Fine mapping of a fertility restoring gene for a new CMS hybrid rice system

The Fujian Abortion cytoplasmic male sterility (CMS-FA) system, a new type of sporophytic CMS system in indica rice (Oryza sativa L.), was developed using the cytoplasm and the corresponding fertility-restoring gene from a wild rice (O. rufipogon L.), which originated from Fujian Province, China. Previous studies in combination with several years of production practice demonstrated that CMS-FA hybrid rice was superior to CMS-WA hybrid rice, a prevailing hybrid rice worldwide, and that the male fertility restoration was controlled by a pair of dominant alleles. We tentatively designated the fertility restoration gene as Rf(fa). The analysis of the polymorphism between the fertile and sterile pool DNAs from a mapping segregation population (BC1F1) indicated that Rf(fa) was located on rice chromosome 10. We further delimited the Rf(fa) locus to a 121.1-kb region flanked by RM6100 and MM2023, which were approximately 0.26 cM and 0.18 cM away from Rf(fa), respectively, by simple sequence repeat molecular marker linkage genetic analysis. These results would facilitate the map-based cloning of Rf(fa), the elucidation of a novel molecular mechanism underlying cytoplasm–nucleus interaction in the CMS-FA system, and the production application of this hybrid rice.