Department of Genetics and Plant Breeding, University of Agricultural Sciences, Dharwad,580005, Karnataka, India
Author
Correspondence author
Legume Genomics and Genetics, 2013, Vol. 4, No. 3 doi: 10.5376/lgg.2013.04.0003
Received: 11 Jul., 2013 Accepted: 17 Jul., 2013 Published: 19 Jul., 2013
Shivakumar et al., 2013, Assesment of Variability and Identification of Transgressive Segregants for Yield and Yield Component Traits in Early Segregating Generations of Chickpea, Legume Genomics and Genetics, Vol.4, No.3 22-26 (doi: 10.5376/lgg. 2013.04.0003)
In order to compute the genetic variability, heritability and genetic advance an investigation was carried out with 575 plants of F2 population and F2 derived F3 progenies from the cross between ICC 13124 and WR315 of chickpea (Cicer arietinum L.). The genotype ICC 13124 is tolerant to drought but susceptible to wilt, while, WR 315 is resistant to wilt and relatively less tolerant to drought. Considerably high variability was observed in 575 plants of F2 and F2-3 progenies. The phenotypic variance was higher than the corresponding genotypic variance for all the characters. Environmental influence was very meager in expression of most of the traits which is evident from narrow difference between Genotypic Coefficient of variation (GCV) and Phenotypic Coefficient of Variation (PCV) estimates. Heritability estimates in broad sense was high for all the characters under study in both F2 and F3 coupled with high genetic advance as per cent over mean indicated the presence of additive gene action for these traits. The crosses had thrown a good number of transgressive segregants over better parent for seed yield per plant. More number of transgressive segregants was found for number of seeds per plant followed by number of pods per plant and yield per plant. A track on these transgressive segregants should be maintained and forwarded to further generation till they reach nearly homozygous condition. Most promising one can be used in further breeding programme.
Chickpea (Cicer arietinum L.) is the third leading grain legume in the world and first in the South Asia. Ninety two per cent of the area and 89% of the production of grain are concentrated in semi-arid tropics. Its range of cultivation extends from the Mediterranean basin to the Indian subcontinent and southward of Ethiopia and the East African highlands.
In a highly self-pollinated crop like chickpea, the breeding strategy for varietal development generally involves selection of potential genotypes from the existing germplasm, utilizing them in the hybridization programme and isolation of superior genotypes in the segregating population. This necessitates a thorough knowledge of genetic variability, heritability and the genetic advance that can be achieved through selection. The objective of this study is to evaluate 575 plants of F2 and F2 derived F3 progenies for genetic variability, heritability, genetic advance and identification of superior/transgressive segregants.
Results and Discussion
The mean performance of two parents for eight quantitative traits suggested that variability was not observed for primary, secondary branches and seeds per pod. However, they were diverse in plant height, pods per plant, seeds per pod, seeds per plant and seed weight (Table 1). For all these traits, ICC 13124 was found to be superior to WR 315 except for seeds per pod. However, the diversity of these two parents for important traits fully justified their selection for generating the breeding material.
Table 1 Mean performance and range for seed yield per plant and its traits in F2 and F3 segregating populations of the cross ICC-13124 and WR-315 in chickpea |
The mean values for the six traits either remained equal in the F2 and F3 generations. Salimath and Patil, 1990 also observed equal mean values in F3 and F4 generation. The mean performance in respect of yield per plant and its component traits were same in both F2 and F3 of the cross. F2 was advanced to F3 by selecting the promising segregants in F2 and less productive plants were rejected. Consequently, the selection of promising plants has maintained the mean performance of these traits in F3 generation; clearly indicate additive effect may be governing the expression of these traits as it is additive variance, which is fixable (Falconer, 1960). Bicer and Dogan, 2008 reported that expression of traits such as plant height, seeds per plant, pods per plant and seed weight was governed by additive gene effect (Table 1).
The range of variation was high for plant height, number of primary branches, number of pods per plant, number of seeds per plant, seeds per pod, test weight and seed yield per plant in F2 and F3 (Table 1) however, F2 recorded wider range than F3 generation for all the characters. Overall, there is high amount of variation among the F2 and F3 might be due to diversity among parental genotypes. Similar results were recorded in F2 and F3 generation of cowpea by Salimath et al., 2007. It is seen that the range of expression has narrowed down in F3 for productivity and its component traits in both generation (Table 1). However, the upper value of the range is almost maintained except for seed yield in which case it has slightly declined, which is expected because yield is a quantitative character.
The extent of variability as measured by GCV and PCV also gave relative amount of variation in different characters (Table 2). A narrow difference between PCV and GCV indicated the negligible influence of extraneous factor on the trait. Moderate coefficients of variation for plant height and for number of primary branches were observed in both F2 and F3 which is in agreement with the results of Hasan et al., 2008. High genetic and phenotypic coefficients were observed for secondary branches by Malik et al., 2009 and Sharma and saini, 2010. Number of pods per plant recorded high variability in both F2 and F3. Similar observations of high variability were noticed by Hasan et al., 2008 and Ali et al., 2011. Both parents differed for seeds per pod which was reflected by high GCV and PCV in both F2 and F3 generation and similar results observed by Wahid and Ahmed, 1999 for seeds per pod. Contrasting results were reported by Hasan et al., 2008. Highest coefficient of variation for seeds per plant noticed in the present study was in conformant with Tripathi, 1998. Moderate to high coefficients of variation for 100 seed weight and high variation for seed yield per plant were recorded in both generation, whose results were in accordance with the findings of Vijayalakshmi et al., 2000 and Singh et al., 2004.
