A genome-wide analysis of wide compatibility in rice and the precise location of the S5 locus in ...
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A genome-wide analysis of wide compatibility in rice and the precise location of the S5 locus in the molecular map Liu K. D., J. Wang, H. B. Li, C. G. Xu, A. M. Liu, X. H. Li and Q. Zhang. 1997. Theor. Appl. Genet. 95:809-814. ABSTRACT The finding of wide compatibility varieties (WCVs), that are able to produce normal fertility hybrids when crossed both to indica and japonica rice, has allowed for the breaking of the fertility barrier between indica and japonica subspecies, and opened the possibility of developing inter-subspecific hybrids in rice breeding programs. It has often been observed, however, that there is considerable variation in fertility level of hybrids from the same WCV crossed to different varieties. A hypothesis for such variable fertility is that additional genes are involved in hybrid fertility besides the wide compatibility gene (WCG). To assess such a possibility, we performed a genome-wide analysis by assaying a large population from a three-way cross 02428/Nanjing 11//Balilla, using a total of 171 RFLP probes detecting 191 polymorphic loci distributed in the entire rice linkage map. Our analysis recovered 3 loci conferring significant effects on hybrid fertility. The major locus on chromosome 6 coincided in chromosomal location with the previously identified S5 locus, and the two minor loci, mapped to chromosomes 2 and 12 respectively, were apparently distinct from all the previously reported hybrid sterility genes. Interaction between the indica and japonica alleles at each of the loci caused a reduction in hybrid fertility. The joint effect of the two minor loci can lead to partial sterility even in the presence of the WCG. We also determined the location of the S5 locus on the molecular marker linkage map, which is approximately 1.0 cM from the RFLP locus R2349. This tight linkage will be useful for marker-aided transfer of the WCG in hybrid rice breeding and for map-based cloning. Key words Oryza sativa L., indica and japonica, hybrid sterility, mapping, rice breeding