Combining ability analysis for yield in hybrids of new plant type lines and indica varieties of rice (Oryza sativa L.)

The present investigation in rice was undertaken to study the combining ability of experimental hybridsthrough a line x tester mating designfor single plant yield and their attributing traits in Madurai. Nine new plant type linesviz., IR 71700-247-1-1-2, IR 72158-11-5-2-3, IR 72165-63-2-3-3, IR 72981-92-1-1-2-2, IR 72985-65-3-1, IR 73896-51-2-1-3, IR 73907-53-3-2-2, IR 73935-51-1-3-1 and IR 75282-10-3-3-2 and four indica varieties, namely, ADT 45, ASD 16, IR 72 and MDU 5, as testers and their hybrids were studied for ten characters namely days to 50% flowering, plant height, number of productive tillers plant-1, panicle length, number of grains panicle-1, spikelet fertility, 100 grain weight, leaf area index, harvest index and single plant yield. The hybrids exhibited significant variation among themselves for the ten traits studied. The LxT analysis revealed the importance of dominance gene action for all the traits except days to 50 per cent flowering and harvest index. Heterosis breeding or hybridization followed by selection in later generations was suggested for the improvement of these traits. Evaluation of parents based on per se and gcaeffects revealed that the following two lines IR 72985-65-3-1 and IR 73896-51-2-1-3 and the tester ASD 16 were the best and crosses involving them would result in improvement of yield.