Coffee Peaberry as a Potential Seed Source for Production

Abstract

Coffee pea berry is a unique feature of coffee seed as the result of the berry producing a single bean instead of the normal two during fertilization at the field. This might happen due to three major factors i.e. failure in one of the two ovules in the ovary to be fertilized and set seed, failure in the further development of the endosperm and incompatibility of the two parents during pollination. Different coffee seed sources, types and stages were evaluated and compared with pea berries for germination and seedling growth and field performance of seedlings produced from pea berries. For most Ethiopian known coffee varieties, the potential occurrence of pea berry was also recorded for two consecutive seasons at the Jimma National Coffee Research Center with the objectives to evaluate coffee pea berry as a potential seed source and see variability among Arabica coffee varieties in terms of producing pea berries. The relevant data were statistically analyzed and treatments means were compared using SAS software. The results depicted that there was no significant variations between pea berries and normal bean with regard to germination, emergence and subsequent growth of the seedlings and yield potential yield performance under field conditions. Significant variations were observed among pre-sowing seed treatments for the parameters considered at early stage. Likewise, the coffee varieties were found to significantly differ in producing pea berry proportion with a mean value of 7% for pure lines and 16% for hybrid variety. In general, the hybrid coffee variety showed two fold higher than the pure line coffee varieties. Pea berry may not be predominantly a heritable character, because seeds produced from coffee trees raised from pea berries will not develop all in to pea berries.

Full text

International Journal of Research Studies in Science, Engineering and Technology
Volume 7, Issue 9, 2020, PP 30-35
ISSN 2349-476X
International Journal of Research Studies in Science, Engineering and Technology V7 ● I9 ● 2020 30
Coffee Peaberry as A Potential Seed Source for Production
Alemseged Yilma1 and Taye Kufa2
1Ethiopian Institute of Agricultural Research, Jimma Agricultural Research Center
2 IITA-Burundi Station, Bujumbura
*Corresponding Author: Alemseged Yilma, Ethiopian Institute of Agricultural Research, Jimma
Agricultural Research Center
INTRODUCTION
In coffee, seed production is typically
characterized by growth /phonological/ stage
from flowering up to fruit development.
Anthesis in Arabica coffee can occur on a single
day or during a few days, with one or more
flowerings within a single reproductive period
(Wormer, 1964; Alvim, 1973). Each flowering
period lasts only 2 or 3 days and is followed by
intense vegetative development.
High seed quality is essential for optimum stand
establishment in coffee. As a result, it is
necessary to have seed physical, germination
percent, physiological and health tests that
permit rapid, objective and accurate evaluation
of seed quality. Coffee beans are classified as
dicotyldon and usually flat on one side and
transverse on the other. But sometimes coffee
bear a single bean in its pod and this single bean
is called pea berry. Normally, the fruit
("cherry") of the coffee plant contains two seeds
("beans") that develop with flattened facing
sides, but sometimes only one of the two seeds
is fertilized, and the single seed develops with
nothing to flatten it.
Pea berries beans are round and oblong in shape
and tend to be larger and denser. A Pea berry in
coffee is the result of the berry producing a
single bean instead of the normal two. It
is caused by two major factors;
1. Failure of one of the two ovules in the ovary
to be fertilized and set seed, and
2. Failure in the development of the endosperm.
These two conditions give the remaining seed a
chance to have enough space inside the coffee to
develop in to roundish shape with good
endosperm development. Failure of fertilization
or endosperm development in one of the ovules
can be caused by various factors (Srinivasan and
Vishveshwara, 1980). These are;
1. Unfavorable weather condition that cause
flower abortion (environmental conditions)
ABSTRACT
Coffee pea berry is a unique feature of coffee seed as the result of the berry producing a single bean instead
of the normal two during fertilization at the field. This might happen due to three major factors i.e. failure
in one of the two ovules in the ovary to be fertilized and set seed, failure in the further development of the
endosperm and incompatibility of the two parents during pollination. Different coffee seed sources, types
and stages were evaluated and compared with pea berries for germination and seedling growth and field
performance of seedlings produced from pea berries. For most Ethiopian known coffee varieties, the
potential occurrence of pea berry was also recorded for two consecutive seasons at the Jimma National
Coffee Research Center with the objectives to evaluate coffee pea berry as a potential seed source and see
variability among Arabica coffee varieties in terms of producing pea berries. The relevant data were
statistically analyzed and treatments means were compared using SAS software. The results depicted that
there was no significant variations between pea berries and normal bean with regard to germination,
emergence and subsequent growth of the seedlings and yield potential yield performance under field
conditions. Significant variations were observed among pre-sowing seed treatments for the parameters
considered at early stage. Likewise, the coffee varieties were found to significantly differ in producing pea
berry proportion with a mean value of 7% for pure lines and 16% for hybrid variety. In general, the hybrid
coffee variety showed two fold higher than the pure line coffee varieties. Pea berry may not be
predominantly a heritable character, because seeds produced from coffee trees raised from pea berries will
not develop all in to pea berries.
Keywords: Arabica coffee, pea berry, growth, Yield

