Genetic progress has brought about increase in yield potential per se for almost all production areas around the world. The present study examines the relationship of groundnut yield with year of release, yield components and other agro-morphological traits using aggregative data from 1976 to 2012 to calculate genetic gain in groundnut grain yield across four locations in Eastern Ethiopia. The direct method, that compares cultivars with their year of release, was used. The relative gain for groundnut grain yield was 1.08% since 1976. A deeper understanding of these issues facilitates the identification of specific yield-limiting factors that can be used for future breeding strategies. Grain yield, 100 seed weight, plant height and harvest index were significantly correlated with year of release for tested locations, emphasizing the most promising traits for groundnut breeders in the past. These traits were also responsible for the significant genetic progress in groundnut yield in Ethiopia since 1976. Further improvement in the yield potential of groundnut will have to involve increase in other traits, like pod weight per plant, seed weight per plant, that have shown significant positive correlation with grain yield.

1. Genetic Progress for Yield, Yield Components and Other Agronomic Characters of Groundnut (Arachis Hypogea L.) Cultivars in Eastern Ethiopia
IJPBCS
Genetic Progress for Yield, Yield Components and Other
Agronomic Characters of Groundnut (Arachis Hypogea
L.) Cultivars in Eastern Ethiopia
Zekeria Yusuf*1, Habtamu Zeleke2, Wassu Mohammed2, Shimelis Hussein3, Arno Hugo4
1Biology Department, Haramaya University, Dire Dawa, Ethiopia.
2School of Plant Science, Haramaya University, Dire Dawa, Ethiopia.
3Department of Crop Science, University of Kwazulu-Natal, Durban, Republic of South Africa.
4Department of Food Science, University of Free State, Bloemfontein, Republic of South Africa.
Genetic progress has brought about increase in yield potential per se for almost all production areas
around the world. The present study examines the relationship of groundnut yield with year of release,
yield components and other agro-morphological traits using aggregative data from 1976 to 2012 to
calculate genetic gain in groundnut grain yield across four locations in Eastern Ethiopia. The direct
method, that compares cultivars with their year of release, was used. The relative gain for groundnut
grain yield was 1.08% since 1976. A deeper understanding of these issues facilitates the identification of
specific yield-limiting factors that can be used for future breeding strategies. Grain yield, 100 seed weight,
plant height and harvest index were significantly correlated with year of release for tested locations,
emphasizing the most promising traits for groundnut breeders in the past. These traits were also
responsible for the significant genetic progress in groundnut yield in Ethiopia since 1976. Further
improvement in the yield potential of groundnut will have to involve increase in other traits, like pod weight
per plant, seed weight per plant, that have shown significant positive correlation with grain yield.
Key words: relative genetic gain, genetic progress, grain yield, groundnut
INTRODUCTION
Documentation of the contribution of plant breeding to a
given crop yield improvement and evaluation of the past
gains are useful for identifying areas with potential for
planning a future breeding program (Waddington et al.,
1986). Evans (1993) advocated that an understanding of
changes produced by crop breeding on grain yield and
its determinants were important to evaluate the efficiency
of past improvement work on the advances in genetic
yield potential, and to define future selection criteria to
facilitate further progress. Genotype, environment and
management interact to determine the yield of a crop.
However, no method of estimating long-term
improvement progress can completely separate genetic
effects per se and their interaction effect. Nevertheless,
evaluation of popular cultivars from different years in
common environments is the most comprehensive and
direct method that have been used to estimate progress
in yield improvement (Lange and Federizzi, 2009).
Besides quantifying the progress obtained in a certain
period, the genetic gain analysis also enables
aggregation of other information such as comparison of
the gains obtained with the use of different breeding
strategies or in different environments (Specht and
Williams, 1984).
*Corresponding Author: Zekeria Yusuf, Biology Department,
Haramaya University, Dire Dawa, Ethiopia. Email Address:
zakoyusuf@yahoo.com
Co-authors: wubeno@yahoo.com (H. Zeleke),
wasmoha@yahoo.com (W. Mohammed),
shimelish@ukzn.ac.za (S. Hussein), HugoA@ufs.ac.za (A.
