Heterosis and Combining Ability Studies for yield and Productivity Traits in Rice: A Review

A review of work done was undertaken for accessing the extent of heterosis, general and specific combining ability for yield and productivity traits in rice. Identification of genetically superior parents is an important prerequisite in for the development of hybrids in rice. The combining ability analysis has been the efficient tool in choosing the desirable parents for hybridization programmes. It provides an empirical summary of complex observations and makes it possible to classify the parental lines in terms of superiority in hybrid combinations and the gene action involved in the inheritance of different traits. In majority of the experiments high specific combining ability (SCA) variances than general combining ability (GCA) variances for most of the traits were reported which indicate the predominance of non-additive gene action in the inheritance of these traits. However, in many other experiments the significance of GCA and SCA variances were also reported, and thus the equal importance of both additive and non-additive genetic components have been described. The researchers also found some correspondence between good general combiners and per se performance for some of the traits. Therefore, analysis of combining ability has been the most important and efficient tool in selecting the desirable parents for a hybridization programme. This review will help in understanding the exciting opportunities offered by heterosis, combining ability and gene action studies in rice.