Genetic analysis of resistance to powdery mildew on 7Mg chromosome of wheat-Aegilops geniculata, development and utilization of specific molecular markers

Background: Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is prevalent in the main wheat-producing regions of China, resulting in severe yield losses in recent years. Mining and utilization of resistant genes from wild relatives of wheat is the most environmentally sound measure to control disease. Aegilops geniculata Roth (2n = 2x = 28, (UUMMg)-U-g-M-g-M-g) is an essential and valuable disease-resistance gene donor for wheat improvement as a close relative species. Results: In this study, to validate powdery mildew resistance locus on chromosome 7M(g), two genetic populations were constructed and through crossing wheat - Ae. geniculata 7M(g) disomic addition line NA0973-5-4-1-2-9-1 and 7M(g) (7 A) alien disomic substitution line W16998 with susceptible Yuanfeng175 (YF175, authorized varieties from Shaanxi province in 2005), respectively. Cytological examination, in situ hybridization (ISH), and functional molecular markers analysis revealed that the plants carrying chromosome 7M(g) showed high resistance to powdery mildew in both F-1 and F-2 generation at the seedling stage. Besides, 84 specific markers were developed to identify the plants carrying chromosome 7M(g) resistance based on the specific-locus amplified fragment sequencing (SLAF-seq) technique. Among them, four markers were selected randomly to check the reliability in F-2 segregating populations derived from YF175/NA0973-5-4-1-2-9-1 and YF175/W16998. In summary, the above analysis confirmed that a dominant high powdery mildew resistance gene was located on chromosome 7M(g) of Ae. geniculata. Conclusion: The results provide a basis for mapping the powdery mildew resistance gene mapping on chromosome 7M(g) and specific markers for their utilization in the future.