Studies on the genetic basis of heterosis and inbreeding depression for yield and yield attributing characters in rice (Oryza sativa L.)

Heterosis studies in rice were carried out on eighteen characters against two crosses (Cross I: Mashuri × Bhutmuri and Cross II: IR36 × Bhutmuri) at Instructional Farm, Jaguli, BCKV, West Bengal. Heterosis of F1 hybrids over mid parent and better parent varied from character to characters in the two crosses. Significant positive heterosis was observed for number of tillers per plant and number of panicles per plant in both the crosses. Highest inbreeding depression was observed for number of secondary branches per panicle and lowest for straw weight in Cross I. While highest inbreeding depression was observed for tillers per plant and lowest for grain L/B ratio in Cross II. Secondary branches per panicle in Cross I and number of tillers per plant in Cross II recorded high level of heterosis and inbreeding depression. Number of panicles per plant in Cross I and harvest index in Cross II showed high level of heterosis and low level of inbreeding depression which indicated the presence of both additive and non-additive gene effects for these characters. Above studies suggested that for crop improvement it would be desirable to follow different selection methods / breeding methods according to the gene action that controls the yield and different yield attributing characters.