Fine Mapping of HWC2, a Complementary Hybrid Weakness Gene, and Haplotype Analysis Around the Locus in Rice

Abstract

Abstract Hybrid weakness is a reproductive barrier. In rice, the hybrid weakness caused by two complementary genes–– HWC1 and HWC2 ––has been surveyed extensively. However, their gene products and the molecular mechanism that causes hybrid weakness have remained unknown. We first performed fine mapping of HWC2 , narrowing down the area of interest to 19 kb. We thereby identified five candidate genes. Second, we performed haplotype analysis around the HWC2 locus of 33 cultivars. With 15 DNA markers examined, all the 13 Hwc2 - 1 carriers share the same haplotype for consecutive 14 DNA markers. As for hwc2 - 2 carriers, five out of 20 have the haplotypes relatively similar to those of Hwc2 - 1 carriers. However, the other haplotypes differ remarkably from them. These results are useful to identify the HWC2 gene and to study rice varietal differentiation.