medium-sized desi cultivar) to determine whether seed size per
se had an influence on pod abortion.
2. Materials and methods
2.1. Experimental design
Four chickpea (C. arietinum L.) cultivars differing in seed
size, two desi types, cv. Tyson (mean seed size = 0.12g seed−1),
cv. Sona (0.22g seed−1), and two kabuli types, cv. Kaniva
(0.42gseed−1),and cv.Narayen (0.20 g seed−1) weregrown in a
controlled-temperature greenhouse, set at 22 ◦C/15◦C day/night
temperatures, at CSIRO, Floreat Park, Perth, Western Australia
(31◦57S, 115◦47E). The plants were grown in free-draining
pots, each made from 425 mm long, 150 mm diameter polyvinyl
chloride tube, and filled with 12.4kg of sieved, fine-textured
loam (Calcic Haploxeralf) from the top 10cm of a field in
Merredin (Thomson et al., 1997) mixed with 1.4kg of coarse
sand. One gram of a commercial microelement preparation
(Richgrow®), 7.5g of potassium nitrate, 7.1 g of ammonium
nitrate, 10.7g of calcium nitrate and 7.6g of triple superphos-
phate was mixed with each 50kg of soil, corresponding to 1.4 g
of N, 0.6g of P and 0.8g of K per pot.
2.2. Management
The plants were sown on 30 June (the usual season for plant-
ing chickpeas in the southern hemisphere) in a commercial
potting mix in flat trays. All seeds were inoculated with a com-
mercial Group N Bradyrhizobium immediately before sowing.
Three days after sowing (DAS) one seedling was transferred into
each pot previously watered to field capacity. All pots were irri-
gated commencing 3 DAS with 200ml of water per pot every
second day to maintain the soil near field capacity. For each
genotype, pots were designated to one of the four groups cor-
responding to four treatments: well-watered control (C), early
podding water stress (ES), mid-podding water stress (MS), and
late-podding water stress (LS). Control plants were irrigated
every 2 days until the ES plants reached maturity (121DAS
for Tyson, Sona, and Kaniva and 128DAS for Narayen). Irri-
gation of Tyson, Sona and Kaniva was maintained until 93,
100, and 107DAS for ES, MS and LS, respectively, before
the irrigation was stopped. As Narayen began podding 1 week
later than the other cultivars, irrigation was maintained until
100, 107 and 114DAS for ES, MS and LS, respectively, and
then the irrigation was stopped. For each genotype, 28 pots
were used, seven per treatment; four pots for the measure-
ment of pod production, abortion and seed yield, and three
were used for the measurement of leaf water potential as the
sampling of leaves for leaf water potential can affect leaf area
and branch development. Three pots in the control treatment
were also used for the measurement of early pod and seed
growth. The 112 pots were randomized on benches in four
replicate blocks and the benches moved within the greenhouse
weekly to minimise any variation in light and temperature on the
plants.
2.3. Podding date
For each plant in each treatment and cultivar, the start and end
of podding was recorded. Every second day from the beginning
until the end of pod set, each new visible pod (about 2 mm long)
on the plants used for the pod production studies was tagged and
its podding date recorded. Similarly, the new pods on the three
well-watered control plants for the measurement of early pod
and seed growth were tagged in Tyson, Sona and Kaniva for the
first 15 days and in Narayen for the first 19 days after pod set
(DAPS).
2.4. Leaf water potential
Using the pressure chamber technique as described pre-
viously (Leport et al., 1998) and following the precautions
238 L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246
described by Turner (1988), the leaf water potential (Ψl)of
upper (unshaded) fully expanded leaves was measured around
midday (1030–1430h) on clear sunny days (photosynthetically
active radiation above 1700mol m−2s−1) at 3- to 4-day inter-
vals from when water was withheld to 23 days after irrigation
was terminated. The measurements were performed on main
stem or lateral branches (no differences were observed when
direct comparisons were made) for each cultivar and treatment
on the three pots not used for pod production and abortion mea-
surements.
2.5. Pod and seed growth
Forthe early pod and seed growthstudy,all the pods were har-
vested at 15DAPS for Tyson, Sona and Kaniva and at 19DAPS
for Narayen and dried to constant weight in a forced-draught
ovenat70◦C. For each cultivar, all pods with same date of pod
set were combined and partitioned into pod walls and seeds for
counting and weighing.
