Fine Mapping of the Blast Resistance Gene P/75, Linked to Pii, on Rice Chromosome 9

稻瘟病抗病基因Pi15的精细定位(英文)

The gene Pi15 for resistance of rice to Magnaporthe grisea was previously identified as being linked to the gene Pii. However, there is a debate on the chromosomal position of the Pii gene, because it was originally mapped on chromosome 6, but recent work showed it might be located on chromosome 9. To determine the chromosomal location of the Pi15 gene, a linkage analysis using molecular markers was performed in a F2 mapping population consisting of 15 resistant and 141 susceptible plants through bulked-segregant analysis (BSA) in combination with recessive-class analysis (RCA). Out of 20 microsatellite markers mapped on chromosomes 6 and 9 tested, only one marker, RM316 on chromosome 9, was found to have a linkage with the Pi15 gene with a recombination frequency of (19.1 ±3.7)%. To confirm this finding, four sequence-tagged site (STS) markers mapped on chromosome 9 were tested. The results suggested that marker G103 was linked to the Pi15 gene with a recombination frequency of (5.7±2.1)%. To find marker(s) more closely linked to the Pi15 gene, random amplified polymorphic DNA (RAPD) analysis was performed. Out of 1 000 primers tested, three RAPD markers, BAPi15486, BAPi15782 and BAPil5844 were found to tightly flank the Pi15 gene with recombination frequencies of 0.35%, 0.35% and 1.1%, respectively. These three RAPD markers should be viewed as the starting points for marker-aided gene pyramiding and cloning. A new gene cluster of rice blast resistance on chromosome 9 was also discussed.

稻瘟病抗病基因Pi15曾被作者鉴定为与已知抗病基因Pii具有连锁关系,但是,Pii基因究竟位于染色体6还是9上存在争议。为了确定Pi15基因的染色体位置,利用分子标记在由15个抗病个体和141个感病个体组成的F_2群体中,通过混合群体分离法(BSA)与隐性群体分析法(RCA)相结合的手段,对目标基因进行了连锁分析。首先,从染色体6和9分别选择10个微卫星标记进行了分析,结果表明,只有位于染色体9的RM316与目标基因连锁,重组率为(19.1±3.7)％。为了进一步确定这种连锁关系,从染色体9选择了4个序列标定位点(STS)标记进行分析,结果表明,只有G103与目标基因连锁,重组率为(5.7±2.1)％。为了获得与目标基因更加紧密连锁的分子标记,对目标基囚进行了RAPD分析。在筛选、分析了1000个随机引物之后,从中获得了3个目标基因紧密连锁的分子标记BAPi15_(486)、BAPi15_(782)、BAPi15_(844)。它们与目标基因的重组率分别为0.35％、0.35％和1.1％。这些紧密连锁的分子标记可作为分子标记辅助基因聚合和克隆的出发点。