Indian Journal of Agricultural Research

Heterosis and inbreeding depression (10) were studied in 28 crosses involving eight dillerse parents of lowland rice for grain yield and its component traits under normal (E1) and late (E2) planting situations. Highly significant and positive heterosis for grain yield was observed in 15 and 9 crosses under E1 and E2, respectively. Among the different characters grain yield/plant recorded highest heterosis (97.0%) folloWed by biolcigical yield/plant (84.4%), no. of panicles/plant (84.0%) and no. of filled grains/panicle (81.0%) under normal planting. Similar magnitude of heterosis was observed for grain yield/plant under late planting also. In most of the crosses high heterosis for grain yield and its components was invariably accompanied by high inbreeding depression in F₂ generation. Under normal planting no, of panicles/plant exhibited highest 10 (56.8%) followed by grain yield/plant (54.5%) and biological yield/plant (52.3%). Among the different crosses four combinations viz., CN 1035–59/CN 718-8-21-10, Gayatri/Lunisree, Gayatri/Manoharsali and Lunisree/OR 1334-8 which shoWed significant positive heterosis for grain yield and some of its components under normal and late planting situations are suggested for commercial exploitation to improve grain yield in lowland rice.