Analysis of Combining Ability and Gene Action for Seed Yield and its Component Traits in Pigeonpea [Cajanus cajan (L.) Millspaugh]

The five females (Banas, GT 102, GT 103, GT 100 and GT 1) used as lines and four males (SKNP 1408, SKNP 1406, Vaishali and BDN 2004-01) used as testers  were crossed in Line ´ tester mating design to produce 20 F1’s under insect proof net house (to avoid outcrossing) at Pulse Research Station (PRS), Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Gujarat, during Kharif-2019. Thus, the 29 genotypes including 9 parents and 20F1’s were grown during kharif-2020.

The experimental material comprising of 29 entries including 9 parents and 20 crosses were raised in a Randomized Block Design with three replications. Each male and female lines were grown in a single row of 3.0 m length keeping an inter-row and intra-row distance of 60 cm and 20 cm respectively. Observations were recorded from five randomly chosen plants for each genotype in each replication for various characters, including number of branches per plant, number of pods per plant, length of the pods, number of seeds per pod, plant height, seed index, seed yield per plant, biological yield per plant, harvest index, total protein content and leaf area per plant. The data were compiled for analysis of the variance of different traits using the method suggested by Panse and Sukhatme (1978). Combining ability was analyzed as suggested by Kempthorne (1957). Correlation coefficients were calculated at both the genotypic (rg) and phenotypic (rp) levels as method described by Al-Jibouri  et al. (1958).

The analysis of variance presented in Table 1 outlines the variations observed among both parental lines and hybrids across 13 attributes assessed. Notably, the results unveiled significant mean squares attributed to genotypes across all traits, underscoring the ample genetic variability inherent in the studied materials. Furthermore, the mean sum of squares pertaining to parents versus hybrids exhibited significance across most attributes, with the exceptions being days to flowering, days to maturity and plant height. Following this, a pivotal aspect in any breeding programme entails the strategic selection of an appropriate breeding strategy to effectively harness the observed variability. This decision-making process heavily relies on discerning the type of gene action prevailing within the population concerning the traits targeted for genetic improvement, subsequent to the identification of suitable parent plants and prospective crosses (Cockerham 1961; Sprague 1966).



The results of an analysis of variance for combining ability for thirteen characters are presented in Table 2. The significance of mean squares attributed to various factors in the experimental study was notable across multiple traits, with exceptions noted for specific characteristics such as the number of branches per plant. Notably, testers exhibited significant influence on most traits, except for a few like the number of branches per plant, number of seeds per podand harvest index. Moreover, the interaction between lines and testers significantly impacted traits like the number of pods per plant, test weight, seed yield per plant, harvest indexand total protein content, underscoring the importance of hybrid combinations in determining specific combining abilities.



In terms of contribution, female lines displayed a higher mean square compared to testers for several traits including days to flowering, days to maturity, plant height, number of branches per plant, number of pods per plant, pod length, biological yield per plant, harvest index and total protein content. This indicates a predominant influence of female parents on these characteristics. Conversely, testers played a more prominent role in traits such as the number of seeds per pod, test weight, seed yield per plantand leaf area per plant, as reflected by their higher mean squares.

Furthermore, the interaction variances due to lines x testers were exceptionally significant for traits such as the number of pods per plant, test weight, seed yield per plant, harvest indexand total protein content. This underscores the importance of specific combining ability variances in the inheritance of significant traits, highlighting the complex interplay between parental lines and testers in hybrid performance. By elucidating the differential contributions of parental lines and testers to various traits and emphasizing the significance of their interaction in hybrid performance.

The ratio of σ²gca / σ²sca being more than unity was found for number of pods per plant, length of the pods, number of seeds per pod, seed index, seed yield per plant, biological yield per plant, harvest index and leaf area per plant, which indicates preponderance of additive gene action (Table 2). This is supported by Khorgade et al., (2000). While, the ratio of σ²gca / σ²sca being less than unity was observed for days to maturity, plant height, number of branches per plant and total protein content, which indicate preponderance of non-additive gene action. These results are in concordance with Baskaran and Muthiah (2007); Chandra et al. (2024). Therefore, for enhancing these traits, employing bi-parental mating followed by recurrent selection would prove fruitful in obtaining desirable recombinants. Given the simultaneous role played by additive and non-additive genetic effects in determining the inheritance of different characters, utilising both additive and non-additive genetic variances through biparental crosses and modified recurrent selection in population breeding may lead to greater genetic improvement.