2.6. Pod production, abortion and dry matter partitioning
When the plants reached maturity, they were harvested at
soil level and individually partitioned into primary and sec-
ondary branches. Primary branches were defined as the largest
stems growing near the base, which included the mainstem
and the branches growing from the lowest three nodes of
the mainstem. The secondary branches grew from nodes 3–5,
9–12, 12–15 and 7–10 of the primary branches in Tyson,
Sona, Kaniva and Narayen, respectively. Each primary and
secondary branch was dried separately to constant weight
in a forced-draught oven at 70◦C and then partitioned into
leaves, stems, and individual pods. Leaflets that had shed at
the time of harvest were not included in the total above-
ground biomass. Each pod was partitioned into pod wall and
seeds. All the samples were weighed and the number of seeds
determined.
The tagged pods were put into four categories: (i) tags where
a pod was no longer present, (ii) small pods with small or no
seed, (iii) large pods with no seed, and (iv) large pods with one
or more seeds. While (i) represents the pods that were shed,
(ii) and (iii) represent infertile pods, and (iv) represent fertile
pods. For the purposes of this paper, pod abortion refers to both
infertile and shed pods (the sum of (i)–(iii)), while seed abor-
tion refers to the reduction in the number of seeds within a pod
containing more than one seed. Seeds less than 40% of the aver-
age size for any one genotype were considered to be aborted
seed.
2.7. Seed yield and yield components
Seed yield and yield components were determined for each
cultivar and treatment from the dry weight measurements
described above. The harvest index at maturity was calculated
from the ratio of seed dry weight (non-aborted) to total above-
ground plant dry weight. The number of fertile and infertile pods
perplant,the number of non-aborted seeds per plant and per pod,
theseed weight per plant and the average seed size (weight) were
calculated.
2.8. Statistical analysis
The data were analysed as a randomized complete block
design using Genstat 6.1 (©Lawes Agricultural Trust, Rotham-
sted Experimental Station, 2003). Where means and standard
errors are presented, they were calculated with Microsoft Excel
2000 (©Micrsosoft Corp., 1985). Regressions were fitted using
SigmaPlot 8.0 (©SPSS Inc., 2002).
3. Results
3.1. Phenology, and pod and seed development
Pod set commenced 10 days after flowering at 82, 85, 87 and
98DAS for Sona, Kaniva, Tyson and Narayen, respectively. In
the well-watered plants (controls), podding ended 114DAS in
Sona and Kaniva, 117DAS in Tyson and 126DAS in Narayen.
The plants in the ES, MS, and LS treatments finished podding
11, 9 and 2 days earlier on average than in the respective well-
watered controls.
The growth of the pod wall, as measured by dry weight,
occurred earlier than the seed (data not presented). Pod wall dry
weight followed a sigmoid growth pattern and reached a maxi-
mum at 9–13DAPS in the two desi cultivars, Tyson and Sona,
and about 17–19DAPS in the two kabuli cultivars, Kaniva and
Narayen(data notpresented).Early meanseed dry weightdid not
differ among genotypes and was only0.012 ±0.001gat 9 DAPS
when the mean pod wall weights varied from 0.035 ±0.002g in
Tyson to0.094±0.005gin Kaniva. Rapid seed dry weight accu-
mulation did not commence in all four cultivars until 13DAPS
when the pod walls were near their final dry weight (data not
presented).
Atmaturity,the pod wall weight per pod,seed weight per pod,
seeds per pod and seed size decreased acropetally from the first-
formed basal pods to the later-formed pods near the tip of the
branches in each of the adequately watered chickpea genotypes,
except in Kaniva in which the number of seeds per pod on the
primary branches was not significantly greater than 1 seed per
pod (Fig. 1a and b). A similar decrease was observed in the
chickpeas subjected to the stress treatments (data not shown).
Provided the pods were initiated on the same day, regression
analysis showed that there were no significant differences in
seed and pod characteristics among pods on the primary and
secondary branches (Fig. 1a and b).