Hugo)
International Journal of Plant Breeding and Crop Science
Vol. 4(2), pp. 237-242, July, 2017. © www.premierpublishers.org. ISSN: 2167-0449
Research Article

2. Genetic Progress for Yield, Yield Components and Other Agronomic Characters of Groundnut (Arachis Hypogea L.) Cultivars in Eastern Ethiopia
Yusuf et al 238
Table 1. Description of locations used in the study
Locations Altitude(m) A.S.L Temperature (0
C) Av. Annual RF(mm)
Babile 1773 20.0 790
Fedis 1611 21.0 750
Hirna 1763 19.7 1011
Mechara 1790 20.4 1018
This kind of information contributes to the understanding
of past events, allows elaboration of new strategies,
adoption of corrective methods and more efficient
resource allocation that together result in an increase in
the breeding progress efficacy (Lange and Federizzi,
2009). Genetic progress can be estimated from multi-
environmental trial (MET) data (Vencovsky et al., 1988;
Breseghello et al., 1998) which are routinely carrying out
by annual species breeding programs for assessment of
new commercial cultivars.
Progress made in genetic yield potential and associated
changes in morpho-physiological attributes produced by
genetic improvement and benefits obtained, thereof,
have been documented in different crops in different
countries (Austin et al.,1989) by comparing old and
modern varieties. Besides the strategies mentioned
previously, genetic yield gain for a given plant crop
depends on the frequent re-evaluation of the genotypes
and methodologies employed by the breeding program.
Determination of genetic progression estimates is
fundamental in decision making processes concerning
the maintenance or implementation of novel selection
methodologies in breeding programs (Soares et al.,
2005).
The consideration of the breeding method employed is
crucial to estimate the genetic progression, since there
are methods that directly compare previous cultivars to
new ones (Rodrigues et al., 2007; Souza et al., 2007)
and indirect methods that analyze the experiments
conducted by breeding programs as a function of a
desired period of time for which the genetic gain is to be
determined (Abreu et al., 1994). The indirect method is
based on multi-locality competition assays for cultivars
and lines used as reference control-cultivars, which are
shared by all experiments during the period of time in
consideration. The control-cultivar must be a good
representative of the agronomical features of interest to
the market, especially when the investigated feature is
yield. In the absence of standard control-cultivars,
adjusted arithmetical means of the tested treatments can
be used to estimate the genetic gain for each year (Matos
et al., 2007). In the present study the direct method was
used to investigate the genetic progress of groundnut
varieties in major groundnut growing localities in Eastern
Ethiopia; to assess the progress made in yield, and traits
most contributing to yield of groundnut through 1976-
2012 breeding period in Ethiopia; to identify future
breeding strategy for groundnut genotypes in Ethiopia
MATERIALS AND METHODS
The experiment was carried out across four locations viz.
Babile, Fedis, Hirna and Mechara during 2015 growing
season in Ethiopia under rain fed condition (Table 1). The
experimental materials consisted of sixteen groundnut
genotypes including variety (Table 2), which were
released by Ethiopian Institute of Agricultural research
(EIAR) between 1976 to 2012. The treatment consisted
of sixteen groundnut genotypes with three replications in
four locations and was planted in a randomized complete
block design (RCBD) so that the total number of
treatment was being16genotypes x 3 replications x 4
locations=192. Each entry was planted in a plot having 2
rows of 3-meter length. The spacing between rows and
plants was 60cm and 15cm respectively. Each row had
12 plants. Two seeds were planted in each hole and hill
was thinned to one after emergence. The spacing
between plots was 1m. The net plot size was 5.4 m2.
Following land preparation, groundnut seeds were
planted and the treatments were being looked after for
recommended agronomic practices including weeding,
hoeing, fertilizer application and the necessary plant
protection.
