Mapping Of Powdery Mildew Resistant Gene And Inheritance Of HMW-GS In Wheat-Thinopyrum Introgressions

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a globally important disease of wheat, which seriously constraints on wheat production. The breeding of resistant varieties is the most feasible means of controlling the disease. At present, the international experts have identified more than 67 powdery mildew resistance genes on different chromosomes or arms. Even though some genes have been applied successfully to wheat breeding programs, several resistant cultivars have become ineffective with the large-scale cultivation of resistant varieties. Therefore, it is necessary for the ongoing identification and utilization of new resistance genes.Thinopyrum intermedium (2n=42, JJJsJsStSt) carrys many excellent resistance genes aginst wheat disease, it is a valuable source of wheat resistance breeding. To utilize these excellent genes, some attempts have been made to transfer resistance genes into wheat from Th. intermedium, and many multi-resistance lines including CH7124 and CH03W006 have been developed by crossing susceptible wheat cultivars with resistant partial amphiploids as donor parents. By using genetic analysis, GISH and molecular markers, we determined the inheritance, chromosome location and linkage to molecular marhers of wheat introgression line CH7124. According to collinearity among the cereal crops, by using comparative genomics to develop new molecular markers, we built satured linkage map of the loci linked to Pm43. In this study, we also analyzed the compositions of HMW-GS in one hundred forty Th. intermedium-derived lines. The main results are as follows:(1) Wheat introgression line CH7124 derived from wheat-Th. intermedium line TAI8335 exhibits immunity to Bgt pathotypes E09, E20, E21, E23, E26, Bgl, and Bg2 at the seedling stage. The Bgt resistance in CH7124 is similar to that in TAI8335 and its wild parent Th. intermedium. However, no Th. intermedium chromatin has been detected according to genome in situ hybridization (GISH) assay. In this study, we determined the single dominant Bgt resistance gene in CH7124, tentatively designated PmCH7124, using populations derived from SY95-71/CH7124 (F6) and CH7124/Mianyangll (F1 and F2). Five SSR markers (Xgwm47, Xgwm120, Xwmc332, Xgwm501, and Xbarc 101) were identified to be codominant with PmCH7124 according to bulked segregant analysis, and the closely flanking markers were Xgwm501 and Xbacr 101 with genetic distances of 1.7 cM and 4.5 cM, respectively. The target resistance gene was chromosomally located on 2BL with Chinese Spring nulli-tetrasomic and ditelosomic lines. We primarily consider that PmCH7124 is a new Bgt resistance gene because its resistance spectrum, origin, chromosomal location, and linked markers are different from those of the known Bgt resistance genes, such as Pm6, Pm33, Pm51, Pm52, PmJM22, MlZecl, and MlAB10.(2) By using comparative genomics to develop three EST-PCR markers, we found the collinearity among the second homologous chromosome groups in the wheat, the fourth homologous chromosome groups in the rice, and the fifth homologous chromosome groups in the brachypodium distachyon. Building of the satured linkage map of the loci Pm43 will be beneficial to map-based gene cloning and gene function characterization.(3) By using SDS-PAGE analysis, genetic diversity of 140 plants derived from the F2 segregating populations that wheat-alien introgression lines CH03W006 crossed with common wheat Taichang 29 were analyzed in this study. The results showed that there was no linkage relationship among different subunits in the loci of Glu-1. The F2 segregating population showed abundant of genetic diversity,3 HMW-GS types were found in Glu-A1,10 HMW-GS types in Glu-B1 and 4 HMW-GS types in Glu-D1. And 19 composition types appeared. High quality subunits 2*,7+8/13+16/17+18 and 5+10/5+12 were detected respectively in three different Glu-1 locis. Cluster analysis indicated the F2 segregating population is closely related to the male parent CH03W006, and these wheat-alien introgression lines derived from distant hybridization express plentiful HMW-GS variations, and genetic diversity among these wheat-alien introgression lines with plentiful HMW-GS variations exsits patroclinal inheritance.