Evaluation Of Wild Wheat Accessions For Powdery Mildew Resistance And Molecular Mapping Of The Pmx Gene In One Emmer Accession

Powdery mildew, caused by Blumeria graminis (DC.) E.O. Speerf. sp. Tritici, is one of the most important diseases of common wheat world-wide. Breeding for resistant cultivars has been proven to be the most effective way to control this disease, for which screening for and utilization of diverse resistance genes are the prerequsite. Development of molecular markers and construction of molecular marker maps of wheat facilitate the studies of the resistance genes. The wheat relative species are rich in resistance genes for powdery mildew disease. In the study, a batch of wild wheat accessions including einkorn and emmer were evaluated for their resistance to this disease, and the resistance gene Pmx in the wild emmer accession ' 21446' was mapped by using SSR markers.Thirty-seven accessions and twenty-four accessions of einkorn and emmer wheat were evaluated for resistance to powdery mildew at the seedling stage. The result indicated that fifteen, four and five einkorn accessions were immune, nearly-immune and highly resistant, respectively. Of the emmer accessions, four, two and four were immune, nearly-immune and highly resistant, respectively. The latent period of powdery mildew in nearly-immune and highly resistant accessions was significantly longer than that in the susceptible accessions.The emmer accession ' 21446' was immune to powdery mildew at the whole growth stage and its resistance was determined by a dominant gene temporarily designated as Pmx. A F3 line segregating for Pmx, derived from the cross between the susceptible accession ' 21437' and the resistant accession ' 21446' , was used to identify molecular markers linked to Pmx. It was found that Pmx was flanked by Xgwm344 and Xgwm666, with a genetic distances of 8.7cM and 21.7cM, respectively. The close linkage of Xgwm344 to Pmx was confirmed by using four F4 lines derived from Pmx-carrying plants in the F3 line.Xgwm344 was mapped to chromosome 7BL by using the six C.S. ditelosomics of group7, which indicated that Pmx was located on the long arm of chromosome 7B. Pmx was not identical to the known powdery mildew resistance genes located on 7BL because of its dominance character.