Abstract

                                Analysis of variance of Compact Family Block Design revealed significant differences among the six cross families for twelve characters in E1 and E2 except for spikelet fertility in E1. Simple and joint scaling tests indicated presence of epistatic gene interactions and fitness of digenic interaction model for all the twelve characters in most of the six crosses in both conditions. Significance of epistasis was detected by either one or both type of scaling tests in irrigated and/or drought condition for all the characters across six crosses. In several instances, results indicated role of genotype x environment interactions in conditioning the epistasis for various characters in crosses. Across the six crosses, role of epistasis was comparatively more pronounced in drought condition as compared to irrigated condition, especially for DFF, PH, SF and HI. The nature and magnitude of gene effects and epistatic interactions for a character exhibited considerable variation across the six crosses and two environmental conditions. The considerable crosses exhibited positive and significant estimates of standard heterosis across sixteen characters in E 2. However, heterosis was comparatively higher for G/P in both conditions, for S/P in E1 and for PH and EBT in E2. The extremely diverse nature of parents involved in six cross combinations may have resulted in incompatible gene combinations or genetic architecture in crosses resulting into poor performance and lack of heterosis for most of the characters.

Key words : Rice, Drought, Metric traits, Gene action, Heterosis, Inbreeding depression