Data were recorded for 12 agro-morphological
characters viz. plant height (PH, cm), number of mature
pods per plant (NMP), number of primary branches per
plant (NBP), above ground biomass per plant (AGBP, g),
pod weight per plant (PWP, g), number of seeds per
plant(NSP), seed weight per plant (SWP, g), shell
percentage (SHP %), 100 seed weight (100SW, g),
Harvest index (HI%), number of seeds per pod
(NSPOD), grain yield per hectare (GY, kg/ha). The pods
from entire plot were harvested and immature pods were
removed. The mature pods were air dried, cleaned and
weighed. The data were recorded on five randomly
selected plants in each entry or replication. The annual
rate of gain in grain yield potential and changes produced
on yield related traits were estimated by mean value
regression for each character specific to varieties against
the year of variety release. The absolute yield gains (kg
ha-1 year-1) of grain yield was estimated by linear
regression using the following equation (Wu et al., 2014):
y= ax +b; where ‘‘y’’ is the average yield for each
genotype, ‘‘x’’ is the year of release, ‘‘a’’ is the absolute
yield gain, or regression coefficient estimating yearly
gains; and ‘‘b’’ is the intercept. The relative annual gain
achieved over the last 36years (1976 to 2012) for

3. Genetic Progress for Yield, Yield Components and Other Agronomic Characters of Groundnut (Arachis Hypogea L.) Cultivars in Eastern Ethiopia
Int. J. Plant Breed. Crop Sci. 239
Table 2. Genotypes used in the study with their year of release and pedigree
Genotypes Year of Release Pedigree/origin
Shulamith 1976 Introduced
NC343 1986 Introduced
Roba 1989 Introduced
Sedi 1993 Developed through selection
Bulki 2002 Developed through hybridization
Lote 2002 Developed through hybridization
Manipeter 2004 Introduced
Werer 961 (ICGV-87108) 2004 Developed through hybridization
Werer 962 (ICGV-86928) 2004 Developed through hybridization
Werer 963 (ICGV-86644) 2004 Developed through hybridization
Oldhale 2008 Developed through selection
Tole1 2008 Developed through selection
Tole2 2008 Developed through selection
Fetene (ICGV-93370) 2009 Developed through hybridization
Baha gudo (ICGV-88357) 2012 Developed through hybridization
Baha jidu (NC-AC-2748X CHICO) 2012 Developed through hybridization
Table 3. Mean yield of groundnut varieties with performance relative to the oldest variety
Genotypes National Yield
Potential (kg/ha)
Year of
release
Trial GY (kg/ha) Performance relative to the
oldest variety (Shulamith) (%)
Shulamith 2750 1976 2694 ---
NC343 3000 1986 3423 27.0
Roba 4000 1989 3673 28.6
Sedi 1800 1993 2397 -8.1
Bulki 2100 2002 2507 -7.8
Lote 2300 2002 2831 5.5
Manipeter 2645 2008 3792 38.8
Werer-961 (ICGV-87108) 2645 2004 3121 11.0
Werer-962 (ICGV-86928) 2939 2004 3763 34.0
Werer- 963 (ICGV-86644) 2157 2004 2143 -14.6
Oldhale 2000 2008 2755 2.8
Tole-1 1800 2008 3500 29.0
Tole-2 5000 2008 3670 28.0
Fetene (ICGV-93370) 6072 2009 3373 18.5
Baha gudo (ICGV-88357) 1965 2012 3650 28.0
Bahajidu (NC-AC-2748X Chico) 2079 2012 3208 14.0
Overall mean 3156 14.0
groundnut genotypes in Ethiopia was determined as a
ratio of genetic gain to corresponding mean value of
oldest variety or average yield of all varieties and
expressed as percentage, calculated the following
equation:
Relative yield gain =
absolute yield gain
mean of oldest variety
x100%
In order to calculate the gain as percentage per year, the
percentage gain for each selection cycle was divided by
the average number of years per selection cycle.
Pearson product moment correlation coefficient among
all characters was computed using means of each
variety in each year using SAS PROC CORR procedure.
Stepwise regression analysis was done using SAS
PROC REG procedure to identify best contributing traits
to grain yield as a dependent variable.
RESULTS AND DISCUSSION
The average grain yield of the 16 groundnut varieties
released between 1976 to 2012 and their relationship
with the oldest variety (Shulamith) was indicated in Table
3. The overall increase in grain yield over the oldest
variety, Shulamith was estimated to be 14% (kg/ha)
considering all varieties in the trial. Hence, grain yield
increased substantially with the release of some new
improved groundnut varieties while the yield of some of
theothers were lower than the oldest variety. The results
obtained in this study were in agreement with those of
Naeem et al. (2009) who reported that improved
groundnut varieties produced 10.96% higher pod yield
and 23.83% higher seed yield over the check variety.
However, this result was not consistent with Fikreet al.
