Legume Research

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Legume Research, volume 46 iussue 5 (may 2023) : 579-583

Genetic Enhancement of Yield Traits in Chickpea (Cicer arietinum L.): An Analysis of Selection in Early Segregating Generations

B.S. Patil1,*, C. Bharadwaj2, A.G. Vijaykumar3
1ICAR-Indian Agricultural Research Institute’s Regional Research Centre, Dharwad-580 005, Karnataka, India.
2ICAR-Indian Agricultural Research Institute, Pusa-110 012 New Delhi, India.
3Seed Production Officer (GPB), University of Agricultural Sciences, Dharwad-580 005, Karnataka, India.
  • Submitted18-04-2020|

  • Accepted02-09-2020|

  • First Online 19-12-2020|

  • doi 10.18805/LR-4400

Cite article:- Patil B.S., Bharadwaj C., Vijaykumar A.G. (2023). Genetic Enhancement of Yield Traits in Chickpea (Cicer arietinum L.): An Analysis of Selection in Early Segregating Generations . Legume Research. 46(5): 579-583. doi: 10.18805/LR-4400.
Background: Indirect selection for yield contributing traits in segregating generation is practiced to realize the potential yields. However, the effectiveness of selection either in early or late segregating generation is a debatable issue in self pollinated crops. The issue is addressed in chickpea by analyzing four segregating generations of a cross in the same season. 

Method: A bold seeded desi chickpea variety BGD 103 crossed with JAKI 9218. The segregating generations were advanced up to F5 without selection and retaining part of the seeds in each generation. The populations comprised of 162 F­2 plants, 162 F3, F4 and F5 progeny rows were evaluated during rabi 2018-19. The observations on seed traits were recorded and data was subjected to statistical analyses to estimate correlation among the traits in each generations, inter-generation correlation and heritability.

Result: The range of variation for the traits narrowed with advancement of the generations. The heritability decreased for seed weight, increased for number of pods per plant and number of seeds per plant with the advancement of generation. In all the four generations, seed yields were associated with number of pods per plant, seeds per plant and seed weight. The change in association among seed traits different generations and estimates of inter-generation correlations suggest that simultaneous improvement of seed weight, seed number and seed yield could be achieved by selection in F3 and F4 generations.
The widely followed method for genetic enhancement of target trait in self pollinated crops is through hybridization between selected parents, followed by selection of promising lines in segregating generations. Different methods of selection are employed to isolate promising segregants with improved target traits. The success of isolation of lines with improved target trait depends on the various factors like choice of the parents for hybridization, extent of genetic variability created and heritability. Normally diverse parents were chosen with the objective of generating wide genetic variability and subsequently select promising segregant. In general grain yield is the target trait for most of the breeding programmes. The heritability of grain yield is very low; hence direct selection for improvement of grain yield in segregating population may not be effective. The indirect selection for yield contributing traits in segregating generation is practiced to realize the potential yields. The heritability and correlation in different segregating generations decides the effectiveness of selection and in turn final performance of line at homozygosity. The estimation of heritability and genetic correlation between two generations is very useful for selection in segregating population for the production of new, improved genotypes. There are contrasting genetic theories on the generation in which the selection to be effected. Many studies have shown that selection in early generation for yield contributing traits may be effective (Sharma, 1994; Martin and Geraldi, 2002; Jones and Smith, 2006). This theory assumes that most desirable gene combinations can be identified in the heterozygote condition itself. The opposing theory views that, the proportion of homozygote lines in early generations is very less and selection should be delayed until later generations (Seitzer and Evans, 1978 and Padi and Ehlers, 2008). On the contrary, Yang (2009) proposed that, two or more cycle of early generation selections instead of one cycle of selection is more effective than selection of homozygous lines in later generations unless there are strong non additive effects. In some of these studies, the generations were grown in different years. As a result success of selection is affected by environmental variations (Whan et al., 1981 and 1982). Therefore the environmental effect must be considered in assessing relative merit of each of these theories (Whan et al., 1982). The present investigation is aimed at simultaneous evaluation of different segregating generations in the same year so as to nullify the environmental effect on expression of traits in different segregating generations.

