Molecular cytogenetic identification of wheat-Aegilops geniculata derivative line with resistance to powdery mildew encoded on chromosome 6Ug.

Aegilops geniculata Roth is a valuable donor for improving common wheat (Triticum aestivum) because of their close relationship. In this study, W181009 was identified as a BC₁F₁₂ progeny resulting from the cross between "Chinese Spring" (CS) and Ae. geniculata SY159. Cytological examination, fluorescence in situ hybridization, and functional markers analysis confirmed that W181009 carried alien chromosomes 2M^g and 6U^g from Ae. geniculata SY159. Utilizing the specific locus amplified fragment sequencing (SLAF-seq) technique, we successfully developed specific markers for W181009 with an effective rate of 54.23%. Subsequently, the deletion of chromosome 6B in W181009 was confirmed using deletion nullisomic-tetrasomic lines. Notably, W181009 showed immune resistance to powdery mildew at all growth stage. To further study the source of the powdery mildew (Blumeria graminis) resistance gene in W181009, a genetic population was created using W181009 and Shaanyou225 (SY225) for analysis. Both F₁ and BC₁F₂ plants carried chromosome 6U^g and they exhibited strong resistance against powdery mildew, indicating that the resistance in W181009 originated from chromosome 6U^g. Furthermore, the presence of only chromosome 6U^g can be easily identified by using two specific SLAF-seq markers. The study results provide the basis for further genetic research and breeding to improve powdery mildew resistance using W181009.