The average seed size (weight/seed) in the well-watered
plants at maturity varied across cultivars in the same order as
in the seeds used at sowing (Fig. 2). The small-seeded kab-
uli cultivar, Narayen, was similar in size to the medium-sized
desi cultivar (Fig. 2b and d). In the kabuli cultivars, Kaniva and
Narayen, about 35–40% of the pods had no seeds compared to 5
and 15% in Tyson and Sona, respectively (Fig. 2e). Although
the individual seed sizes varied markedly in all four culti-
vars, the majority of the seeds were within ±50% of the mean
(Fig. 2e).
L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246 239
3.2. Development of water deficits
During podding, the midday leaf water potential in the
well-watered plants on clear sunny days was about −1.0MPa
in all four cultivars (Table 1). As the plants were grow-
ing rapidly at the time of the imposition of the water stress
treatments, the rate of development of the water deficit was
slower in the ES treatment as the plants were smaller than
in the MS and LS treatments when the plants were larger
(Table 1). With the imposition of the ES treatment, the mid-
day leaf water potential decreased at 0.17MPa day−1from
3 to 4 days after the stress was imposed in the two desi
cultivars compared to a decrease of 0.19–0.28MPa day−1in
the two kabuli cultivars (Table 1). In the MS and LS treat-
ments, the midday leaf water potential began to decrease
2–5 days after the imposition of the stress treatment and
decreased at a rate of 0.4–0.5MPaday−1in all four cultivars
(Table 1).
3.3. Effect of terminal stress on biomass, seed yield and its
components
The total above-ground biomass and seed yield produced by
the four genotypes in the well-watered controls by maturity was
similar at 42–48 and 20–24gplant−1, respectively (Fig. 3a and
b). For each treatment and genotype, there was an average of
four primary branches per plant. The primary branches (without
their leaves) represented an average of 30% of the above-ground
vegetative dry matter, while the secondary branches represented
an average of 8% of the above-ground vegetative dry matter.
Whensubjected to water stress,both total biomass and seedyield
decreased to a greater extent the earlier the stress was imposed.
However, the seed yield decreased more than the biomass with
the stress treatments, so that the harvest index also decreased
linearly with the duration of water stress in all four genotypes
(Fig. 3e). The harvest index was lower in the well-watered
Narayen than the other cultivars, while the two kabuli cultivars,
Fig. 1. (a) The seed weight per pod (䊉,), pod wall weight per pod (,) and (b) seed number per pod (,) and seed size (,♦) for pods set on the primary
(closed symbols) and secondary (open symbols) branches at different dates after first pod set (from the first-formed basal pods to the later-formed pods near the tip
of the branches) in four chickpea genotypes in the well-watered control treatment. The lines are the fitted linear regressions for the primary (unbroken line) and
secondary (dashed line) branches.
240 L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246
Fig. 1. (Continued).
Kaniva and Narayen, were more severely affected by the longer
periods of stress than the desi cultivars, so that in the ES treat-
ment the seed yield and harvest index in the two kabuli cultivars
were significantly lower than in the two desi cultivars (Fig. 3b
and e).
All cultivars had more than one seed per pod on average. In
the well-watered plants, the number of pods with more than
one seed was 4% in Kaniva, 21% in Narayen and 37% in
the two desi cultivars (Fig. 3c). The stress treatments did not
significantly affect the number of seeds per pod in the two
desi cultivars, but the ES treatment reduced the seed num-
ber to a single seed per pod in the two kabuli chickpeas. The
stress treatments had a much smaller effect on seed size (28%
reduction in the ES treatment on average) than on seed yield
(90% reduction in ES treatment on average). Although seed
size was not reduced by the LS treatment, the mean seed size
was significantly reduced in the ES treatment in all cultivars
(Fig. 3d).
3.4. Effects of terminal stress on seed production by the
primary and secondary branches
In the well-watered plants, pods set on the same date had
the same seed characteristics whether the seed was produced on
the primary or secondary branches (Fig. 1). However, stress had
a major impact on the productivity of the secondary branches.
In Tyson, the imposition of the terminal stress at the beginning
of podding (ES) reduced the number of pods on the secondary
branches by 89% compared to a reduction of only 38% on the
primary branches, and reduced the seed yield of the secondary
branches by 99% compared to 66% in the primary branches
(Table 2). In the other cultivars the ES treatment had also a
greater effect on the secondary compared to primary branches.
