Analysis of combining ability status among parents and hybrids in rice (Oryza sativa L.)

Abstract

The development and use of hybrid rice varieties on commercial scale utilizing the cytoplasmic male sterility (CMS)-fertility restoration system has proved to be one of the milestones in the history of rice improvement. The hybrid rice technology, now in operation in nearly 20 countries, aims at further research and development efforts with respect to cytoplasmic diversification, and yield increment through higher exploitable heterosis levels. Combining ability test is one of the several biometrical models being routinely used to study the genetic basis of heterosis. With a few exceptions all the studies showed significant general combining ability (gea) and specific combining ability (sea) effects for yield and/or yield components indicating role of both additive and non-additive gene action. Relative proportion of gea and sea variances were found to vary in different studies. Reports on analysis of combining ability status of parents in relation to that of hybrids as well as frequency of crosses with performance exceeding that of better parent in relation to gea effect of parents are limited in literature. An attempt has been made here to analyze the results obtained through combining ability studies in relation to the performance of hybrids and to provide valid explanations for the same.