HETEROSIS AND INBREEDING DEPRESSION IN UPLAND RICE CROSSES

Abstract

Fl heterosis over midparent (MP) and beUer parent (BP) and F:z inbreeding depression (10) were studiedin8crossesof rice for grain yield/plantand its four componenttraits, i.e., plant height, effective tillers/plant, filled grains/panicle and lOGO-grain weight. Highly significant and positive heterosis for grain yield over MP and BP was expressed by four hybrids and, invariably followed by 10 in F:z. Such high grain yield heterosis was due to additive heterotic effect of one or more component traits. In all the cases, heterosis for number of effective tillers was observed to be the major contributor and number of filled grains/panicle to a lesser extent, to grain yield heterosis. High heterosis accompanied by high 10 for effective tilletslplant and filled grains/panicle indicate that nonadditive gene effects govern the inheritance of these traits. Since the hybrid vigour was not of retentive nature, as indicated by high 10 in F:z for grain yield, it can be exploited only in Fl.