Grain Characteristics and Inheritance of Two Split-Hull Mutants in Rice

Abstract

Two split-hull mutants were induced a) by the treatment of chemical mutagen, N-methyl-N-nitrosourea (MNU), in the fertilized egg cells of Hwasunchal and b) in the progeny crossed between Stay-green and Indica-like mutant lines. This study was carried out to investigate some grain characteristics of the mutant lines and to elucidate the inheritance mode of the split-hull trait. In the mutant line 74723, hull splitting was initiated about 15 days after flowering (DAF) and the percentage of split hull was 30~40%, which were not affected by temperatures and nitrogen levels. The hull-splitting was mainly caused by the relatively smaller girth of hull compared to the size of brown rice. The split-hull of the line 74723 was found to be controlled by a single recessive gene, which was tentatively designated as sph(t). In the other mutant line 16537, hull-splitting was initiated about 15 DAF in the field, which was significantly earlier in greenhouse. The ratio of split-hull in 16537 was over 95% on the average with little variation. The split-hull was caused by relatively larger brown rice than the hull girth covering it. Split-hull trait of the line 16537 was segregated in a quantitative fashion in F2 populations, indicating that the trait was controlled by polygenes. Broad-sense heritabilities in F2's of the trait were over 93%.