(2012) who reported all subsequent groundnut varieties
had higher yield than the oldest variety. This gives an

4. Genetic Progress for Yield, Yield Components and Other Agronomic Characters of Groundnut (Arachis Hypogea L.) Cultivars in Eastern Ethiopia
Yusuf et al 240
Figure 1. Regression of mean grain yield across successive years of release
Table 4. Mean grain yield, absolute yield gain, and relative yield gain evaluated across four locations.
Trait Trait mean (kg/ha) Intercept Absolute gain (slope) Relative gain(%)
PH 29.55 -252.98 0.14** 0.66
NMP 41.80 207.12 -0.08 -0.22
NBP 11.43 -23.66 0.02 0.18
AGBP 67.68 -57.33 0.06 0.10
PWP 40.09 129.17 -0.05 -0.10
SWP 33.68 -215.86 0.13 0.54
NSP 66.54 154.73 -0.04 -0.08
ShP 61.58 -119.29 0.09 0.17
100SW 55.48 -812.72 0.43** 0.88
HI 26.61 -207.15 0.12* 0.51
NSPod 1.59 3.23 -0.001 -0.07
GY 3156.2 -54019 29.0** 1.10
PH: plant height; NMP: number of mature pod per plant; NBP: number of branches per plant; AGBP: above
ground biomass per plant; PWP: pod weight per plant; SWP: seed weight per plant; NSP: number of seeds
per plant; SHP: shelling percent; 100SW: 100 seed weight; HI: harvest index; NSPod: number of seeds per
pod; GY: grain yield (kg/ha).
insight for possible future opportunities to exploit the
genetic potential of the crop for enhanced production.
As the slope of the linear regression (Table 4 and fig. 1)
of NMP, NBP, AGBP, PWP, SWP, NSP, SHP and
NSPOD for the time period of 1976 to 2012 did not differ
significantly from zero indicating that no genetic gain can
be estimated for these traits. This shows that breeding
programs so far employed has made little improvement
of these characters or due to the recent erratic climatic
conditions or the use of some unfavorable locations. To
overcome such problems, the present study
recommends the consideration of more number of
replications as many locations as possible. In contrast,
the relative gain for PH, 100SW and GY were
significantly different from zero. However, associated
with low coefficient of determination (R2
) results in
difficulty of generalization. This finding doesn't agree with
previous report by Fikire et al., 2012 who obtained
significant genetic gain for other traits like PWP, HI, and
SWP.
The yield levels varied significantly from 2143 to 3763
kg/ha among the 16 varieties (Table 4). A linear
regression equation showed that the relationship
between yield and year of release was highly significant
(P ≤ 0.01) as indicated in fig 1. Across 36 years of
groundnut breeding, 1.1% improvement of yield or 0.03%
increase per year was achieved (Table 4). Ntare and
Waliyar (1994) reported similar result for the large-
seeded Virginia type groundnut, with a relative genetic
gain of 1.3-3.2% per year, which is in agreement with the
findings of this study. There were no indication of yield
potential plateau in groundnut varieties over the period of
the study (Fig 1) which indicates that further
improvement is possible to increase yield and this
provides clues for breeders to further exploit (increase)
the yield potential of the existing groundnut varieties.
Implication on future breeding strategy
Correlation analyses of yield components with year of
release provide important selection criteria for the further

5. Genetic Progress for Yield, Yield Components and Other Agronomic Characters of Groundnut (Arachis Hypogea L.) Cultivars in Eastern Ethiopia
Int. J. Plant Breed. Crop Sci. 241
Table 5. Correlation coefficients of the year of release with yield components and other agronomic traits
Trait CV (%) PH NMP NBP AGBP PWP SWP NSP ShP 100SW HI NSPod GY (kgha−1
) year
PH 10.84 0.21** 0.06 0.49** -0.07 0.48** 0.06 0.07 0.09 -0.34** -0.30** -0.003 0.23**
NMP 23.86 0.35** 0.43** 0.51** 0.31** 0.64** -0.03 -0.15* -0.09 -0.33** 0.21** -0.06
NBP 24.37 0.42** 0.18* 0.21** 0.25** -0.19** 0.09 -0.24** -0.28** 0.26** 0.04
AGBP 28.98 0.36** 0.31** 0.11 -0.24** 0.21** -0.61** -0.52** 0.15* 0.02
PWP 24.72 0.06 0.48** -0.02 0.31** 0.14 -0.07 0.32** -0.03
SWP 28.90 0.21** 0.15* 0.17* 0.02 -0.26** 0.03 0.08
NSP 21.93 0.09 -0.23** 0.23** 0.16* 0.14 -0.02
ShP 6.24 0.06 0.39** 0.12 0.10 0.11
100SW 2.32 0.09 -0.26** 0.34** 0.27**
HI 17.36 0.41** 0.08 0.14*
NSPod 8.84 -0.22** -0.03
GY 14.6 0.23**
year
PH: plant height; NMPP: number of mature pod per plant; NBP: number of branches per plant; AGBP: above ground biomass per plant; PWP:
pod weight per plant; SWP: seed weight per plant; NSP: number of seeds per plant; SHP: shelling percent; 100SW: 100 seed weight; HI: harvest
index; NSPod: number of seeds per pod; GY: grain yield (kg/ha).
