Genetic Analysis And Gene Mapping Of A Spontaneous Genic Male Sterility Mutant In Rice (Oryza Sativa L.)

Crop fertility character was one of the most important agronomic traits of crop,and was key factor of the utility of heterosis in hybrid crop.The male sterility of rice was a common phenomenon occasionally occurring in plant,and the study of male sterility of rice had important utilizing value of rice breeding.In this research,the spontaneous rice mutant with male sterility,SC-ms-2,was obtained from the F4 progenies of the cross D 297B X Changfeng B.The cross was between SC-ms-2 and Hua B along with some other rice materials.The fertility character,morphological cytology and genetic analysis were studied by us.At the same time,with using bulked segregation analysis,the recessive genic male sterility gene was fine mapping by SSR molecular maker.The main results are summarized as bellows:1.The anther of SC-ms-2 was white,transparent,gracile and produced male sterility pollen.It belonged to pollen type.The sterility character was stable,not affected by temperature and light change,but the pistil of glume and other flower structure were normal.Furthermore,all of the F₁ plants from crosses between this mutant and wild type were male fertile.The fertility and male sterility were segregated in all the F₂ populations from the three crosses and the segregation ratios fit well to 3:1.These results indicated that male sterility phenotype of this mutant SC-ms-2 was controlled by a single recessive genic gene,which didn't affect by cytoplasm.2.By observation of paraffin section,SC-ms-2 and wild type had no differentiation in the microspore mother cell stage,prophase stage of meiosis and tetrad stage before microspore morphogenesis.After the pollens developed in the microspore morphogenesis, the tapetum of wild type concentrated and disassembled normally,but the microspore of male sterility mutant were oafish,the tapetum cells was incrassated,at last microspore couldn't be develop normal pollens.3.Comparing with heterozygote of near-isogenetic lines,the result of genetic effect analysis showed that the growth duration of SC-ms-2 had 84 days,0.67 days more than heterozygote;the plant height had 84 cM,13.39cM lower than heterozygote;the valid spikes were 10.3,1.1 more than heterozygote;the panicle length was 24.6cM,3.8cM longer than heterozygote;the spikelets per panicle had 176 grains,38.4 grains more than heterozygote;at the same time,the panicle enclosure rate of SC-ms-2 was 7.34%,and the panicle enclosure length rate was 26.65%.4.According to genetic analysis,by using bulked segregation analysis on an F₂ population developed from the cross of SC-ms-2 and Hua B,this gene was mapped close to two simple sequence repeat(SSR) makers,RM24431 and RM3600,on chromosome 9. Further,fine mapping was carried out by using the F₂ population developed from the cross between MS-sc-2 and Nipponbare,and this gene was located between SSR molecular maker RM24451 and RM7048,with genetic distance of 0.3 cM and 0.6 cM,respectively, and physical distance approximately 172 kb.Bioinformatics analysis showed that LOC_Os09g27620 maybe the target gene.Our results showed that this gene was distinguished from all other genes with male sterility in rice reported,and it was designated ms92(t),temporally.