Introgression of the Powdery Mildew Resistance Genes Pm60 and Pm60b from Triticum urartu to Common Wheat Using Durum as a 'Bridge'

Powdery mildew, caused by the fungus Blumeria graminis f. sp. tritici (Bgt), has limited wheat yields in many major wheat-production areas across the world. Introducing resistance genes from wild relatives into cultivated wheat can enrich the genetic resources for disease resistance breeding. The powdery mildew resistance gene Pm60 was first identified in diploid wild wheat Triticum urartu (T. urartu). In this study, we used durum as a 'bridge' approach to transfer Pm60 and Pm60b into hexaploid common wheat. Synthetic hexaploid wheat (SHW, AABBA(u)A(u)), developed by crossing T. urartu (A(u)A(u)) with durum (AABB), was used for crossing and backcrossing with common wheat. The Pm60 alleles were tracked by molecular markers and the resistance to powdery mildew. From BC1F1 backcross populations, eight recombinant types were identified based on five Pm60-flanking markers, which indicated different sizes of the introgressed chromosome segments from T. urartu. Moreover, we have selected two resistance-harboring introgression lines with high self-fertility, which could be easily used in wheat breeding system. Our results showed that the durum was an excellent 'bridge' for introducing the target gene from diploid T. urartu into the hexaploid cultivated wheat. Moreover, these introgression lines could be deployed in wheat resistance breeding programs, together with the assistance of the molecular markers for Pm60 alleles.