Genetic Variability on Seed Yield and Related Traits of Elite Faba Bean (Vicia
faba L.) Genotypes
Faba bean is one of the most important cool season crops in
the highlands of Ethiopia and the country is considered as the secondary center
of diversity. This study was conducted at Haramaya, Boreda and Hirna districts
of Eastern Hararghe from 2006 to 2008 cropping season using twenty five elite
genotypes of faba bean to determine the extent and pattern of genetic diversity
for seed yield and related traits. The treatments were arranged in a randomized
complete block design with three replications. The data were subjected to the
analyses of variance using the SAS program. The mean squares due to genotypes
were highly significant for seed yield (p<0.01) indicating the existence
of sufficient genetic variability for seed yield. Mean squares due to the interaction
between year and location were highly significant for all the traits studied
(p<0.01). High genotypic coefficient of variation (10093.53%) was observed
for seed yield followed by number of seeds per plant (325.45%). The estimated
values of phenotypic variances were in the range of 0.60 for number of seeds
per pods to 196564.64 for seed yield. Genetic gains that expected from selecting
the top 5% of the genotypes, as a percent of the mean, varied from 12.32% for
number of seeds per plant to 35.46% for seed yield. The average linkage technique
of clustering produced a more understandable portrayal of the 25 faba bean genotypes
by grouping them into five clusters. The maximum distance was found between
cluster three and five (D2 = 691.47). Thus, the materials tested
in the entire experiment will be maintained for further breeding program.
Received: June 30, 2012;
Accepted: August 11, 2012;
Published: September 03, 2012
Faba bean (Vicia faba L.) is a grain legume cultivated for multiple
usages because of its high nutritional value excellent source of protein ranges
from 27-34% (Duc, 1997; Haciseferogullari
et al., 2003). Ethiopia is the second largest faba bean producing
countries in the world (Hebblethwaite et al., 1993).
According to Duc et al. (2010), faba bean is
spread from the principal center to Ethiopia and from Mediterranean region to
Europe to form a third center of importance. They also reported about 1118 faba
bean ex situ collection in Ethiopia in 2008 which were mostly contains
improved cultivars and farmers population. The crop is well grown in the
highlands of Ethiopia ranged from 1800-3000 m.a.s.l. with annual rain fall of
700-1000 mm (Yohannes, 2000). It was planted to 3.88%
of the grain crop area with total annual grain production of 3.43% of the country
(CSA, 2011). It is the main food source that supplements
a low cost alternative to animal protein subsistent farmers by providing 18-32%
protein (Hanelt and Mettin, 1989). It also cash source
for local farming community in particular and foreign currency for the country
in general. Moreover, the crop can be used as break crops where cereal based
mono-cropping system is dominated, replenish soil nutrients through biological
nitrogen fixation and reduce biological pests (Chintalapati,
The crop prevails high degree of genetic variability due to the fact that the
presence of high percentage of out crossing (Polignano and
Zeuli, 1985; Hanelt and Mettin, 1989). A large genetic
variability has already been identified in faba bean in terms of floral biology,
seed size and composition, yield potential efficiency of symbiotic nitrogen
fixation and tolerance to several biotic and a biotic stresses (Duc
et al., 2010). It is obvious that genetic gain from selection depends
on the extent of genetic variation and on the magnitude of the heritable portion
of these variations. To this effect, having the information on the degree of
genetic variability exist in the faba bean is critical to design effective breeding
Therefore, this piece investigation was conducted to determine the extent and
pattern of genetic diversity for seed yield and related traits and to establish
fundamental genetic facts such as heritabilities and covariances of traits of
interest for further improvement of faba bean.
MATERIALS AND METHODS
The field experiment was conducted at three locations: Haramaya, Boreda and
Hirna during 2006, 2007 and 2008 main cropping seasons. Haramaya has an altitude
of 1980 m above sea level. It was in semi-arid sub-tropical belt of eastern
Ethiopia. The area receives an average annual rainfall of 870 mm. The soil is
characterized as a fluvisol with a pH of 7.4 (Solomon, 2006).