However in Sona, seed abortion on the secondary branches was
less and the seed yield was reduced less by the ES treatment than
in the other three cultivars (Table 2). In addition while there was
a decrease in average seed size on the secondary branches in
L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246 241
Fig. 2. The frequency distribution of the number of seeds per plant (a–d) and proportion of seeds (e) as a proportion of the average seed size in four genotypes of
chickpea, (a) Tyson, (b) Sona, (c) Kaniva and (d) Narayen in the well-watered control treatment. The average seed size for each genotype is given.
all of the genotypes, the differences among the cultivars in seed
size observed on the primary branches were not observed in the
seeds on the secondary branches (Table 2).
3.5. Pod development under stress
The stress treatments affected both the production and abor-
tion of pods. The ES treatment had the major effect on the
number of pods at maturity in all genotypes (Fig. 4). Compared
to the well-watered controls, the total number of pods per plant
in the ES treatment was reduced by 66–75%. The later stress
treatments, particularly the LS treatment, had less of an effect
on pod production (Fig. 4). Fig. 4 also shows that after the stress
treatments were imposed pod numbers began to decrease below
thosein the well-watered plants about 5 days after the imposition
of the stress. This coincides with the time that the midday leaf
water potential first began to decrease below that in the controls
in all the stress treatments and genotypes (Table 1).
242 L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246
Table 1
The time to the start and the rate of decrease of leaf water potential (Ψl) after
water was withheld in the three stress treatments (early, middle and late termi-
nation of watering) and four chickpea genotypes
Stress Time to start (days after
water withheld) Rate of decrease in
Ψl(MPaday−1)
Tyson (−1.01MPa)
Early 3.3 0.17
Middle 3.9 0.45
Late 4.6 0.39
Sona (−1.02MPa)
Early 4.2 0.17
Middle 2.1 0.46
Late 3.6 0.45
Kaniva (−1.03MPa)
Early 2.9 0.28
Middle 1.9 0.48
Late 3.9 0.43
Narayen (−0.94MPa)
Early 4.3 0.19
Middle 3.4 0.45
Late 4.1 0.50
The mean value of the leaf water potential in the control plants of the four
cultivars is given in parenthesis.
Even in the well-watered chickpeas, 10–23% of the pods on
the primary branches were aborted (Table 3). On the secondary
branches the abortion was greater, particularly in the two kabuli
cultivars, Narayen and Kaniva, even in the well-watered plants.
Theimposition of water stress increasedpod abortion to between
28 and 48% on the primary branches and between 55 and 82%
on the secondary branches in the desi cultivars (Table 3). Pod
abortion was significantly greater (P<0.001) in the two kabuli
cultivars than the two desi cultivars independent of seed size and
was significantly greater (P< 0.001) in all three stress treatments
than in the well-watered controls (Table 3).
4. Discussion
Chickpea is an indeterminate annual cool-season grain
legume that produces its seeds progressively (acropetally)
along the branches. In water-limited Mediterranean and sub-
tropical environments, the plants are usually subjected to ter-
minal drought unless irrigated. In a greenhouse experiment,
Behboudian et al. (2001) showed that a water deficit imposed
Table 3
The percentage of the total pod number that had aborted at maturity on the
primary and secondary branches in four chickpea genotypes given four stress
treatments: well-watered control, early (ES), middle (MS) and late (LS) termi-
nation of irrigation
Pod abortion (% of total pod number)
Control ES MS LS
Primary
Tyson 10.5 27.6 29.8 33.7
Sona 14.6 41.3 48.3 42.5
Kaniva 23.0 64.0 66.1 47.2
Narayen 17.7 71.0 56.0 59.5
Secondary
Tyson 12.3 82.5 71.2 54.6
Sona 17.3 53.1 70.7 58.5
Kaniva 39.2 99.0 92.4 74.5
Narayen 26.4 86.2 79.6 79.3
LSD (P<0.05) = 13.6.
from the beginning of podding reduced pod numbers in the culti-
var Sona by reducing both the production of pods and increasing
pod abortion. The present study has shown that the timing of the
imposition of terminal drought has a major impact on both the
production and abortion of pods and hence on seed yield, and
that the response varies depending on whether the chickpea is a
desi or kabuli type. Moreover, seed size per se does not appear
to have an influence on pod production or abortion.