improvement of yield potential in breeding programs (Wu
et al., 2014). Relationships between grain yield and year
of release were positive and significant. Moreover, PH,
100SW and HI were also significant and positively
related to year of release (Table 5). However, the other
characters including NMP, NBP, AGBP, PWP, SWP,
NSP, SHP and NSPOD did not depict strong
relationships with year of release. Similarly, groundnut
grain yield revealed positive and strong relationships with
NMP, NBP, PWP, and 100SW. Other yield components
did not demonstrate consistent relationships with grain
yield. These findings imply that, since 1976, PH, 100SW,
and HI traits have been widely used as promising traits
for groundnut yield progress in Ethiopia. The future
breeding strategy further more should focus on other
traits that are positively and significantly correlated with
grain yield including SWP, PWP, NMP, NBP and others.
The coefficients of variance (CV) for all parameters are
given in Table 5. The results show that AGBP and SWP
had maximum values, whereas 100SW and SHP had
among the minimum values. Greater CV of AGBP and
SWP, implied that it has been experienced as easy
identifiable agronomic trait for plant breeder in a long
time. Selecting large SWP was possible due to greater
grain weight. Lower CV of 100SW and SHP suggested
that it is difficult to improve due to ceiling limit although it
has been regarded as promising trait. This finding is
comparable to several previous reports (Zhou et al.,
2007a; Tian et al., 2011; Wu et al., 2014)
CONCLUSION
Groundnut grain yields have risen in Ethiopia since the
1976, concomitant with changes in crop management
and with the utilization and improvement of new varieties.
However, the yield obtained is not sufficient. Genetic
improvements can be related to factors that promote
greater efficiency in grain production, and those that
provide increased tolerance to abiotic and biotic
stresses. The major challenge for groundnut production
is Ethiopia is being biotic stress due to pathogenic fungi,
nematodes and insect pests. The small yield gain
obtained during the period might be due to these biotic
stresses. Present results demonstrate the overwhelming
importanceof plant breeding in improving groundnut
productivity in Ethiopia. Significant increases in grain
yield, 100seed weight, plant height and harvest index
have contributed to the continuousgenetic gain in yield
potential groundnut from 1976 to 2012 across locations
in Eastern Ethiopia. Despite the genetic progress and
cultivation technologies employed, the continuously
growing population creates a mismatch that representsa
serious challenge for future food security (FAO, 2006). It
can be suggested that integrated crop
managementshould be prioritized as an approach for
sustainableagricultural research and implementation.
Thepresent study suggests that increasing genetic gain
for groundnut yield is the most crucial strategy for
increasing groundnut production.
ACKNOWLEDGEMENTS
Authors are grateful to Haramaya University School of
graduate Studies and HU Research Office for their
funding support, Mechara and Pawe Agricultural
Research Centers for their provision of plantation land
and other supports in agronomic management and data
collections.
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Accepted 2 July, 2017
Citation: Yusuf Z, Zeleke H, Mohammed W, Hussein S,
Hugo A (2017). Genetic Progress for Yield, Yield
Components and Other Agronomic Characters of
Groundnut (Arachis Hypogea L.) Cultivars in Eastern
Ethiopia. International Journal of Plant Breeding and
Crop Science 4(2): 237-242.
Copyright: © 2017 Yusuf et al. This is an open-access
article distributed under the terms of the Creative
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unrestricted use, distribution, and reproduction in any
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cited.