Genetic components of variation for seed yield and its component traits in castor (Ricinus communis L.) through diallel analysis

The experimental material consisting of 101 entries comprised of ten parents and their 45 hybrids and 45 F2s developed through half diallel mating design and one standard check (GCH 7) were evaluated in a randomized block design with three replications. Numerical approach of diallel analysis was used to assess the nature and magnitude of gene action governing the expression of quantitative traits. The t2 values were found non-significant for all the characters in both the generations, which suggested that assumptions of diallel analysis are fulfilled. The overall results of genetic components of variances for seed yield and other characters revealed that the estimates of dominance component of genetic variance (D) were significant for days to 50% flowering of primary raceme, days to maturity of primary raceme, number of nodes up to primary raceme, length of primary raceme, effective length of primary raceme, number of capsules per plant, 100-seed weight, oil content and seed yield per plant in both F1 and F2 generations except for number of nodes up to primary raceme in F2 and oil content and seed yield per plant in F1 generation. The components of dominance effects (H1 and H2) were significant for all the characters in both the generations except for H2 in case of effective length of primary raceme in F2 and number of effective branches per plant in F1 generation suggesting the prevalence of both these dominance components in the inheritance of all these characters. This suggested the involvement of dominance gene action in the inheritance of these traits. The ratio of total number of dominant to recessive genes (KD/KR) in the parents was greater than one for all the characters in both F1 and F2 generations except for oil content, which indicated unequal frequency of recessive and dominant genes with an excess of dominant genes in the parents for these traits. High narrow sense heritability estimates were observed for effective length of primary raceme and 100-seed weight in F1 generation, moderate heritability was noticed for number of nodes up to primary raceme, length of primary raceme, number of effective branches per plant, number of capsules on primary raceme and oil content in F1 generation, Remaining characters possessed low estimates of narrow sense heritability.