Table 2 Estimates of genetic parameters for eight quantitative characters in F2 and F3 segregating populations of the cross ICC-13124 and WR-315 in chickpea |
Comparison of performance of F3 with F2 revealed a considerable reduction in variance in F3 for important character like seed yield and other characters due to reduction in heterozygosity as compared to F2. The heritability in a broader perspective is the proportion of genotypic variability to the total variability. Heritability estimates in the broad sense alone is not a true indicator of effectiveness of selection for the trait since, it is restricted by their interactions with the environment. Hence, heritability values considered along with predicted genetic gain increases the reliability of the parameter as a tool in selection programme. Heritability and genetic advance over mean estimates were presented in Table 2.
Plant height showed high heritability coupled with high GAM in both F2 and F3 (Babar et al., 2008 and Ali et al., 2011). High heritability coupled with high GAM was noticed for both primary and secondary branches, this was in accordance with findings of Kampli et al., 2002 and Hasan et al., 2008. High heritability coupled with high Genetic Advance over Mean (GAM) was exhibited by pods per plant in both F2 and F3 (Dwevedi and Gaibriyal, 2009, Sharma and saini, 2010; Ali et al., 2011). For another important yield component trait, number of seeds per plant recorded high heritability and high Genetic Advance over Mean (GAM) which is in accordance with findings of Tripathi, 1998 and Ali et al., 2011.
High estimates of heritability along with high Genetic Advance over Mean (GAM) were noticed for 100 seed weight and seed yield per plant in both F2 and F3, this was in line with the findings of earlier workers Babar et al., 2008 and Sharma and saini, 2010. The comparison of these two estimates made in this study revealed that seed yield per plant and number of seeds per plant had high heritability estimates coupled with high genetic advance in both F2 and F3 indicate the substantial contribution of additive genetic variance in the expression of these characters. From this, it can be inferred that the selection criteria based on seed yield per plant and number of pods per plant will be useful for the improvement of seed yield in chickpea.
The crosses had thrown a good number of transgressive segregates over better parent for seed yield per plant (Table 3). More number of transgressive segregants were found for number of seeds per plant followed by number of pods per plant and yield per plant. This is in accordance with findings of Yadav et al (2003). Least number of transgressive segregants were found for test weight in F2 population and F3 progenies which may be due to very high seed weight of better parent ICC 13124. Transgressive segregant in the F2 might have arised due to dominance and dominance interactions in addition to additive×additive interaction which is fixable. Due to recombination of genes with positive effects are responsible for the production of more transgressive segregates in the F3 generation. The findings revealed that the parents involved in the study differed for many genes which resulted in creating large amount of genetic variability for yield and yield components in segregating generation. This suggests the scope of this material and the parents in future breeding programme. A track on this superior and transgressive segregants obtained should be maintained and forwarded to further generation till they reach nearly homozygous condition.
Table 3 Frequency of transgressive segregants for yield components in F2 and F3 segregating populations of the cross ICC-13124 and WR-315 in chickpea |
Material and Methods
The material for the present study was generated in the Botany garden, Department of Genetics and Plant Breeding, College of Agriculture, University of Agricultural Sciences, Dharwad, Karnataka, India. Dharwad is situated at 150°26’N latitude and 70°26’E longitude at an altitude of 678 m above mean sea level. The experimental material was developed by involving two genetically diverse germplasm lines viz. ICC 13124 and WR 315. The variety BGD-103 is considered as a local check to evaluate F2 and F3 generation. F2 generation was raised in rabi 2009-2010, while, F3 raised in rabi 2010-2011. The spacing between rows and within the row was 30 and 20 cm respectively. The crop was raised under irrigated conditions.
From F2 575 plants were randomly selected and observation on eight quantitative characters., viz. plant height (PH), primary branches per plant (PB), secondary branches per plant (SB), number of pods per plant (N0P), seeds per pod (SPPO), number of seeds per plant (NOS), test weight (TW) and seed yield per plant (SY) was recorded. Analysis of variance for all characters was carried out following Steel and Torrie (1997). The genotypic and phenotypic coefficients of variation were calculated according to Burton and Devane (1953). Heritability in broad sense was estimated by following Hanson et al (1956) and expressed as percentage. The extent of genetic advance that can be expected with five per cent selection intensity was calculated following Robinson et al (1949).
Authors' contributions
SMS carried out the overall experiment and drafted the manuscript. SPM and SO supervised the experiment as chairman and member of advisory committee. SSB was responsible for technical editing and final preparation of manuscript. TPO involved in collection of data and statistical analysis.
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