Abstract
Gene constitutions on heading time of 5 late matured mutants induced by radiation from Fujisaka-5 were analysed. Crossed F2 of mutant strains to the original variety and intercrossed F2 among mutant strains were cultured under natural field condition to observe their segregations on heading time. The ratio in segregation under long day conditions of F3 lines of FM2 x FM5 and FM3 X FM5 Were also observed. The results indicate that the two latest mutant strains FM5 and FM6, are induced by mutation of a major gene, that is highly sensitive to day-length and recessive to the original variety that is nonsensitive to day-length. The locus is, however, independently different of each other in two strains. Other mutant strains were seen to mutate in several genes which are weak in expression of characters, but their gene constitutions were not analyzed. All mutated strains were also seen to mutate on heading time in polygenes at the same time