Coffee Peaberry as A Potential Seed Source for Production
31 International Journal of Research Studies in Science, Engineering and Technology V7 ● I9 ● 2020
2. Insufficient pollination due to failure of the
agents of pollination (e.g. insect, wind),
3. Incompatibility of the two parents during
pollination, a common case in inter-specific
hybrids (e.g. Arabusta, a hybrid between
Arabica and Robusta species), and
4. Probably genetic defects.
Coffea Arabica of the mono sperm variety has a
strong tendency to produce pea berries. This is
also the case for coffee hybrids where the
tendency is even more marked. The presence of
pea berry is considered to be a defect in coffee
production and used as a criterion in coffee
breeding. An increase of 1% of pea berry beans
in a crop reduces production by 0.75
%(Wintgens, J.N. (2004).
Pea berries are very rare fruit, only making up
5-7% of an entire harvest of coffee beans from
any plantation. On the other hand, abnormalities
in coffee seed occur as elephant beans,
polyspermy beans, and empty beans. To roast
more evenly, because their rounder shape
minimizes sharp edges and allows the berries to
roll about the roasting chamber more easily, as
well as because the alleged higher bean density
may improve heat transfer in the roasting
process. However, some source claim that these
effects are minor, and that the major benefit of
peaberry beans is that they have been carefully
selected, which is essential for optimal quality,
regardless of bean shape (Kenneth Davids,
2003).
In Ethiopia, there is no any formal system
responsible for the production and supply of
improved coffee seeds from the released and
adaptable coffee varieties (Taye et al., 2011).
The Jimma agricultural research center /JARC/
is the only governmental institution that had
taken the initiative of multiplying improved
coffee seeds of the nationally released coffee
berry disease (CBD) resistant varieties since
1987 and distributed a total of 789230kg of
improved coffee seeds which have been
produced over the last three decades (1989-
2017) and disseminated (Paulos, 2008; Taye et
al., 2011)to all over the major coffee growing
areas of the country(JARC,2017)
In Ethiopia, during coffee seed preparation pea
berries seed are sort out and discard and unused
as a seed to raise seedlings at nursery.
Analytical purity test done by Melkam A. et al.
(2014), that laboratory analysis also identifies
and quantifies impurities (pea berry, cracked,
shriveled and others) that may occur in a seed
lot. Therefore, testing pea berries seeds for
germination, emergence and grow as good
seedling and consequently the bearing nature is
very important. This study was undertaken with
the specific objectives to evaluate the potential
use of pea berry as seed source in coffee
production and proportion of pea berry
development in arabica coffee varieties.
MATERIAL AND METHODS
The trial was conducted at the Jimma
agricultural research in south western Ethiopia
geographically located 7° 7’ N and 36° E. It is
situated within the Tepid to cool humid
highlands agro-ecological zone of the country at
an altitude range of 1753 meters above sea level.
The areas receives high amount of rainfall with
a long-term mean total of 1573.6 mm per
annum, which is distributed into 166 days. The
driest months usually last between November
and February. The mean maximum and
minimum air temperatures are 26.3 and 11.6 °C,
respectively (JARC, 2017-old and update this
weather data)
The experiment was run from November 2016
up to December 2019. Different growth nature
types of coffee seed and processing stage i.e.
clean coffee, normal parchment coffee; fresh
cherry, partial dry cherry, green berry and
parchment pea berry were prepared and
evaluated for the germination, emergence and
early growth performance at nursery stage
according to Tesfaye et al., 2006. Coffee
seedlings performance also evaluated in non
destructive and destructive measurement as
compare pea berry to other seed source. The pea
berry seed source seedlings also transplanted
and evaluated for yield at the field. Besides, few
Ethiopian coffee varieties were also evaluated
for pea berry proportion for two harvesting
seasons.
RESULT AND DISCUSSION
After two months of sowing, clean coffee
(parchment removed) had a higher emergence
percentage and followed by pea berry seed.
Starting from 60th days after sowing (DAS),
there was a significant difference of emergence
percentage among different coffee seed source,
except clean coffee and pea berry seed. At 90
and 105 days, still the pea berry seed emergence
increase with no significant difference between
clean coffee, fresh cherry, parchment and partial
dry cherry(Table1). Initially the pea berry
emergency percentage was delayed from clean

