水稻小穗退化突变体spd-hp73的遗传分析及基因定位

Genetic analysis and gene mapping of a rice spikelet degradation mutant(spd-hp73)

为了深入研究水稻幼穗发育及调控机制,经60 Co-γ射线诱变处理,获得一小穗退化突变体spd-hp73。经考察,与野生型hp73(CK)相比,该突变体生长势较弱,生育期提早,株高偏矮,分蘖数较少,包颈明显;同时,还显示出异常的花序结构,主要包括小穗严重退化,每穗粒数显著减少,着粒密度很低和结实率下降等。遗传分析表明,spd-hp73小穗退化突变性状受1对隐性基因控制,暂命名为spd-hp73。利用519个SSR分子标记,以spd-hp73×浙7954的448个单株F2作为定位群体,将小穗退化突变基因spd-hp73初步定位在第4染色体长臂RM471和RM273之间,与RM471和RM273的遗传距离分别为12.2cM和9.4cM。该结果为突变基因的精细定位和克隆奠定了良好基础。

Summary The structure of rice spikelet, an important determinant of yield and rice quality, is a hot topic in rice research areas. The structure of spikelet is somewhat complex, and its development is influenced by multiple factors, including genetic factors and environmental factors. Two major technical routes in studying molecular mechanism of the structure of spikelet are used： one is homologous sequencing of the dicotyledonous plant to screen the rice eDNA library and obtain the related genes, and the other is creating some spikelet character mutants with locating and cloning the mutant genes to grasp the genes function included. In order to further study rice spikelet development and its mechanism of regulation, we used a spikelet degradation mutant （spd-hp73）, which was obtained from the offspring of hp73 mutated by s0 Co-）＇ radiation. In this study, the characteristic and genetic stability of rice spikelet of spd-hp73 mutant in different environments were investigated. And three crosses were made between the spikelet degradation mutant （female parent） and the wildtypes Zhe7954,9311, Minghui63 （male parents） to investigate the inheritance pattern of the mutation. And 519 SSR molecular markers were used for mutant genetic analysis. The mapping populations were derived from a cross between spd-hp73 and Zhe7954. Compared with the wild-type （hp73）, the spd-hp73 mutant showed several abnormal agronomic characteristics, including weak growth, early flowering, low germination, scrubby plant, few tillers, thin stems, short leaves and clear closure of spikelet. Furthermore, the branches were twisted at different degrees, and the secondary branch was longer than hp73. Moreover, spd-hp73 exhibited abnormal inflorescence architecture, including the abundant degradation of spikelet, significant reduction of the grains per spikelet, low grain density and decreased seed setting rate. The traits of mutant were expressed stably in different growth environments. Spikelet degradation mutant resulted in a remarkable negative effect on rice normal growth and reproductive growth. Genetic analysis indicated that the special phenotype was controlled by a single recessive gene, named spd-hp73. The mutation site was preliminarily mapped to the long arm of chromosome 4： between SSR markers RM471 and RM273 with 12.2 cM and 9.4 cM intervals, respectively. These results of preliminary genetic analysis lay a foundation for fine mapping and cloning of spikelet degradation gene. Probably, spd-hp73 plays an important role in further understanding the regulation mechanism of entire spikelet development.