Studies on the effect of gamma rays in inducing grain number mutants in M2 and M3 generations in rice

The extent of induced variability in the number of grains per panicle as effected by 60Co-gamma rays at exposures of 10, 20 and 30 kR was studied in detail. Both in M2 and M3, the treated population showed a significant reduction in mean number of grains compared to control. The seven M1 panicle categories studied separately showed no significant variation either in M2 or in M3. Studies on the phenotypic frequency distribution of mutants showed a bidirectional shift compared to control. The maximum frequency of positive mutants was noticed in 30 kR both in M2 and M3. The seven M1 panicle categories showed no significant differences for the distribution of both negative and positive mutants either in M2 or in M3. The data clearly showed that genetic improvement by induced mutation is effective in the case of this yield attributing character. (author)