Fine Mapping of Inter-Subspecies Hybrid Pollen Sterility Gene in Rice (Oryza Sativa L.) and Phylogenetic Analysis
|School||Nanjing Agricultural College|
|Keywords||Oryza Sativa indica-japonica hybrid hybrid sterility fine mapping phylogenetic analysis|
Cultivated rice has a strong heterosis of inter-subspecific hybrids. Using these advantage may increase the rice yield. However, the F1 semi-sterility has been a major barrier for the utilization of the strong heterosis between indica and japonica. The discovery of wide compatibility genes (WCGs) has brought breeders hope for breaking the fertility barrier. This S5n has been incorporated into indica or japonica variety to overcome sterility problem in wide crosses and hybrid rice breeding, so far, the S5n allele has been effective to produce fertile hybrids in a large number of crosses. The genetic study of hybrid sterility led to the finding of a neutral allele or wide compatibility allele.In this research, one of parents Ketan Nangka is Java carrying S5n and S15n, N22 belongs to indica, but it is compatible, too. However, the typical partial pollen sterility shown in the F1 hybrids between Ketan Nangka and N22, the hybrid semi-sterility locus was found by constructing chromosome 1 molecular linkage maps and the result showed it was qPS-1 locus. Fine mapping of qPS-1 was done. The other people in our laboratory found this locus using the backcross population 02428/Yunnan weedy rice//02428. The result of qPS-1 locus’fine mapping in his study is identical to my research. In our study, with phylogenetic analysis of two SNPs in SaM、SaF, approach to study the differentiation of indica and japoncia. The main findings are as followings:The hybrid of Ketan Nangka/N22 reveals partial pollen sterility.1% I2-KI staining pollen was abnormal, belonging to typical sterility and pollen fertility was 52.4±2.4%. Regression analysis showed that spikelet fertility and pollen fertility were positively correlated. So pollen abortion was the main reason for semi-sterility. Genetic mapping in a BC1F1 population(Ketan Nangka/N22//Ketan Nangka) showed that a major QTL for hybrid pollen sterility (qPS-1) was present on chromosome 1. qPS-1 was fine-mapped to a 110kb region known to contain the hybrid pollen sterility locus Sa. Sequencing Sa locus in Ketan Nangka and N22, suggested that qPS-1 is allelic with Sa.Then we selected 114 rice varieties to elucidate the evolution of SaM and SaF genes. By studying the two functional SNPs in Sa site, we found that this gene differentiated in indica, wide rice, and weedy rice but not in japonica. We also selected 96 rice varieties, including 4 test varieties, weedy rice, wide rice and some typical local japonica varieties, for cluster analysis. The result showed that among indica there is a significant differentiation in SaM and SaF genes. This result provides reference for resolving reproductive isolation and it is the key to make full use of heterosis of rice.