 Chickpea is a self pollinated, diploid (2n = 16) grain legume crop grown in a wide range of environments. The seed traits viz., seed size/weight, seed number, pod number etc are the major yield contributing traits. Wide range of variation was observed for seed size in the world chickpea germplasm collection (Upadhyaya, 2003). The two released chickpea varieties (BGD 103 and JAKI 9218) differing for seed traits were chosen for hybridization. The four (F2, F3, F4 and F5) generations were evaluated in the same year to estimate the extent of genetic variability generated, heritability and intra and inter generation correlation for seed traits and seed yield. Estimation of these parameters in different generations helps to understand the generation in which effective selection can be achieved for the trait.
A bold seeded desi chickpea variety BGD 103 (>30g/ 100 seed weight) was crossed with JAKI 9218. The cross was generated during post rainy season 2014-15 and the F1 was advanced during rainy season 2015-16. True F1 plants were identified and F2 seeds harvested in bulk. Part of the F2 seeds was retained and remaining seeds were sown during post rainy season 2015-16. Each of the F2 plants was harvested separately to raise F3 progeny rows during post rainy season 2016-17. Ten plants in each of the F3 progenies were chosen randomly and harvested as F4 bulk. The F4 -generation was raised during post rainy season 2017-18. Randomly selected ten plants in each F4 progeny rows were harvested in bulk to produce F5 generation. In each of the generations, part of the seeds was retained and no selection was made for any traits. The populations comprised of 162 F­2 plants, 162 F3, F4 and F5 progeny rows were evaluated during post rainy season 2018-19.

The seeds of each generation were sown in a single row 2.5 m length by adopting augmented design with three blocks and two parents as check. The checks were repeated for three times in each block. Observations on yield contributing traits viz., number of pods per plant, number of seeds per plant, seed weight and grain yield per plant were recorded. The observations on individual plants in F2 and five randomly chosen plants in each progeny rows of other generations (F3, F4 and F5) were used to record observations on four quantitative characters. The data was subjected to statistical analyses. Mean, range, variance, coefficient of variance, standard deviation and correlation among the traits in each generations, inter-generation correlation and heritability by the regression method were estimated using Microsoft excel program.
Estimation of heritability and genetic correlation is the basis for assessing the efficiency of indirect selection for yield contributing traits as against direct selection for grain yield. These parameters vary with the advancement of segregating generations. They need to be estimated for each segregating generations separately. But, estimation of these parameters for each generation in different season is influenced by environmental factors. Therefore, in the present study all the four segregating generations (F2, F3, F4 and F5) were evaluated in the same season to avoid varied environmental effect on the expression of traits in different generations. The comparison of mean values for the traits under study in four segregating generations revealed higher values for number of pods per plant, seeds per plant and seed yield in F3 generation (Table 1). In general mean values for these traits increased from F2 to F3 generation and decreased in subsequent generations. On the other hand for seed weight, the mean values remained constant in early segregating generations. Similar report was made by Salimath and Patil (1990). They evaluated F3 and F4 generations in the same season and observed an increase of pods per plant in F4 when compared to F3 generation, whereas it remained constant for seed weight. Shivakumar et al., (2013) evaluated F2 and F3 generations in two different seasons (Rabi 2009-10 and 2010-11). They reported that there was no change in number of pods per plant and seeds per plant in F2 and F3 generations but the seed weight increased in F3 when compared to F2 generation. The contradictory results of present study and the study reported by Shivakumar et al., (2013) may be because they advanced only promising segregants from F2 to F3 and evaluation of two generations in two different seasons.

Table 1: Mean, Range and coefficient of variability for quantitative traits in F2. F3, F4 and F5 generation of chickpea.



Decision on early segregating population cannot be based on only mean values of the traits. Because, selection based on the mean value of the early segregating generations does not provide the range and distribution pattern within each population (Welsh, 1981). In populations rejected on their mean value, low frequency of high yielding individuals may be lost. Therefore, range of variation and coefficient of variation are the two parameters, which needs to be considered in assessing the early segregating generations.  The range of variation for pods per plant and seed yield showed an improvement in F3 over F2 (Table 2). With the advancement of generations, the number of progenies with lower value increased for all the traits and progenies with upper value decreased leading to reduction in range of variation. As result frequency distribution of all the traits was skewed towards higher value in F2 generation, normal distribution in F3 generation and in F4 and F5 generation the distribution was narrowed down to only few classes. The reduction in lines with upper values for these traits is expected as these are the quantitative traits and may be governed by dominance variance. The other reason may be, as there is no selection pressure is applied the low frequency of lines with higher values for these traits may be lost in subsequent generations. However, for seed weight the higher value remained constant in all the generations. Similar results were reported for seed weight by Salimath and Patil (1990). The contradicting reports were made by Shivakumar et al., (2013), wherein they rejected less productive lines and advanced only promising lines to F3 generation. The variability (CV) for all the traits decreased with the advancement of generation. This can be attributed to presence of dominance variance in governing these traits, which is decreased with increase in the homozygosity. The extent of variability is indicative of possibility of application of selection pressure on the population. However, effectiveness of selection on the performance of progenies in the subsequent generation depends on the heritability of the trait. The heritability values in all the four generations calculated by the regression method revealed seed weight to be a highly heritable trait, while seeds per plant and number of pods per plant were moderately heritable. The seed yield per plant showed least heritability in all the generations. With the advancement of generation the heritability decreased for seed weight, increased for number of pods per plant and number of seeds per plant, while remained low and constant for seed yield per plant (Table 3). Lupton and Whitehouse (1957) suggested that in self pollinated cereals, selection in the early generations should be restricted to traits which are highly heritable. This suggests that selection can be practiced for seed and pod traits in F3 and F4 generations. Bisen et al., (1985) suggested that selection for seed size bulk procedure proved to have advantage over other methods of selection aimed at the genetic improvement of chickpea for seed yield.

