Mapping fertility-restoring genes of rice WA cytoplasmic male sterility using SSLP markers

Rice wild abortive (WA) type cytoplasmic male sterility (CMS) is commercially used for production of hybrid seeds in China. Two fertility restorer genes in the CMS-WA system were detected with SSLP markers in this study. An F 2 population consisting of 210 excessive sterile individuals from a cross between Zhenshan 97A and a strong restorer line IR24 was used for mapping of Rf4. The genetic distance from Rf4 locus to RM171 (OSR33) and RM228 on long arm of chromosome 10 was 3.7 cM and 3.4 cM, respectively, which were the two closest SSLP markers flanking the Rf4 locus. The two SSLP markers gave promise of application in molecular marker-assisted selection (MAS) for fertility restorer lines of the CMS-WA system. RM244, another SSLP marker on the short arm of chromosome 10, was found to be linked with a fertility restorer locus in an F 2 population consisting of 30 exces- sive sterile individuals from a cross between Zhenshan 97A and a weak restorer line IR64. The genetic relationship among fertility restorer genes Rf1, Rf4 and Rf5(t) for three rice CMS system is also discussed.