While Hirna situated under 9°13N and 41°6E has an altitude
of 1763 m above sea level and Boreda has an altitude of 2800 m above sea level
average rain fall of 1064 mm and annual temperature of 16-28°C.
Treatment and experimental design: Twenty five elite genotypes of faba
bean along with a commercial variety (Tesfa) and a local check were considered
in this study. Treatments were arranged in a randomized completely block design
with three replications. Seeding was done in a plot of four rows with four meter
length and regular spacing of 10 cm between plants and 40 cm between rows. The
layout and randomization were as per the standard procedure set by Cochran
and Cox (1957). Weeding and other cultural practices were done as per the
recommendations adopted for the respective sites.
Collected data: The following data were collected either from whole
plot or from ten sample plants from each plot. Mean values of these samples
were utilized to estimate the performance of each germplasm accession for the
traits under consideration. The traits number of pods per plant, number of seeds
per plant, number of seeds per pod and seed yield per plot were considered under
Homogeneity test: Before proceeding with the analysis of variance
for each variable, tests were made for homogeneity of variances using the Fmax
test as given by the following formula:
and tested at [(g-1) (r-1)] degree of freedom of mean square where g and r
are the number of genotypes and replications, respectively. Then, the table
of the probability distribution of Fmax consulted.
Analysis of variance: The data were subjected to the analyses of variance
(ANOVA) and combined analysis of variance over environment for Randomized Complete
Block Design RCBD was performed using the SAS program (SAS,
The total variability for the traits was quantified using pooled analyses of
variance over three years and locations using the following model:
Pimkt = μ+ym+lt+ri(m)(t)+gk+(gy)km+(yl)mt+(gl)kt+(ylg)mtk+eimkt
||Phenotypic value of kth genotype under ith replication during
mth year at tth location with replication i, location t and year m
||The effect of replication i with in year m and location t
||The effect of kth genotypes
||Grand mean and (gy)km, (yl)mt, (gl)kt and
(ylg)kmt = the interaction effects and
Partitioning of the total variation into components due to genotype ((σg2),
environment (σe2) and genotype by environment interaction
(σge2) deviations was performed from the analyses
of variance by calculating expected mean squares and similarly, the components
from pooled analysis of variance over years and locations were calculated.
Variance component: The coefficients of variations at phenotypic and
genotypic levels were estimated using the formula adopted by Johnson
et al. (1955). Broad-sense heritability (h2) was estimated
for pooled analyses over three years and locations using the formula adopted
by Allard (1960). Genetic advance in absolute unit (GA)
and percent of the mean (GAM), assuming selection of the superior 5% of the
genotypes, was estimated in accordance with the methods illustrated by Johnson
et al. (1955).
Distance analysis: Grouping the germplasm in to different groups based
on multiple traits including the seed yield was conducted in this investigation
by following the average linkage. Thus the analysis was computed based on multivariate
analysis using Mahalanobis D2 statistic (Mahalanobis,
1936). Squared distance (D2) for each pair of genotype combinations
was computed using the formula suggested by Singh and Chaudhary
RESULTS AND DISCUSSION
It can be seen from Table 1 that the mean squares due to
year were highly significant (p<0.01) for the traits seed yield (28763.58),
number of seeds and pods per plant which was 16889.97 and 1390.26, respectively.
However, non significant was observed for number of seeds per pod.
