GENETIC-CONTROL OF SEEDLING TOLERANCE TO ALUMINUM TOXICITY IN RICE

An uncomplete diallel analysis was conducted for 56 F1 progenies deriv ed from 8 male x 7 female parents with differential Al tolerance based on root tolerance index (RTI) in a solution culture with Al concentra tion of 1 mM Al. Remarkable variation in RTI among the parents was obs erved after 6 weeks in culture. Significant (P < 0.001) general combin e ability (GCA) variance for both male and female parents and specific combine ability (SCA) variance were observed. The variance of GCA was much higher than that of SCA, indicating greater additive expression of the tolerant trait. Higher narrow-sense heritability (48%) was dete cted, indicating the possibility of a genetic gain in selection for Al tolerance based on RTI. The tolerant performance of F1 progenies appe ared to be influenced by the susceptible genotype. suggesting the inco nsistent dominance effect. The possible mechanisms of the apparent inc onsistent dominance was discussed in terms of the genetic background i n wheat. Two restore lines, Pedel and 02428, and one sterile variety, XieqinzaoA, were found to be high in the GCA effect and SCA variance i n this case. These genotypes may be useful in development of hybrid ri ce production on acid soils.