Fine Mapping and Toward Physical Mapping of Powdery Mildew Resistance Gene MlIW172 Originating from Wild Emmer (Triticum dicoccoides)

Powdery mildew, caused by Blumeria graminis f.sp. tritici, is one of the most important wheat diseases in the world. A single dominant powdery mildew resistance gene MlIW172 was identified in wild emmer accession IW172 and located on distal of chromosome 7AL (bin7AL-16-0.86-0.90) via molecular marker analysis. MlIW172 was closely linked with RFLP probe Xpsr680-derived STS marker Xmag2185 and EST markers BE405531 and BE637476, suggested that MlIW172 might be allelic to Pm1 locus or a new locus closely linked to Pm1. Comparative genetics analysis using MlIW172 flanked ESTs and RFLP probe sequences against rice, Brachypodium and sorghum genome sequences revealed high co-linearity among the MlIW172 orthologous genomic regions of rice chromosome 6, Brachypodium Bd1 and sorghum chromosome 10. By screening BAC libraries of wild emmer wheat IW2, durum wheat Langdong and Chinese Spring 7AL, and using genome scaffold information of T. urartu, a fine genetic linkage map and physical map of MlIW172 are developing toward a map-based cloning of the powdery mildew resistance gene.