Development of novel wheat-rye 6RS small fragment translocation lines with powdery mildew resistance and physical mapping of the resistance gene PmW6RS.

Novel wheat-rye 6RS small fragment translocation lines with powdery mildew resistance were developed, and the resistance gene PmW6RS was physically mapped onto 6RS-0.58-0.66-bin corresponding to 18.38 Mb in Weining rye. Rye (Secale cereale L., RR) contains valuable genes for wheat improvement. However, most of the rye resistance genes have not been successfully used in wheat cultivars. Identification of new rye resistance genes and transfer of these genes to wheat by developing small fragment translocation lines will make these genes more usable for wheat breeding. In this study, a broad-spectrum powdery mildew resistance gene PmW6RS was localized on rye chromosome arm 6RS using a new set of wheat-rye disomic and telosomic addition lines. To further study and use PmW6RS, 164 wheat-rye 6RS translocation lines were developed by 60 Coγ-ray irradiation. Seedling and adult stage powdery mildew resistance analysis showed that 106 of the translocation lines were resistant. A physical map of 6RS was constructed using the 6RS translocation and deletion lines, and PmW6RS was localized in the 6RS-0.58-0.66-bin, flanked by markers X6RS-3 and X6RS-10 corresponding to the physical interval of 50.23-68.61 Mb in Weining rye genome. A total of 23 resistance-related genes were annotated. Nine markers co-segregate with the 6RS-0.58-0.66-bin, which can be used to rapidly trace the 6RS fragment carrying PmW6RS. Small fragment translocation lines with powdery mildew resistance were backcrossed with wheat cultivars, and 39 agronomically acceptable homozygous 6RS small fragment translocation lines were obtained. In conclusion, this study not only provides novel gene source and germplasms for wheat resistance breeding, but also laid a solid foundation for cloning of PmW6RS.