Coffee Peaberry as A Potential Seed Source for Production
International Journal of Research Studies in Science, Engineering and Technology V7 ● I9 ● 2020 32
coffee because of longer imbibitions period that
may be required since the seed is hard enough to
soak because of its well developed endosperm.
Regarding germination and subsequent
emergence, since the embryo development is
unaffected, pea berries also can germinate and
produce seedlings as of the normal seed in this
study.
Table1. Mean emergence (%) of coffee seedlings due to seed types and days after sowing (DAS).
Seed type
Days after sowing (DAS)
60
75
90
105
Fresh cherry
13d
37.04 bc
66.67a
75.92b
Partial dry cherry
10e
18.52c
59.26ab
79.63ab
Green berry
11.16de
14.81 c
38.89b
62.96c
Clean coffee
40.66a
70.37 a
81.49a
87.04a
Pea berry parchment
20.33b
53.70ab
75.93a
81.48ab
Normal parchment
16.50c
38.89 bc
64.81ab
79.62ab
S.E
0.9467
8.26
8,23
5.14
C.V (%)
8.81
36.79
22.11
11.44
Means followed by same letter(s) are not significantly different at P≤ 0.05 probability level
The Growth Stage
The growth stage of different seeds source are
vary, where clean coffee, parchment, pea berry
and partial dry cherry were had fastest growth
than fresh cherry and green berry. Clean coffee
attains early to first true leaf than others at 120
days of after transplanting (Fig. 1.). At 135
DAS, the clean coffee, parchment, pea berry and
fresh cherry showed better performance of
growth stage than others accordingly.
Fig1. Effect of coffee seed source on growth stage at 120 days
The least first pairs of true leaf growth and high
percentage of solider growth stage at 120 and
135 days (Figs1 and 2) were recorded from
green berry seed, indicating the much delayed
rate of growth in coffee seedlings.
At 135 days, two pairs of leaves observed in
higher percentage accordingly on clean coffee,
pea berry, parchment, fresh cherry, partial dry
cherry and green berry in that order.

Coffee Peaberry as A Potential Seed Source for Production
33 International Journal of Research Studies in Science, Engineering and Technology V7 ● I9 ● 2020
Fig2. Effect of coffee seed source on growth stage at 135 days
Growth Parameters
Except number of node, there was a significant
difference in most of the growth parameters
which include the plant height, girth, internodes
length, leaf number and area. In all parameters
clean coffee and pea berry perform better than
the other, and the least growth recorded in all
parameters in green berry (Table 2.). As far as
the root growth parameters no significant
difference were obtained among all seed source
(Table 3.).
Table2. Effect of seed type on the early growth of coffee seedlings
Seed type
Growth parameters
Plant ht
(cm)
Girth
(cm)
Number of
node
Inter node
length (cm)
Leaf number
Leaf area (cm)
Fresh cherry
32.84b
4.61c
10.25
3.20c
9.58cd
558.07cd
Partial dry cherry
36.34ab
5.12bc
9.92
3.40bc
23.0bcd
655.43bcd
Green berry
25.52c
4.09c
9.58
2.48d
16.0d
455.95d
Clean coffee
40.25a
6.41a
10.0
4.05ab
33.83a
964.13a
Pea berry
39.33a
5.94ab
9.5
4.26a
31.67ab
902.12ab
Parchment
36.71ab
5.97ab
9.83
3.83abc
27.67abc
788.42abc
S.E
1.82
0.32
0.49
0.21
3.11
8.91
C.V (%)
8.97
10.29
8.74
10.29
21.37
21.37
Means followed by same letter(s) are not significantly different at P≤ 0.05 probability level
Destructive Parameters
Like Taye and Alemseged (2007) works, clean
coffee seed was performed better than the
parchment coffee in all destructive parameters
recorded.
Similar result was found on leaf, shoot and root
destructive parameters, where clean coffee stood
first in all parameters and followed by pea berry
and parchment resulted significantly higher than
the other seed source as the growth parameters.
The least dry matter production was obtained in
all parameters from the seed source of fresh
cherry and green berry.
Though, there is a significant difference in seed
source, clean coffee, pea berry, parchment and
partial dry cherry didn’t showed significance
difference as compare to others seed source
(Table 3).
The tap root length and no of lateral showed no
significant difference in all cases.

