Heterosis and genetic studies on yield and associated physiological traits in rice (Oryza sativa L.)

Studies indicated that the amount of heterosis for leaf area index (LAI) at tillering stage, crop growth rate (CGR) from tillering to heading, harvest index, 100-grain weight and grain yield plant-1 was high and the inheritance of LAI, CGR net assimilation rate (NAR), harvest index (HI), days to 50% flowering, productive tillers plant-1, filled grains panicle-1 and grain yield plant-1 were predominantly under the control of nonadditive gene action. Whereas, 100-grain weight was largely governed by additive gene action. The parents IR 20 for LAI, RDR 763 for LAI, NAR and productive tillers plant-1 and Lunisree for CGR, HI, Biological yield and 100-grain weight were identified as good general combiners. The per se performance of the parents was found to be good indicator of their general combining ability. The best specific crosses with high SCA effects mostly involved parents with high x low or low x low GCA effects, hence heterosis breeding would be more rewarding to achieve another quantum jump in rice yields through exploitation of physiological traits.