Inheritance of the fertility restoration and genotyping of rice lines at the restoring fertility (Rf) loci using molecular markers

The combination of cytoplasmic male sterility (CMS) in one parent and a restorer gene (Rf) to restore fertility in another are indispensable for the development of hybrid varieties. To genotype rice lines at the restoring fertility (Rf) loci, 38 lines were crossed with a sterile tester (rfrf) line. Pollen fertility test was performed to identify sterile and fertile F1 hybrids. Seven lines were identified as restorer lines. Then these F1 hybrids were self-pollinated to obtain F2 seeds, and at flowering stage pollen fertility test was performed to identify sterile and fertile individuals. Bulked segregant analysis (BSA) in F2 showed that fertility in rice WA system is controlled by more than two loci, one on the short arm of chromosome 1, one on the short arm of chromosome 10, one on the long arm of chromosome 10 and an unknown Rf gene in the rice genome. Results also show that lines IR28, Amol1 and Amol2 carry Rf4 gene linked with SSR marker RM171 on the long arm of chromosome 10, lines IR36 and IR60966 carry Rf3 gene linked with SSR marker RM1 on the short arm of chromosome 1, line IR62030 carries Rf5 gene on the short arm of chromosome 10, and finally line IR24 carries Rf4 gene on the long arm of chromosome 10 and an unknown Rf gene, respectively. The results suggested the use of the method deployed here to identify restorer lines and also allelic location of fertility restoration genes in rice lines.