Coffee Peaberry as A Potential Seed Source for Production
International Journal of Research Studies in Science, Engineering and Technology V7 ● I9 ● 2020 34
Table3. Destructive parameters of coffee seedlings as influenced by different seed growth stage and preparation
Seed type
Destructive parameter
Total dry
matter (g)
Root growth
Dry wt. (g)
Tap root length
(cm)
No. of
lateral
Shoot
Leaf
Root
Fresh cherry
1.52bc
1.77b
1.70ab
4.99b
23.60
20.25
Partial dry cherry
2.78 b
2.29ab
1.19b
6.25ab
21.64
23.67
Green berry
1.28 c
1.66b
1.28b
4.21b
20.52
21.83
Clean coffee
4.12a
4.88a
2.97a
11.97a
30.33
25.92
Pea berry
3.65a
4.37ab
2.55a
10.57ab
20.58
23.67
Parchment
3.11ab
3.78ab
2.60a
9.49ab
21.38
25.33
S.E
0.88
0.86
0.37
1.98
2.19
2.31
C.V (%)
55.72
47.73
31.63
43.49
16.52
17.10
Varietal Difference in Coffee Pea Berry
The study conducted on the pea berry
occurrence in different selection and hybrid
coffee seeds showed; there is a varietal
difference in pea berry seeds bearing proportion
among all coffee varieties and canopy classes
i.e. compact type, intermediate, open and
hybrid. The higher the pea berry proportion was
found from hybrid coffee variety which is about
16% and the compact class is 7.53%,
intermediate 7.16%, open types 9.22% and the
high land coffee varieties 5.35%. The overall
mean pea berry proportion in all pure lines
classes is 7.31%. The proportion of pea berries
could also vary between varieties depending on
the level of tolerance of the variety to
environmental stresses or environmental
condition.
The hybrid seed gave 16% of pea berry which is
the highest and two fold of than the selection,
this is because of in hybrid coffee there is
insufficient pollination due to failure of the
agents of pollination (e.g. insect, wind), and
incompatibility of the two parents during
pollination and the less or imperfect fertilization
during field crossing or hand pollination and
incompatibility of the two parents during
pollination.
Table4. Ethiopian coffee varieties and mean proportion of pea berries over two cropping seasons at Jimma
Pure line coffee varieties
Hybrid coffee
variety
Compact
canopy
class
Pea
berry
%
Inter
mediate
canopy
class
Pea
berry
%
Open
canopy
class
Pea
berry
%
High land
coffee
Pea
berry
%
Hybrid
coffee
Pea
berry
%
74110
10.15
7487
6.85
741
6.34
Yachi
8.88
Gawe
16.22
74112
6.43
Meoftu
9.46
754
9.31
Wush Wush
3.24
74140
5.32
Dessu
5.18
75227
10.17
BunoWoshi
3.50
74158
7.10
Mean
7.16
744
11.07
MerdaCheriko
5.76
74165
8.67
Mean
9.22
Mean
5.35
Mean
7.53
Pea berries seed source seedlings have ability to
flower and give yield like the normal beans
coffee plant. The yield obtained from the pea
berry seed source plantation was range from
831.4kg/ha, 947.7kg/ha and 1500kg/ ha clean
coffee for three successive cropping season.
Unlike the works of Melkam et al, (2014) pea
berries in this study are considered aspure,
because of the seed can germinate, emerge,
grow and followed by giving flower and good
crop. Therefore, it is genetically pure seed.
Pea berry may not be predominantly a heritable
character, because seeds produced from coffee
trees raised from pea berries will not develop all
in to pea berries in this study. Like under
normal condition, some seeds may turn in to pea
berries because of that may cause flower
abortion and insufficient pollination due to
failure of the agents of pollination. Since the
embryo development is unaffected, pea berries
can germinate and produce seedlings as of the
normal seed.

Coffee Peaberry as A Potential Seed Source for Production
35 International Journal of Research Studies in Science, Engineering and Technology V7 ● I9 ● 2020
In addition, as indicated in all growth, non
destructive and destructive parameter and the
bearing potential of the pea berry seed is
perform as good as the normal seed at nursery
and field level.
Since the inception of distribution of coffee
seeds from the Ethiopian national coffee
research center, the Jimma agricultural research
center distributed 789230kg different types of
coffee variety seeds throughout the coffee
growing regions of Ethiopia. In addition from
the above amount of seeds 7% pea berries seeds
are sort out from the distributed coffee seeds.
SUMMARY AND CONCLUSION
Pea berry beans are not ‘’male’’ and genetically
it is pure seed. Pea berries can germinate in the
same way as normal beans and produce normal
seedlings to be used in modern coffee
plantation. The pea berries seedlings can grow
as normal coffee tree plant in the field and the
trees can flower and bear potential crop. Seeds
produced from coffee trees raised from pea
berries will not develop all in to pea berries.
Any developer can use it as a pure and healthy
seed for raising seedlings and transplant at the
field. Therefore, it is important to remind not to
exclude or sort out during seed preparation. In
general, this research highlights strongly the
potential to use pea berry seed as a seed source
mainly for hybrid coffee varieties use of clean
seeds prepared from known coffee varieties and
strengthen coffee seed science and technology at
the national level.
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