Combining ability and heterosis in F1 and F2 diallel crosses of rice
2002
de Leon, J.C. (Philippine Rice Research Inst., Munoz, Nueva Ecija (Philippines)) Sasahara, T.
Diallel crosses of nine indica and japonica varieties of rice (Oryza sativa L.) were evaluated in the F1 and F2 generations during the 1999 and 2000 cropping seasons in Japan, respectively, to study combining ability and heterosis for yield and its component traits. General combining ability and specific combining ability were significant for yield per plant, panicle number, panicle length, spikelet number per panicle, filled spikelet number, and 100-seed weight. This indicated that both additive and non-additive types of gene action were important in the inheritance of these characters. Further analysis, however, revealed that specific combining ability variance was more predominant for yield, filled spikelet number and 100-seed weight. Combining ability effects in 1999 were highly and significantly correlated with estimates in the 2000 experiment for yield, panicle number, panicle length, and spikelet number. This suggested the repeatability of genetic effects in the F1 and F2 generations, although coefficients of determination were higher for the general combining ability effects of the parents. Results of heterosis analysis demonstrated the superiority of Indica x japonica crosses over inbred cultivars and intervarietal hybrids
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