Table 2: Heritability (%) of quantitative traits in F2. F3, F4 and F5 generation of chickpea.



Table 3: Correlation among different yield contributing traits in segregating generations of chickpea.



The association among the traits suggests that, in all the segregating generations (F2, F3, F4 and F5) seed yields were obtained with more number of pods per plant, seeds per plant and seed weight. Generally, indirect selection has only been successful where the heritability of the target trait (Seed yield) is very low and heritability of associated traits is high. Considering the variability and heritability of the traits in different generations, it could be concluded that, selection for seed weight in F2 generation, pod and seed number in subsequent F3 and F4 generation may contribute for genetic improvement for seed yield. Parents in the present study differed for seed weight and seed number. Seed weight is a critical trait, which showed positive and significant association with seed yield and other yield contributing traits in F2 generation. With the advancement of generation, its association with pod and seed number plant decreased and showed negative association with pods per plant in F5 and seeds per plant in F4 and F5 generations. The changes in the correlation between the traits from generation to generation may be due to high degree of segregation and genetic heterozygosity, which leads to breakdown and formation of new linkages (Kishore and Gupta, 2002). The high seed weight with high seed number is the desirable combination for yield improvement. Therefore simultaneous improvement of seed weight, seed number and seed yield could be achieved by selection for seed weight in F2 and seed number in subsequent generations.
 
The inter-generation correlation study showed significant association between F2-F3, F3-F4 and F4-F5 for seeds per plant and seed weight (Table 4). In general inter-generation correlation was low and insignificant for seed yield in all the generations. For other traits, it was high in F3-F4 and F4-F5 when compared to F2-F3. The extent of inter-generation correlation for seeds per plant and pods per plant increased with the advancement of generation. For both the traits correlation between F4 and F5 generations is more than the correlation between F3-F4 and F2-F3 generations. On the other hand high inter-generation correlation was observed for seed weight between F3 and F4, compared to F2-F4 and F4-F5 generations. High estimates of inter-generation correlations between F3-F4 and F4-F5 indicate that early generation selection for pods per plant, seeds per plant and seed weight should be preferably done in F3 or F4 generations. Rahman and Bahl (1986) also observed that, inter-generation correlation was high in F3 and F4 generation for seeds per plant and seed weight. Kumar and Bahl (1992) concluded that, high yielding lines could be obtained by selection for pod number and seed weight in four successive segregating generations (F2-F5). The high estimates of inter-generation correlation for number of seeds per plant and seed weight were recorded between F3 and F4 generation. Hence the simultaneous improvement of seed number and seed weight could be effective if selection for both the traits is done in early segregating generation.

Table 4: Inter-generation correlations between F2-F3, F2-F4, F2-F5, F3-F4 and F3-F5 for four yield contributing traits in chickpea.



Correlations between two generations apart (F2-F4, F3-F5) were lower than between consecutive generations. The correlations estimated for two generations apart that is between F2-F4 and F3-F5 was significant for seeds per plant and seed weight. Similarly the correlations between three generations apart was estimated (F2-F5) and it was very least and non-significant for all the traits. The estimation of genetic and statistical parameters and also frequency distribution for pod and seed traits suggests that, improvement of seed yield through improved number and seed weight is possible by selection at early segregating generation. Wherein initially the lines with high seed weight should be selected then in subsequent generation, lines with higher seed number should be given emphasis.
 

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