Epistasis and gene effects for phenology, yield and oil content in sesame revealed by joint-scaling and six-parameter analysis

An investigation was undertaken at the Instructional Farm, Barrister Thakur Chhedilal College of Agriculture and Research Station, Bilaspur, Chhattisgarh, India, a constituent college of Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India to elucidate the nature of gene action for yield and its component traits in sesame (Sesamum indicum L.) through generation mean analysis in five crosses, namely Thilarani × TKG 55, Thilarani × Phule til, Thilarani × PKDS 12, Thilarani × JTS 08 and Thilothamma × JTS 08. The adequacy of the additive-dominance model was tested using A, B, C and D scaling tests. Significant scale effects for most traits indicated the presence of non-allelic gene interactions, demonstrating that simple additive-dominance inheritance was insufficient to explain trait expression. Pronounced epistasis was observed for days to 50 % flowering and days to maturity particularly in Thilarani × TKG 55, Thilarani × PKDS 12 and Thilarani × JTS 08, while seed yield per plant showed strong gene interaction in all crosses except Thilothamma × JTS 08. Generation mean analysis using the six-parameter model (m, d, h, i, j, l) revealed that both additive and non-additive gene effects governed the inheritance of the studied characters. Dominance effects were generally higher than additive effects for traits such as number of capsules per plant, biological yield and seed yield, especially in Thilarani × PKDS 12 and Thilarani × JTS 08. Duplicate type epistasis predominated in most crosses, indicating dispersion of favorrable alleles, whereas complementary epistasis was observed in specific combinations such as Thilarani × Phule til and Thilothamma × JTS 08. Traits like capsule length, number of seeds per capsule, thousand seed weight and oil content exhibited appreciable additive effects in certain crosses, suggesting the presence of fixable genetic variance. Overall, the study indicates that yield and its components in sesame are governed by complex inheritance involving additive, dominance and epistatic gene effects, necessitating appropriate breeding strategies for the development of superior genotypes.