Estimation of gene action and interaction for some quantitative characters in rice (Oryza sativa L.) by generation mean analysis

The present investigation was conducted to understand the genetic action for controlling the inheritance of some quantitative characters. The experimental materials consisted of three rice varieties, i.e., Mahsuri, Bhutmuri, IR36 and F₁F₂ and F₃ populations of Mahsurix Bhutmuri (Cross I) and IR36x Bhutmuri (Cross II). To conduct the generation mean analysis, the parents and their F₁ F₂ and F₃ populations were evaluated during June to October month of Kharif 2016 and Kharif 2017. Generation mean analysis was done for eighteen quantitative characters following the five parameter model. The Analysis of Variance revealed significant differences among the five generations for all the characters studied. The results of the scaling tests and joint scaling test revealed that the Simple additive-dominance model was inadequate for days to 50% flowering, days to maturity, number of panicles plant⁻¹, number of primary branches panicle⁻¹, number of secondary branches panicle⁻¹ in Cross I, while it was for plant height, number of tillers plant⁻¹, number of panicles plant⁻¹, number of grains panicle⁻¹, number of filled grains panicle⁻¹ and fertility % in Cross II. Hence, the present studies have revealed that epistasis as a basic mechanism that cannot be ignored. Thus, formulating breeding policies on only main gene effects i.e. additive and dominance could be misleading.