The estimates of general combining ability effects of the parents for various characters are presented in Table 3. The parents viz. GT 102, Vaishali, GT 1 and BDN 2004-01 were found good general combiners for seed yield and its contributing traits like number of pods per plant, number of seeds per pod, test weight, harvest index and leaf area per plant. Banas, GT 102, SKNP 1408 and SKNP 1406 emerged as superior performers in terms of early flowering, evidenced by their markedly significant and negative general combining ability (GCA) effects. This observation underscores their potential for imparting early flowering characteristics to their progeny. Moreover, concerning days to maturity, a similar trend in GCA effects was observed specifically with parent GT 102. The minimum number of days to flowering and maturity is preferred to reduce the crop growth period. While, for days to flowering and days to maturity line GT 102 exhibited significant negative gca effect for both these traits. Therefore, these lines could be used in the synthesis of early maturing hybrids. Parents viz, GT 100, SKNP 1408, Vaishali and BDN 2004-01 are good combiners for plant height in desired direction. Banas and SKNP 1406 are good combiners for the number of branches per plant. GT 102 for number of pods per plant along with GT 1, Vaishali and BDN 2004-01 for number of pods per plant, number of seed per pod, test weight, harvest index and leaf area per plant, recorded as good combiners as they ultimately lead to increase of seed yield by producing superior hybrids. These results are in concordance with Chaudhary​ et al. (2016) and Soni and Patel (2016). While, for protein content, Banas, SKNP 1408 and Vaishali considered as good combiners to producing hybrids which contains good amount of protein, which is beneficial for reducing the Kwashiorkor disease. These results were supported by Soni and Patel (2016) and Patel et al. (2020) for total protein content.



Specific combining ability effect is a very important estimate for determining the potentiality of cross combination. The results of SCA effects of the hybrids for various characters are presented in Table 4. Out of the 20 cross combinations, GT 102 x SKNP 1408 and GT 103 x BDN 2004-01 were found to be positive and significant specific combiners for seed yield per plant. The results were found similar with work done by Patil et al. (2015), Soni and Patel (2016), Patel et al., (2020) and Kumar et al., (2001). While, none of the crosses exhibited negative and significant SCA effects for days to flowering, days to maturity and plant height. But some crosses exerted negative value of sca effect which indicates that they are average specific combiner. The results are in accordance with similar findings of Thiruvengadam and Muthiaha (2012) and Chaudhary  et al. (2016). Crosses viz., Banas × SKNP 1406, GT 1 x Vaishali and GT 100 x SKNP 1406 for branches per plant, GT 1 x BDN 2004-01, GT 100 x BDN 2004-01 and GT 103 x SKNP 1406 for number of pods per plant, GT 100 x Vaishali (0.68) and Banas x SKNP 1408 for test weight, GT 100 × SKNP 1406, GT 102 x SKNP 1408 and GT 1 x Vaishali for harvest index and GT 103 x SKNP 1408 for total protein content, exhibited positive and significant sca effect which reveals they are good specific combiner and further they used as potential variety. While, some crosses exhibited positive but non-significant value of sca effect for traits likes, pod length, number of seeds per pod, biological yield per plant and leaf area per plant, which indicates that they are average specific combiner and there is need to further utilized them with proper breeding methods for betterment of their combining ability. Soni and Patel (2016) and Patel et al. (2020) obtained similar result for above traits.



The phenotypic correlation represents the observable relationship between two traits, while the genotypic correlation reflects the inherent association that can enhance the genetic makeup of genotypes through selection for seed yield and its contributing traits. The estimate of genotypic and phenotypic correlation coefficients was presented in Table 5. The higher magnitude of genotypic correlation coefficients compared to phenotypic correlation coefficients for almost all studied traits suggested a strong inherent association between these characters, indicating minimal environmental influence on their expression. Seed yield per plant showed positive and significant correlation with number of pods per plant, pod length and number of seeds per pod at both genotypic and phenotypic levels. Therefore, more preference is given to entries which exhibits high value for above traits in future breeding programme. Similar results recorded by Vanniarajan et al., (2023).

The breeding programme for pigeonpea can leverage specific parent combinations and hybridizations to enhance seed yield per plant and other yield components. Seed yield per plant showed a positive and significant correlation with the number of pods per plant, pod length and the number of seeds per pod. Therefore, entries with high values for these traits should be prioritized in future breeding programs. Parents such as GT 1, GT 102, Vaishali and BDN 2004-01 exhibit significant general combiner effects, highlighting their potential for contributing to desirable traits. It’s recommended to initially select parents based on per se performance and general combining ability (GCA) effects, followed by recurrent selection to exploit both additive and non-additive gene actions simultaneously. While, Crosses viz., GT 102 x SKNP 1408 and GT 103 x BDN 2004-01 were found to be positive and significant specific combiners for seed yield per plant. Hence, these crosses were identified as potential for getting good transgressive segregants for seed yield per plant and its component traits and suggested for further evaluation in future breeding programme.

The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.

The authors declare that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript.