GENETIC-CONTROL OF AMYLOSE CONTENT IN SELECTED CROSSES OF INDICA RICE

Models of Pooni et al. (1992) were employed to investigate the genetic control of amylose content in 10 rice crosses produced by the pairwise crossing of five varieties representing almost the whole range of amylose levels from 0 to 28 per cent. Analyses of the first-degree statistics revealed an important role of the additive and the dominance effects in determining the genetic variability in all the crosses. Epistasis and cytoplasmic effects were also observed to contribute significantly to the variability among the generation means of most crosses. Dominance was generally towards the higher score and its effects were enhanced by a complementary dominance x dominance interaction in several sets of basic generations. The predominantly additive nature of the genetic variability was further revealed by the analyses of second-degree statistics. Component D was detected significant in all the crosses while components H-1 and H-2 were non-significant throughout. Significance of the covariance components F' and F'', however, showed indirectly that dominance contributed significantly to variability at the variance level. Higher levels of transgression and considerable increases in the phenotypic ranges displayed by the segregating generations of various crosses, also pointed to their potency for yielding superior recombinants with diverse levels of amylose.