||Analysis of variance for four traits of faba bean germplasms
tested over three cropping seasons (2006-2008) and three locations (Haramaya,
Boreda and Hirna)
|*,**Significant at 0.05 and 0.01 probability level,
respectively, nsNon significant, MSY: Mean square due to year,
MSL: Mean square due to location, MSR: Mean square due to replication, MSG:
Mean square due to genotypes, MSYL: Mean square due to the interaction between
year and location, MSYG: Mean square due to the interaction between year
and genotypes, MSLG: Mean square due to the interaction between location
and genotypes, MSYLG: Mean square due to the interaction between year and
location and genotypes, MSE: Mean square due to error, CV%: Coefficient
of variation in percentage. βValues in parenthesis indicate
degrees of freedom, SPP: No. of seeds per pod, PPL: No. of pods per plant,
SPPL: No. of seeds per plant, SYLD: Seed yield in g per plot
||Estimates of minimum, mean and maximum value, variance and
coefficient of variation at phenotypic (σ2p), genotypic
(σ2g) level, heritability in broad sense (h2%),
genetic advance in absolute (GA) and percent of mean (GAM) for four traits
of Vicia faba
|SPP: No. of seeds per pod, PPL: No. of pods per plant, SPPL:
No. of seeds per plant, SYLD: Seed yield in g per plot
Similarly, except for number of pods per plant, the mean squares due to location
were highly significant for all traits (seed yield, (76070.50) number of seeds
per pant and per pod with 926.00 and 39.01, respectively, indicating that there
are differences between the nine environments which are significant enough to
see the genetic performance of faba bean germplasm. It is evident from the results
that mean squares due to genotypes (2262.98) were highly significant for seed
yield, indicating the existence of sufficient genetic variability for seed yield.
Mean squares due to the interaction between year and location were highly significant
for all the traits studied. Mean squares due to the interaction between location
and genotype were non-significant for all traits, except for seed yield.
The elite faba bean evaluated under Eastern Ethiopia in this study showed significant
phenotypic variability in terms of seed yield and yield attributes. Therefore,
future breeding program should take the finding as to improve for the benefit
the welfare of the community. These results are similar with the findings of
other scholars like Asfaw et al. (1994) and Yohannes
(2000) with faba bean and also with other crops (Fahmi
et al., 2012).
Range of parameters: The maximum seed yield (7031 g/plot) and the minimum
(136.60 g/plot) with the over all mean seed yield per plant of 741.01 g/plot
(Table 2). The result from this investigation is in agreement
with the previous reports from Ethiopia (Asfaw et al.,
1994; Dawit et al., 1994; Getahun,
1998) who reported the existence of considerable variation for the morpho-agronomic
traits in faba bean landraces.
High genotypic coefficient of variation (10093.53%) This is not the CV used
to measure the validity of the experiment. It is the value the observed genotypic
or phenotypic variability among the genotypes under study expressed in percentage
and the value indicated that there was variability (diversity) among the genotypes
and no need to transform the data was observed for seed yield followed by number
of seeds per plant (325.45%). The estimated values of phenotypic variances were
in the range of 0.60 for number of seeds per pods to 196564.64 for seed yield
(Table 2). The lowest and highest genotypic variances were
found for number of seed per pods (0.17) and seed yield per plot (74793.99),
respectively. There fore, the result indicated the existence of variability
in the tested faba bean genotypes.
The results depicted in Table 2 showed that estimates of
heritability in broad sense were medium for number of pods per plant (57.23%),
indicated it may respond moderately to phenotypic selection (Singh
and Ceccarelli, 1996). Moreover, the value is low for the rest of the traits
including seed yield, indicating limited possibility of improvement for this
character through selection. In earlier studies (Banziger
and Edmeades, 1997), the findings are thus only partially in agreement with
the results obtained in the present investigation. The probable cause of the
disparity could be due to the fact that the heritability of a given trait refers
to a particular population under a particular condition or environment. The
effectiveness of selection for a trait depends on the relative importance of
the genetic and environmental factors in the expression of phenotypic differences
among genotypes in a population.
Estimation of expected genetic advance: Genetic gains that expected
from selecting the top 5% of the genotypes, as a percent of the mean, varied
from 12.32% for number of seeds per plant to 35.46% for seed yield, indicating
an increase of 12.32 to 35.46% made by selection on these traits under similar
conditions (Table 2).
|| Mean and range of genetic divergence in seed yield and related
traits of the five clusters of Vicia faba
|SPP: No. of seeds per pod, PPL: No. of pods per plant, SPPL:
No. of seeds per plant, SYLD: Seed yield in g per plot
||Pair wise generalized squared distance (D2) among
5 clusters constructed from 25 elite faba bean genotypes
|*,**Significant at 5 and 1%, respectively
The low values of expected genetic advance for number of seeds per plant was
due to low variability for the traits indicated by the low GCV and PCV values.
