Generation Mean Analysis of Yield and Yield Component Traits in Indian Mustard (Brassica juncea L. Czern. & Coss.)

Abstract

Understanding the genetic basis of seed yield and component traits is essential for developing efficient breeding strategies in Indian mustard (Brassica juncea L. Czern. & Coss.), where yield is governed by multiple genes and their interactions. The present study was undertaken to estimate the nature and magnitude of gene effects controlling seed yield and component traits in the cross PYR 2021-5 × PYR 2021-6 using generation mean analysis. Six basic generations (P1, P2, F1, F2, BC1 and BC2) were evaluated in a Compact Family Block Design with three replications during the Rabi 2025-26 season. Sixteen quantitative traits were recorded and genetic parameters were estimated using scaling tests, joint scaling analysis and Hayman's six-parameter model. Scaling tests revealed epistasis for all traits except siliqua length, while joint scaling analysis showed that fourteen traits required four-, five-, or six-parameter digenic interaction models, highlighting the importance of epistatic interactions in their inheritance. Significant additive and dominance effects were detected for most traits, with additive × additive and dominance × dominance interactions contributing substantially to their inheritance. Duplicate epistasis was observed for ten economically important traits, including seed yield per plant, thousand-seed weight and oil content, indicating complex inheritance. The findings demonstrate that both additive and non-additive gene effects govern yield and component traits, suggesting that delayed selection combined with pedigree breeding or recurrent selection may be effective for developing improved mustard genotypes.