| A semi-sterility mutant, whose seeds-set was about 40 percent, was found in the field of Japonica rice variety Nipponbare in Japan in 1991. Segregation of fertility was found in the progenies of the semi-sterile plant, but the segregation ratio between fertile plants and semi-sterile plants was unexpected. Through self-crossing and selecting the semi-sterile plants till 1996, 13 lines whose semi-sterility inherited to their progenies stably were selected from 20 semi-sterile lines. In order to explore the semi-sterility, we selected a semi-sterility mutant line W207-2 and constructed F2 populations, BC1F1 populations and F2:3 family, which were derived from the crosses between W207-2 and its wild variety Nipponbare, wide compatibility rice variety CPSLO17, respectively. Furthermore a rice framework linkage map was constructed using the F2 population derived from W207-2/CPSLO17. Based on the map, the semi-sterility QTLs were detected simultaneously in. F2 population and F2:3 family. The results as follows:1 Genetic analysis for semi-sterility in riceWe investigated the fertility of W207-2 and its FI hybrids of the reciprocal crosses, F2 populations, BCiFi populations and F23 family, which were derived from the crosses with Nipponbare and CPSLO17, respectively. The results indicated that the semi-sterility was controlled by nucleus genes with little cytoplasm effect.2 Construction of a rice framework linkage mapA molecular map containing 118 SSR markers was constructed using the F2 population containing 157 individuals derived from W207-2/CPSLO17. The map covered 1898.8cM on all 12 chromosomes with an average interval size of 16.09cM. 112 of 118 determined marker orders agreed with those of the published rice linkage maps.3 Gene mapping for semi-sterility in riceBased on the linkage map constructed, QTLs controlling semi-sterility were detected using software MAPMAKER/QTL 1.1. In F2 population, one pollen semi-sterility QTL detected was bordered by markers RM152 and RM6863 on chromosome 8. Two spikelet semi-sterility QTLs detected were bordered by markers RM152 and RM6863 onchromosome 8, RM228 and RM333 on chromosome 10, respectively. In F2:3 family, two pollen semi-sterility QTLs detected were located at the region of markers RM118 and RM172 on chromosome 7, RM152 and RM6863 on chromosome 8, respectively. Three spikelet semi-sterility QTLs detected were located at the region of markers RM168 and RM143 on chromosome 3, RM234 and RM118 on chromosome 7, RM152 and RM6863 on chromosome 8, respectively.The semi-sterility QTLs detected in F2 population and F2:3 family were compared. The locations of the LOD peak for pollen semi-sterility QTL and spikelet semi-sterility QTL, which were detected on chromosome 8 in F2 population, were at the same region. The distances between the QTLs and marker RM152 were both 7.0cM. We considered that they were the same QTL, which influenced the spikelet semi-sterility by controlling the pollen semi-sterility. The spikelet semi-sterility QTL detected on chromosome 10 was not related with the pollen fertility. The values of LOD and phenotypic variation of the two QTLs were very high, which suggested that they were two major effect QTLs. The values of LOD and phenotypic variation of the QTLs detected on chromosome 3 and 7 in p2:3 family were very low. So we concluded that the semi-sterility in this study was controlled by two major effect QTLs on cliromosome 8 and 10, respectively. Except these two QTLs, some minor effect QTLs influenced the semi-sterility.4 Detection of segregation distortions in the rice linkage mapThe frequencies of genotypes for 118 SSR markers with 157 individuals were plotted along the rice linkage map constructed previously to detect segregation distortion. We detected 12 segregation distortions on chromosome 3, 4, 5, 6, 7, 8, 9 and 12. In this study, segregation distortion was not detected at the regions of the semi-sterility QTLs. It suggested that the semi-sterility QTLs were not affected by the segregation distortion, and the results o...
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