EFFECT OF GAMMA IRRADIATION ON VARIATION IN SEGREGATING GENERATIONS OF F2 SEEDS OF RICE

Abstract

The F2 seeds of two rice crosses, Himalaya 1 x Phul Patas 72 and Himalaya 1 x China 988, were irradiated with 25 kR gamma-rays. The mean values of F2Ml generation decreased as compared to F2 for plant height, spikelet fertility and grain yield in both the crosses, and for panicle length and 100-grain weight only in the cross Himalaya 1 X China 988. On the other hand, mean values in the F3M2 generation for spikelet fertility and grain yield incre.ased in both crosses as compared to F3. However, the variance of F3M2 generations did not differ significantly from that of F3 generation in both the crosses for the characters studied, except for grain yield in the cross Himalaya 1 x China 988. Estimates of heritability and genetic advance in F3M2 were lower than in the corresponding F3 for all the traits in the cross Himalaya 1 x Phul Patas 72, except for plant height and 100- grain weight. However, the estimates of heritability and genetic advance in the F3M2 generation were higher than in F3 generation for all characters, except 100-grain weight and grain yield in the cross Himalaya 1 X China 988. The study also revealed that irradiation has differential effect on the same character depending on the genetic background of the test/segregating material.