Previous field studies have shown that in a Mediterranean-
type environment water deficits develop near the onset of pod-
ding (Leport et al., 1998, 1999), induce faster and shorter seed
filling (Davies et al., 1999), reduce pod and seed number, and
reduce seed yield and seed size (Davies et al., 1999; Leport et
al., 1999). Under terminal drought conditions, kabuli types of
chickpea have a greater reduction in yield and pod numbers per
plant compared to desi types (Leport et al., 1999; Siddique et
al., 1999). This may be associated with their later flowering and
podding than the desi types (Leport et al., 1999) and therefore
greatervulnerability to decreasing soil moisture. However,in the
present study, the water deficits were imposed at the same time
after first pod set in both types of chickpea and the kabuli types
still had greater reductions in yield and pod number than the
two desi types when the stress was imposed from early podding.
On average, terminal water stress increased pod abortion 50%
in the desi cultivars and 75% in the kabuli cultivars. This com-
Table 2
The seed yield and pod number per plant as a percentage of the well-watered controls and the seed number per pod and average seed size of primary (first) and
secondary (second) branches in four chickpea genotypes in the early stress treatment
Seed yield (% of control) Pods plant−1(% of control) Seeds pod−1Average seed size (g)
First Second First Second First Second First Second
Tyson 34.1 1.1 61.9 10.7 1.51 1.00 0.093 0.072
Sona 27.2 10.5 45.6 24.6 1.67 1.43 0.135 0.120
Kaniva 10.3 0.3 39.0 27.5 1.00 1.00 0.244 0.101
Narayen 4.5 2.9 30.0 22.7 1.00 1.00 0.113 0.096
LSD (P<0.05) 5.4 6.6 12.5 ns 0.25 0.33 0.80 ns
L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246 243
Fig. 3. The relationship between (a) total above-ground biomass (excluding shed leaves) per plant, (b) seed yield per plant, (c) seed number per pod, (d) seed size,
and (e) harvest index, and the time that the plants were without irrigation in four chickpea genotypes, Tyson (䊉), Sona (), Kaniva () and Narayen (). Values are
means±one standard error of the mean (n= 4).
pares with 35% of pods being aborted in a desi genotype in the
field at a low rainfall site that received on average about 210 mm
of growing-season rainfall (Siddique and Sedgley, 1986). In the
present controlled-environment study, higher rates of pod abor-
tion as a result of water stress were expected because the initial
number of pods set in the greenhouse was not reduced by the
low temperatures that hinder pod set in the field (Croser et al.,
2003). Moreover, the rate of development of the water stress was
more rapid in the greenhouse than in the field, even though the
minimum leaf water potential (−3.0 MPa) in both environments
was similar (Leport et al., 1998). However, what was of note
in the present study was the much greater effect of the water
deficits on pod abortion on the secondary branches compared
to the primary branches, particularly in the two kabuli cultivars
in which pod abortion on the secondary branches was between
74 and 99%. While the final seed and pod characteristics of the
surviving pods on the primary and secondary branches set on
the same day were similar (Fig. 1), the delay in pod set on the
secondary branches clearly had a big influence on the survival of
those pods under terminal drought. This suggests that the devel-
244 L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246
Fig. 4. Cumulative pod number after first pod set in four genotypes of chickpea given four water stress treatments: C, well-watered control; ES, early stress; MS,
middle stress; and LS, late stress. The arrows denote the time that the stress treatments were imposed. The mean ±one standard error of the mean (n=4) is given for
the final pod numbers only.
opment of early flowering kabuli genotypes may not give the
same benefit to yield as the development of early desi genotypes
for water-limited environments (Berger et al., 2004), unless the
initiation and development of pods on the secondary branches
can also be enhanced. Moreover, it suggests that if supplemen-
tary irrigation is available, this should be used as a preference
on kabuli chickpea which are more susceptible to water deficits
and respond better to supplemental irrigation than desi types and
that irrigation at flowering and early podding when chickpea
is most sensitive to water deficits (Khanna-Chopra and Sinha,
1987) will be much more beneficial than irrigation later in pod
development.
