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Powdery mildew of wheat(Triticum aestivum L.),a major fungal disease in many areas of the world,is caused by Blumeria graminis f.sp.tritici.Synthetic hexaploid wheat is an important germplasm resource for the transfer of beneficial genes from alien species to common wheat.Synthetic wheat SE5785was screened for resistance to powdery mildew during the seedling and adult stages.Genetic analyses of an F2 population and the F2:3 families,which were developed from a cross of SE5785and a susceptible common wheat,Xiaoyan 22,revealed that the powdery mildew resistance in SE5785was controlled by a single recessive gene.Molecular markers and a bulked segregant analysis were used to characterize and map the powdery mildew resistance gene.A genetic map comprised Xcfd62,Xbarc59,PmSE5785,Xgwm539,and Xwmc817,spanned 16.3 cM.Xbarc59 and Xgwm539 were flanking markers tightly linked to SE5785 at genetic distances of 3.6 and 4.0 cM,respectively.Chinese Springand its corresponding nulli-tetrasomic lines were used to confirm that PmSE5785 was located on chromosome 2D.Because no gene for powdery mildew resistance derived from the genus Triticum had been located on this chromosome arm,this was apparently a newly discovered locus and was,therefore,designated PmSE5785.From the population cross of SE5785/Xiaoyan 22,we developed two new germplasm lines,N07228-1 and N07228-2,having large seeds,powdery mildew resistance,and improved agronomic traits.These new germplasm lines could serve as sources of resistance to powdery mildew in wheat breeding.