Microsatellite mapping of powdery mildew resistance allele Pm5d from common wheat line IGV1-455

The powdery mildew resistance allele Pm5d in the backcross-derived wheat lines IGV1-455 (CI10904/7*Prins) and IGV1-556 (CI10904/7*Starke) shows a wide spectrum of resistance and virulent pathotypes have not yet been detected in Germany. Although this allele may be distinguished from the other documented Pm5 alleles by employing a differential set of Blumeria graminis tritici isolates, the use of linked molecular markers could enhance selection, especially for gene pyramiding. Pm5d was genetically mapped relative to six microsatellite markers in the distal part of chromosome 7BL using 82 F ₃ families of the cross Chinese Spring × IGV1-455. Microsatellite-based deletion line mapping placed Pm5d in the terminal 14% of chromosome 7BL. The closely linked microsatellite markers Xgwm577 and Xwmc581 showed useful variation for distinguishing the different Pm5 alleles except the ones originating from Chinese wheat germplasm. Their use, however, would be limited to particular crosses because they are not functional markers. The occurrence of resistance genes closely linked to the Pm5 locus is discussed.