The inheritance of induced-mutant semidwarfing genes in rice

Inheritance of semidwarfism was studied in several mutant lines selected from an irradiated pdpulation of the cultivar Calrose. Seniidwarfisrn in the mutants D23, D24, D25, and D32, as in the mutants D7 and D66, is conditioned by single recessive genes. Mutants D23, 1)24, and D25 possess a sernidwarfing gene at one locus (sd4) and mutants D7 and D32 posse the semidwarflng gene at another locus (sd1). D24 is nonallelic to D7, and D66. D36 may possess a semidwarfing gene at an additional locus. Hence, at least three, nonallelic sernidwarfing genes (sd1 in D7, sd in D66, and sd4 in D24) have been induced in the cultivar Calrose. Genes sd1, sd2 and sd4 are inherited independently of each other and of the gene for glabrous leaf character. The sd4 gene demonstrates pleiotropic effects of small seed size and slightly earlier maturity. The degree of dominance for height at this locus was estimated to be h' = 0·49. The implications of these results for rice breeding are discussed.