Seed size per se does not appear to be a major factor affecting
pod abortion. Pod abortion was high in both kabuli types that
differed in seed size, but much lower in Sona than in Narayen,
despite their similarity in seed size. At the time that the midday
water potential began to decrease below that in the well-watered
controls, seed development was minimal and seed size was sim-
ilar in all four cultivars and there was no difference in pod-wall
dry weight between Sona and Narayen. Thus, the rate of growth
of the pod or seed during early seed growth was not consid-
ered to be a factor that affected the different degrees of pod
abortion. The desi cultivar Sona was selected for its high yield,
and early and high pod production in Mediterranean-type envi-
ronments (Siddique and Khan, 2000). The present study has
shown that with terminal water stress this cultivar had lower
pod and seed abortion and better maintenance of seed size
on the secondary branches than the kabuli cultivars, suggest-
ing that selection for earlier pod set, particularly on secondary
branches, can lead to higher yields under terminal drought. The
desi gene pool is considered older, and hence closer to the wild
progenitor, Cicer reticulatum, than the kabuli chickpea that is
regarded as a more recent evolutionary branch of the cultigen
(Ladizinsky, 1995). Thus, it is likely that genetic variation for
at least some characters is narrower in the more-recent kabuli
types than in the desi types (Abbo et al., 2003). Our observations
are consistent with those of Liu et al. (2003) who compared the
pod abortion of kabuli and desi chickpea subjected to crowd-
L. Leport et al. / Europ. J. Agronomy 24 (2006) 236–246 245
ing and concluded that kabuli types of chickpea are inferior to
desi types in their morphological plasticity. Therefore, we sug-
gest that, irrespective of seed size, there was a greater abortion
of pods by the kabuli than desi cultivars in response to water
shortage as a result of the more-recent evolutionary history and
smaller selection pressure for drought resistance among kabuli
types.
The development of stress in the four cultivars was very
similar (Table 1). In all cases the reduction of pod production
occurred at the same time as the decrease in midday water poten-
tialwas first detected and well before the leaf water potential was
likely to have reduced the rate of leaf photosynthesis (Leport et
al., 1999; Ma et al., 2001). Previous studies have shown that
the pod water potential is higher than the leaf water potential
(Leport et al., 1999) and that the turgor pressure of the seed coat
is unaffected by a decrease in the water potential of the pods
and leaves (Shackel and Turner, 2000). This suggests that the
growth of the pod and seed was not reduced as a consequence
of the water potential or turgor pressure of those organs, nor
from a lack of assimilates, but that pod and seed production and
abortion was possibly affected by root signals (Emery et al.,
1998).
As chickpea is indeterminate, the branches continue to
develop, flower and set pods and seeds while water is avail-
able and temperatures are neither too cold (Croser et al., 2003)
nor too hot. This study has shown that the seed dry weight, seeds
per pod and seed size decrease in the late-set pods compared to
the early set pods. However, this appears to be a function of the
time of pod set and not a function of whether the pods are pro-
duced on the primary or secondary branches. Thus there does
not appear to be a hierarchy of pod or branch order for assimi-
lates. This may be because the major source of carbohydrates for
the developing seed appears to be the subtending leaf, at least in
well-watered chickpea (Singh and Pandey, 1980), and because
the pod actively recycles respired carbon within the pod itself
(Ma et al., 2001; Furbank et al., 2004). It does mean that when
sampling pods, age not position on the branches is important for
valid comparisons.
5. Conclusions
This study has shown that the kabuli chickpea cultivars were
more susceptible to terminal water stress than desi chickpea
cultivars and that this was not related to seed size or differ-
ences in phenology. Further while there was a reduction in
both total biomass and pod production under the stress condi-
tions imposed, pod abortion, particularly of pods on secondary
branches, had the major effect on seed yield. The difference
among cultivars in pod abortion was not driven by the size of
the seed or pod at the time that the water stress was imposed
or by final seed size, but was inherently greater in the kabuli
than the desi cultivars. Moreover, the study suggests that pod
water relations were not responsible for the differences among
cultivars in pod abortion. Our results also suggest that where
supplemental irrigation is available, preference should be given
to growing kabuli types that benefit more from irrigation and a
higher value in the market place.
Acknowledgements
We thank Mike Barr, Rebecca Carpenter and Christiane Lud-
wig for assistance with the measurements of dry weight and
data processing. We also thank Drs. Patrizia Gremigni, Jairo
Palta, Jens Berger, Shahal Abbo and Peter Hocking for their
comments on the manuscript. This research was supported by
CSIRO, the Centre for Legumes in Mediterranean Agriculture
at the University of Western Australia, and the Grains Research
and Development Corporation of Australia.
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