Molecular tagging of Rf genes for the fertility restoration of WA-CMS system by bulk segregant analysis in rice

The process of screening for fertility restoration trait involves test crossing with a set of cytoplasmic male sterile (CMS) lines and evaluation of F-1 hybrids for pollen and spikelet fertility. In the present study, F-2 mapping population derived from a cross, APMS 6A x RP 5933-123 was utilized to map Rf genes. The F-2 population was also genetically analysed for pollen and spikelet fertility percentage. Chi-square (chi(2)) analysis to showed that the fertility restoration trait followed expected digenic ratio. By bulk segregant analysis (BSA) likely Rf genes containing regions were located on chromosome 10. The SSR markers viz.. RM304, RM258 located on chromosome 10 and RM23958 located on chromosome 9 showed clear polymorphism between two groups of fertile and sterile bulks. Based on BSA linkage analysis and F-2 population, pollen and spikelet fertility analysis along with molecular screening results of Rf linked markers, it is concluded that Rf4 gene located on chromosome 10 is playing major role and contributing to 90% of fertility restoration trait of newly derived restorer line RP5933 along with minor effect genes from chromosome 9. The findings may be useful for rice hybrid breeding.