Studies on genetic nature of harvest index in early varieties of rice

摘要

Genetic nature of harvest index in rice was studied through analysis of combining ability and stability of performance of 12 early-maturing varieties. In a 12-parent half-diallel analysis of parents and hybrids, the significance of general (gea) andspecific combining ability (sca) effect indicated the importance of both additive and nonadditive gene actions in inheritance of the character. Six varieties viz. OR 165-18-8, Sarathi, Suphala, CR 143-2-2, IR 36 and Keshari with high gea exhibited stability of performance under multi-environmental tests and they entered more frequently into heterotic hybrids. Hybrids with high harvest index exhibited high positive sea and midparent heterosis. The significance of sea in some of the hybrids indicated theimportance of nonadditive gene action. High-high, high-low and low-low parental combinations among 35 heterotic hybrids were 15,17 and 3 for parental mean and 14,18 and 3 for gea, respectively, thus indicating the importance of genetic diversity of theparents for realising heterosis. Heterotic hybrids for grain yield exhibited significantly high heterosis for harvest index. Hybrids exhibiting high heterosis with high-high gea combinations for both the traits considered to be potential for isolation ofpure lines through recombination breeding.