SSR Marker-based Mapping Of CMS-WA Fertility Restoring Genes In A Restorer Line Of Rice

Cytoplasmic male sterility (CMS) and its restoration are bases for the breeding and commercial application of three-line hybrid rice. Wild abortive CMS (CMS-WA) was firstly used in the commercial production of hybrid rice and has always been most extensively applied. In the present study, 704 lines of the test-cross population Zhenshan 97A/(Zhenshan 97B/Milyang 46)F6 were established for mapping restorer genes for CMS-WA. SSR marker-based genetic linkage map was constructed to cover chromosome 10 and the short arms of chromosomes 1 and 11, in which genes for CMS fertility restoration have been reported.With the original population consisting of 704 lines, four QTLs for CMS-WA fertility restoration were detected, among which Rff on the long arm of chromosome 10 displayed a major effect, Rfi on the short arm of chromosome 1 had a considerable effect, and qRflO and qRfll in the pericentromeric regions of chromosomes 10 and 11, respectively, had minor effects. Significant digenic interaction was also detected between Rff and Rfi, showing partially duplicate action.To determine the effect of each restorer gene in the absence of Rf4 or Rfi, the population was classified into two subpopulations based on genotypes at RM6100 and RM1195 which were closely linked to Rf4 and Rfi, respectively. In one subpopulations, the genotype at the given marker locus was maternal homozygotes and the corresponding fertility restoring allele was absent, and the other subpopulations had heterozygotes at the given marker locus indicating the presence of the corresponding fertility restoring allele. Each of the four subpopulations was used to detect QTLs for fertility restoration. R/4 showed major effects for fertility restoration in the absence and presence of Rfi. The other three QTLs had effects for fertility restoration in the absence of Rf4, among which Rfi had the largest effect. It was also found that Rfi, qRflO and qRfll contributed to higher spikelet fertility in the presence of Rf4, whereas qRflO and qRfll showed little effect in the presence of both Rfi and Rf4.