Combining ability in radiation-induced mutants of aromatic rice

Combining ability for different quantitative characters in aromatic rice was studied following diallel analysis of 15 hybrids which were derived by crossing five morphologically distinct true-breeding mutants (Mut I to Mut 5), induced by gamma- irradiation and their mother variety Gobindabhog. Both additive and non-additive genetic components were important for plant height, days to flower, panicle length and weight, primary branches per panicle, spikelet fertility, test weight, harvest index, and grain yield with the preponderance of non-additive component for plant height, panicle weight, and grain yield. Flag leaf area, secondary branches per panicle, spikelets per panicle, and grains per panicle were governed by additive gene effect, while non-additive gene effect was responsible for panicle per plant and biomass yield per plant. Estimates of general combining ability effects revealed that Mut 5 was the best combiner for the majority of the characters followed by Mut 4. Radiation-induced changes in combining ability effects were apparent. Crosses which showed high specific combining ability effects had at least one parent with overall high general combining ability effects.