Genetic Analysis And Mapping Of Rice(Oryza Sativa .L) Male-sterile (Osms2 And Osms3 ) Mutants

To research the mechanism of pollen grains development ,two rice male-sterile mutants Osms2 and Osms3 of japonica cultivar 9522 background, were obtained from the M2 mutant pool mutagenized by ⁶⁰Coγ-Ray. Genetic analysis indicated that the male-sterile phenotype was controlled by a single recessive gene.Results of tissue section showed that before tetrad stage Osms2 tapetum and microspores were similar with those of wild type, Then microspores degenerated. No matured pollens were observed in Osms2 anther locus. The acetolysis experiment showed that the exine of pollen grains was abnormal ,which resulting in the mutant phenotypes. To map OsMS2 locus, an F₂ population was constructed from the cross between the Osms2 (japonica) and guangluai(indica). Firstly, the OsMS2 locus was roughly mapped between two InDel markers, OS302 and SJ302 on chromosome 3. And then six polymorphic markers were developed for further fine-mapping. At last the OsMS2 locus was mapped between the two InDel markers, CL6-4 and CL7-4 with genetic distance of 0.1 cM and 0.04CM, respectively. The region was delimited to about 100 kb. In this region, there are 13 predicted genes referring to TIGR database (http://www.tigr.org), in which a similar to MS2 gene was homologic to Arabidopsis male-sterile gene MS2. The result of sequence analysis showed a deletion of one nucleotide in the eighth exon, which resulted in shifed encode frame. All these results indicated the OsMS2 gene was just the candidate gene whose loss of fuction leading to the mutant phenotypes.Observation of tissue section showed that Osms3 microspore mother cells could undergo normal meiosis, and dyads and tetrads of microspores were generated.