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

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 WATianfeng A 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 m RNA 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 WAtype CMS and maintainer lines.

Genetic Analysis and Mapping of Genes Involved in Fertility of Pingxiang Dominant Genic Male Sterile Rice

Pingxiang-dominant genic male sterile rice （PDGMSR） was the first dominant genic male sterile mutant identified in rice （Oryza sativa L.）, and the corresponding dominant genic male sterile gene was designated as Ms-p. The fertility of PDGMSR can be restored by introduction of a dominant epistatic fertility restoring gene in some rice varieties. In the present study, E823, an indica inbred rice variety, restored the fertility of PDGMSR, and the genetic pattern was found to be consistent with a dominant epistatic model, therefore, the dominant epistatic fertility restorer gene was designated as Rfe. The F2 population from the cross of PDGMSR/E823 was developed to map gene Rfe. The F2 plants with the genotypes Ms-pMs-pRferfe or Ms-pms-pRferfe were used to construct a fertile pool, and the corresponding sterile plants with genotypes Ms-pMs-prferfe or Ms-pms-prferfe were used to con- struct a sterile pool. The fertility restoring gene Rfe was mapped to one side of the microsatellite markers RM311 and RM3152 on rice chromosome 10, with genetic distances of 7.9 cM and 3.6 cM, respectively. The microsatellite markers around the location of the Ms-p gene were used to finely map the Ms-p gene. The findings of this study indicated that the microsatellite markers RM171 and RM6745 flanked the Ms-p gene, and the distances were 0.3 cM and 3.0 cM, respectively. On the basis of the sequence of rice chromosome 10, the physical distance between the two markers is approximately 730 kb. These findings facilitates molecular marker-assisted selection （MAS） of genes Ms-p and Rfe in rice breeding programs, and cloning them in the future.

Inheritance of Fertility Restoration for Cytoplasmic Male Sterility in a New Gossypium barbadense Restorer

In order to clarify inheritance mechanism of fertility restoration for cytoplasmic male sterility （CMS） in a new Gossypium barbadense restorer line Hai R which was found in the fertility test crossing of G. hirsutum CMS lines with G. barbadense germplasms. 23 fertility segregation populations of F2 and backcross were used to analyze the inheritance of fertility restoring gene（s） of Hai R. The result showed that Hai R had one major dominant gene （RfB） to control the CMS fertility restoration and this fertility restoration gene functioned at the sporophytic level. The sterile cytoplasm background might not only influence the transmission rate of male gamete but also that of female gamete when the restorer gene was recessive. It could be deduced that this fertility restoration gene might come from G. harknessii cotton, Hai R is of value in the application of cotton interspecific hybrid breeding.