Characterization and Fine Mapping of Hsph Controlling the Split Hull Character in Rice

A split-hull mutant, Hsph, was induced by treating with a chemical mutagen, N-methyl-N-nitrosourea(MNU), on the fertilized egg cells of a japonica rice cultivar Hwaseonchal. The hull of Hsph was split producing a chasm between lemma and palea during grain filling period. The mutant was phenotypically characterized and the gene was mapped in this study.

In the mutant, hull splitting initiated about 15 days after flowering (DAF). The percentage of split-hull grain was 40% on the average. Genetic segregation ratio of the F₂ populations derived from the crosses between Hsph with Hwaseonchal fitted to 3:1 ratio (wild type to split-hull type). This indicated that the split-hull trait was controlled by a recessive gene. To identify the Hsph gene controlling the split-hull trait in the mutant, genetic map was constructed with an F₂ population derived from the cross between Hsph and Milyang 23. The BSA and subsequent fine mapping revealed that Hsph was located in chromosome 4 between two markers, AL731593 and CS04p22774, flanking 154kb-length region that includes thirty ORFs. Sequencing analysis is in progress to isolate the gene Hsph.