The low expected genetic advance for number of seeds per pod in this study was
due to low variability for the trait. Therefore, even if heritability estimates
provide basis for selection on phenotypic performance, the estimates of heritability
and genetic advance should always be considered simultaneously, as high heritability
is not always associated with high genetic advance (Johnson
et al., 1955).
Clustering of genotypes and divergence analysis: The average linkage
technique of clustering produced a more understandable portrayal of the twenty
five faba bean genotypes by grouping them into five clusters, whereby different
members within a cluster being assumed to be more closely related in terms of
the trait under consideration with each other than those members in different
clusters. Table 3 indicates the range (minimum and maximum)
and mean of genetic divergence in seed yield and related traits of the five
clusters. From the analysis, there was range variability in different traits
among clusters. The evaluated materials ranges for the trait seed yield 739.7-785.2
in cluster I, 677.9-726.8 in cluster II, 603.2-633.4 in cluster III and 835.7-881.8
in cluster IV. Therefore, from this finding, the tested faba bean materials
exhibited difference in seed yield and other related traits. The detail account
of the characteristics of each cluster is presented hereunder.
||Cluster I: It consisted of 9 genotypes which were laid
on high in number of seeds per plant and intermediate value in the rest
the traits under consideration
||Cluster II: It consisted of 6 genotypes which were intermediate
for all the traits under studied
||Cluster III: It consisted of 5 genotypes characterized by intermediate
in number of seeds per plant where as, the genotypes in this cluster exhibited
inferior in the rest of the traits including seed yield
||Cluster IV: It had 4 genotypes which exhibited superior in number
of seeds and pods per plant whereas inferior in number of seeds per plant.
These genotypes exhibited intermediate for seed yielding potentials
||Cluster V: It consisted single genotypes which exhibited superior
in seed yielding capacity where as intermediate in other seed contributing
From the estimated distance analysis, under this investigation, all the ten
possible pairs of clusters, differences between thirteen pairs were highly significant
(p<0.01) which ranged from 15.65 between cluster one and two to 691.47 between
cluster three and five (Table 4). The details of each pair
of cluster distances are discussed in the paragraphs below.
The maximum distance was found between cluster three and five (D2
= 691.47). Cluster three constitutes five genotypes while cluster five constitutes
a single genotype (Table 3). The second most divergent clusters
were cluster five and two (D2 = 420.55). Cluster two constitutes
The third most divergent clusters were cluster four and three (D2
= 276.63). Cluster four constitutes 4 accessions including the checks (standard
and local). Genotypes grouped into the same cluster presumably diverge little
from one another as the aggregate characters are measured. Generally, maximum
genetic segregation and genetic recombination is expected from crosses that
involve parents from the clusters characterized by significant distances. In
the present investigation, therefore, crossing of accessions from cluster three
and five will give rise to maximum genetic segregation. This finding is inconsistent
with Gemechu et al. (2005) who reported on evaluation
144 faba bean landraces.
The mean squares due to year were highly significant for all the three traits
except number of seeds per pod. Similarly, except for number of pods per plant,
the mean squares due to location were highly significant for all traits indicating
that there are differences between the nine environments. The mean squares due
to genotypes were highly significant for seed yield, indicating the existence
of sufficient genetic variability for seed yield. High genotypic coefficient
of variation was observed for seed yield followed by number of seeds per plant.
Estimates of heritability in broad sense were medium for number of pods per
plant and low for the rest of traits indicated it may respond moderately to
phenotypic selection. From the result of genetic advance an increase of 12.32
to 35.46% magnitude made by selection.
The average linkage technique of clustering produced a more understandable
portrayal of the twenty five faba bean genotypes by grouping them into five
clusters. From the estimated distance analysis, under this investigation, all
the ten possible pairs of clusters, differences between thirteen pairs were
highly significant and the maximum distance was found between cluster three
and five. This indicates, therefore, crossing of accessions between these clusters
will give rise to maximum genetic segregation.
The authors wish to thank the staff of the Highland Pulse Research Program
at Haramaya University who managed the trial. The financial assistance from
Ethiopian Institute of Agricultural Research for the research work is highly
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