Precise Genetic Mapping of Rf18(t), A New Fertility Restorer Gene From ‘Nipponbare’ for Wild Abortive Cytoplasmic Male Sterility in Rice (Oryza Sativa L.)

Abstract Three-line hybrid rice obtained through cytoplasmic male sterility (CMS) has helped increase the yield of rice globally, and the wild abortive (WA)-type cytoplasm from wild rice (Oryza rufipogon Griff.) is used widely in three-line indica hybrids. The identification and mapping of the Restorer-of-fertility (Rf) genes in maintainer lines aided in uncovering the genetic basis of fertility restoration of WA-type CMS and the development of WA-type hybrids. In this study we identified a new Rf gene, Rf18(t), for WA-type CMS from the japonica maintainer line ‘Nipponbare’ using a chromosome segment substitution line (CSSL) population derived from a cross between the indica line 9311 and ‘Nipponbare’. Using a substitution mapping strategy, Rf18(t) was delimited to a 48-kb chromosomal region flanked by molecular marker loci ID01M28791 and ID01M28845 on chromosome 1. By comparative sequence analyses, we propose that LOC_Os01g71320 is the most likely candidate gene for Rf18(t), and it is predicted to encode hexokinase. Furthermore, Rf18(t) was found to function in fertility restoration probably by a posttranscriptional mechanism and its function is dependent on the genetic background of 9311. These results broaden our knowledge on the mechanism of fertility restoration of WA-type CMS lines and will facilitate the development of WA-type rice hybrids.