Genetic And Applied Studies On SiChuan's Rcessive Male Sterility In Rice (Oryza Sativa L.)

Male sterility is a common phenomenon occasionally occurring in plant. The success of three-line hybrid rice application gave much drive to the pace of nucleolus-cytoplasm complementary sterility (CMS) research. The simplicity and the temperature-light impregnability of the recessive nuclear male sterility (RNMS) made its genetic mechanism a fine model for male sterility and heterosis application research. Using a mutated RNMS rice line (H₂S) from Sichuan Province, A RNMS gene was identified and fine mapped, and its genetic effect was studied. The results of the Mendelian genetics, genetic effect, morphological cytology, chromosome localization, and the breeding application study were as follows:1. The waterlogging like white anther of H₂S line was slender and small and produced no pollen, but the pistil in the glume was normal. The male sterility of the line was stable, not affected by temperature and light change.2. RNMS was a recessive trait controlled by only one gene in nucleolus, and its sterility was restorable in wide genetic spectrum (all indica rice lines can be its restorers). Under the genetic background of Zhenshan97A(CMS-WA), D702A(CMS-D), G46A(CMS-G), K18A(CMS-K), XieqingzaoA(CMS-DA) and YuetaiA(CMS-HL), RNMS showed no nucleolus-cytoplasm gene interaction, suggesting it was a independent gene system from CMS. It was deduced that the genotype of H₂S was N(rrmsms).3. Homozygous, heterozygous and wild-type near-isogenetic lines of RNMS gene were constructed by backcrossing, and the agronomic trait investigation found that RNMS gene had positive effects on seeding-heading days and effective tillers, negative effects on plant height and grain number per panicle, no significant effect on panicle length.4. Five isonuclear alloplasmic lines with 5 different CMS cytoplasms sharing the same H₂S nucleolus were constructed. Compared with the five CMS lines, RNMS line was a little lower, its panicle was less enclosed and had smaller number of grains. The RNMS gene made no significant difference in seeding-heading days, effective tillers and panicle length. Combining ability analysis suggested that the General Combining Ability (GCA) of the RNMS line was significantly higher than other CMS lines in grain yield, plant height and seed setting rate, lower GCA in grain number per panicle. No significant GCA difference was found in other agronomic traits. Significant GCA difference was found among the 5 types of CMS lines in grain weight, grain number per panicle and grain yield.5. Through electron microscope scanning of the early floral organs, morphogenesis of the spikelet primordium, stamen primordium and pistilliod primordium was found normal. Paraffin slides observation found that the microspore of the RNMS line failed to vacuolate after its morphogenesis, disassembled and disappeared at last. After microspore morphogenesis, the breaking down of tapetum cells was delayed until microspore breading down. It was speculated that the sterility of the RNMS line was related to the delay of tapetum cells' breaking down.6. Through bulked extremes and recessive class analysis with SSR markers and INDEL markers, the RNMS gene in H₂S line was fine mapped between W19 and W11, 0.5cM and 0.2cM away from the target respectively. 11 genes was found in the region of 73Kb between the two markers, bioinformatics analysis showed that LOC_Os06g42310 maybe the target gene. Literature search suggested that the gene was a new one, so we named it ms-nop(t) temporally.7. Recurrent selection and breeding research of the RNMS was conducted, the results showed that higher grain yield GCA lines can be produced by transferring the RNMS gene. Using RNMS gene as a outcrossing means, recurrent selection population breeding programs were launched, and a number of elite rice lines had produced, such as D35A and Shuhui498 and D83A. The hybrids combinations with these parental lines showed outstanding performance in the authority of the Province plot test, related hybrids varieties were examined and approved by the Province authority.