| Wheat stripe rust, caused by Puccinia striiformis West. f. sp. tritici, is one of the most important wheat disease in the world, which can be spread by air and result in great loss. China is a big wheat-growing country, and the biggest epidemic region of wheat stripe rust. Wheat production in China is threatened by stripe rust every year. At present, the simplicity of stripe rust resistance background in commercial wheat cultivars have not changed at all though a lot of cultivars are used in wheat production.The wheat variety C591, introduced from India years ago, has excellent resistance to stripe rust in China. C591 is a hexaploid wheat, has some excellent agronomic traits and can easily used in wheat breeding through cross. Whereas the shortage of new stripe rust resistance resources for wheat breeding and some effective stripe rust resistance resources, for example C591, have not been utilized reasonably, to carry out studies on genetic analysis of resistance, chromosomal localization and development of molecular markers for the stripe rust resistance genes in the wheat variety C591 has important significance.In this study, a set of different progenies derived from the cross between a susceptible variety Taichung29 and the variety C591 were prepared. Genetic analysis of resistance was carried out by inoculating representative main races of Chinese wheat stripe rust in green house. Chromosomal localization of a major stripe rust resistance gene in C591 was performed by using SSR method combined with nullitetrasomic analysis. Molecular markers for the target gene were developed by using AFLP method. The main results gained are as follows:1. Based on the stripe rust resistance assessment results, wheat variety C591 showed excellent seedling resistance to the races of Puccinia striiformis West. f. sp. tritici inoculated. The results indicated that there were two dominant genes conferring the resistance to races CY19 and CY26, one dominant gene and two recessive genes conferring the resistance to CY29, and one dominant gene conferring the resistance to CY32.2. Through SSR analysis with resistance pool and susceptible pool, seven SSR markers on the long arm of chromosome 7B were found linked to YrC591. The SSR markers were Xwmcl66, Xwmc273, Xwmc311, Xbarc32, Xcfa2040, Xgwm577 and Xgwm984, and their genetic distances from Y(C591 were 16.6cM, 15.8cM, 37.4cM, 15.8cM, 16.6cM, 17.2cM and 16.6cM respectively.3. Nullitetrasomic analysis was conducted with SSR markers Xwmcl66, Xwmc273, Xwmc311;Xbarc32, Xcfa2040, Xgwm577 and Xgwm984. Except for Xwmcl66, the other six specific SSR markers had no amplified products in nullitetrasomic materials of 7B, but amplified well in any other 20nullitetrasomic materials. SSR primer Xwmcl66 has no special amplified band in wheat variety Taichung29, Chinese Spring and its 21 nullitetrasomic lines, but amplified in wheat variety C591. The results indicated that the specific SSR bands amplified by the six SSR primers were on wheat chromosome 7B. Combined with the SSR markers mapping results, we concluded that the major stripe rust resistance gene in C591 was on the chromosome 7BL.4. By using AFLP analyses with resistance pool and susceptible pool, seven polymorphic DNA bands were found linked to the stripe rust resistance gene YrC591, they were P38M482ig, P41M4825g, P35M48373, P34M50i9o, P37M47,i0, P39M61,24 and P41M49|50. In which, the polymorphic DNA bands P41M48258 and P35M48373 had been converted into SCAR markers successfully. Genetic linkage analysis indicated that the genetic distance between SC-P35M48, SC-P41M48 and YrC591 were 5.9cM and 8.6cM respectively.5. Assessment of stripe rust resistance of related varieties indicated that C591, which carrying YrC591 gene, showed low infection phenotype (ITO;), the wheat varieties carrying Yr2 or Yr6 genes showed high infection phenotype (IT3"-IT4). The results indicated that YrC591 should be a new stripe rust resistance gene different from Yr2 and Yr6.
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