Identification and fine mapping of a fertility restorer gene for wild abortive cytoplasmic male sterility in the elite indica rice non-restorer line 9311

Abstract

The wild abortive (WA)-type cytoplasmic male sterility (CMS) derived from the wild rice species Oryza rufipogon Griff. is used widely in three-line indica hybrids. The identification and mapping of restorer of fertility (Rf) genes aided in the development of WA-type hybrids. Here we report that testcross F1 plants from the WA-type CMS line and 9311 exhibited stainable pollen grains with no seed set, indicating that 9311 carries minor-effect Rfs for WA-type CMS. We developed an advanced backcross population consisting of plants harboring small regions of donor chromosomal segments from 9311 in the WA-TianfengA genetic background with moderate seed setting rates. Genetic analysis showed that the pollen fertility levels of the backcross individuals are governed by a single gene from 9311 that we named Rf19(t). By use of the RICE 40 K gene chip, three introduced segments were identified in the fertile lines, and a candidate region spanning 4.37–8.29 Mb on chromosome 1 was identified for Rf19(t). Finally, Rf19(t) was fine-mapped to a region of 90 kb between the DNA marker loci STS1-163 and STS1-183, in which eight ORFs were predicted. Also, using relative expression analyses, comparative sequence analyses and functional domain analyses, we identified LOC_Os01g10530 as the most likely candidate gene for Rf19(t). Furthermore, Rf19(t) was found to function in fertility restoration, most probably by regulating the degradation of mRNA transcribed from the mitochondrial gene WA352. These results increase our knowledge of fertility restoration in WA-type CMS lines and will facilitate the development of high-quality pairs of WA-type CMS and maintainer lines.