Gene Mapping And Application Of Small Grain Mutant In Rice

Small grain mutant ZH-sg, irradiated by γ-ray from japonica rice Zhonghua 11 cultivated by Institute of Crop Science of Chinese Academy of Agricultural Sciences, was studied on phenotype identification and genetic analysis. The results indicated that the mutant merely act on grain shape and has none business with other agronomic traits. Another semi dwarf mutant Aizhonghua, also induced from Zhonghua 11, was crossed with ZH-sg to construct F2 populations. The plant height and grain presented typical separation ratio of 9(tall plant with normal grain) : 3(tall plant with small grain) : 3(semi dwarf with normal grain) : 1(semi dwarf with small grain), that suggests that two mutants controlled by independent single recessive nuclear genes respectively. Neixiang 2, a large grain indica variety cultivated by Institute of Neijiang Agriculture Science Research in Sichuan, was crossed with mutant ZH-sg. From F2 populations a slight small grain was selected, the new combination by self generation inbred was obtained, the slight small grain pure line named Xixiang. Xixiang was crossed with ZH-sg to construct F1 and F2 populations, while F1 showed normal grain and F2 presented typical separation ratio of 3(normal grain) : 1(small grain). Including other genetic analysis of crosses, the results indicated that the small grain gene is also a single recessive nuclear gene. Allelism test proofed that small grain are allelic gene between ZH-sg and Xixiang. Using F2 population of Neixiang 2 crossed with Xixiang, the small grain mutant gene was mapping and locating on 950 kb intervals between 7-2-1 and 3A-1 of Indel markers.Xinei s(temperature sensitive genetic male sterile line with small grain) and Zhongqiao A(cytoplasmic male sterile line with small grain) as female parents, by promoting with CO2 to blossom out, crossed respectively with nine different large grain varieties as male parents. Statistic data of hybrid seeds indicated that there is no obvious Xenia Effect in the grain shape. The seeds mixed between small grain hybrid seeds and large grain male parents went through the sieve, the purities of hybrid seeds were all over 97.5%, which can meet the needs of hybrid seed production. The agronomic traits of F1 and their parents’ varieties represented that the number of tiller per plant, the number of filled grains per plant, and the weight per plant showed strong hybrids vigor and were all significantly higher than that of parents. The hybrid seed production by small grain as female crossed with large grain as male can be feasible and useful, when mechanization in field and by filter on sieve.The examination including small grain hybrids, normal grain hybrids, small and large grain conventional varieties, as well as excellent hybrid rice Tianyouhuazhan as check, simulated late cropping of double season by seedling on seedbed and rice transplanting by machine in Yangtze Downriver Rice Production Area. The results of seedling experiment indicated that small grain hybrids and small grain conventional varieties can extend seedling stage without any agricultural technique for about 3 days under natural conditions. While seedling qualities had no significant depressed, the yield traits of small grain hybrids were F1s’ vigor and significantly better than their parents, although have been some way to catch up with large grain hybrids and excellent check hybrid. The better combinations with small grain as female for hybrid seeds production, depends on female and male parents’ breeding continuously, and more mating.