MOLECULAR ANALYSIS OF THE INHERITANCE OF THE S-5 LOCUS, CONFERRING WIDE COMPATIBILITY IN INDICA-JAPONICA HYBRIDS OF RICE (ORYZA-SATIVA L)

RFLP analysis was conducted on a population derived from a three-way c ross to determine the location of the hybrid sterility locus, S-5, in relation to mapped molecular markers and to identify markers that woul d be useful for selection in breeding. S-5 is of interest to rice bree ders because it is associated with spikelet sterility of F-1 hybrids i n Indica/Japonica crosses. Identification of an S-5 allele which confe rs fertility in Indica/Japonica hybrids when introgressed into either the Indica or the Japonica parent has been reported. Varieties carryin g this S-5(n) allele are known as ''wide compatibility varieties (WCV) ''. Our data suggests that RFLP marker RG213 on chromosome 6 is closel y linked to the S-5 locus and can be efficiently used to identify wide compatibility (WC) lines. RG213 is a single-copy genomic clone that d etects three bands of different molecular weights in DNA from Japonica ('Akihikari') and Indica ('IR36') varieties and WC line ('Nekken 2'). We demonstrate that the three alleles detected by this marker could b e used to trace the inheritance of the ''wide compatible'' phenotype i n breeders' material.