Partitioning of genetic variance for yield, yield components and sodicity tolerance in rice

In order to understand gene actions for sodicity tolerance, grain yield and its components in rice, six basic generations (P1, P2, F1, F2, BC1 and BC2) were evaluated in a target environment. Based on combining ability and heterosis studies, five hybrids viz., FL 478 / IR 64, BPT 5204 / IR 64, RNR 57979 / FL 478, TETEP / FL 478 and TETEP / BPT 5204 were selected to undertake generation means analysis. In selected crosses, using F1s as female parents and respective two parents (P1 and P2) as male parents, back crosses viz., BC1 (F1 / P1) and BC2 (F1 / P2) were effected. Thus, all six generations viz., P1, P2, F1, F2, BC1 and BC2 were built up in each five selected cross combinations. The 14 physio-morphological traits recorded were days to 50 percent flowering, plant height, number of productive tillers per plant, panicle length, number of filled grains per panicle, spikelet fertility percentage, 100-grain weight, single plant yield, dry root weight, dry shoot weight, root: shoot ratio, Na+: K+ ratio, chlorophyll content and proline content. Generation means analysis of the data revealed that all these traits exhibit significant non-allelic interactions and suggest that complex epistatic interactions are more important in controlling sodicity tolerance traits.