Molecular mapping of a novel wheat powdery mildew resistance gene Ml92145E8-9 and its application in wheat breeding by marker-assisted selection

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most devastating diseases of common wheat (Triticum aestivum L.). The wheat line 92145E8-9 is immune to Bgt isolate E09. Genetic analysis reveals that the powdery mildew resistance in 92145E8-9 is controlled by a single dominant gene, temporarily designated Ml92145E8-9. Bulked-segregant analysis (BSA) with simple sequence repeat (SSR) markers indicates that Ml92145E8-9 is located on chromosome 2AL. According to the reactions of 92145E8-9, VPM1 (Pm4b carrier), and Lankao 906 (PmLK906 carrier) to 14 Bgt isolates, the resistance spectrum of 92145E8-9 differs from those of Pm4b and PmLK906, both of which were previously localized to 2AL. To test the allelism among Ml92145E8-9, Pm4b and PmLK906, two F2 populations of 92145E8-9 × VPM1 (Pm4b) and 92145E8-9 × Lankao 906 (PmLK906) were developed in this study. Screening of 784 F2 progeny of 92145E8-9 × VPM1 and 973 F2 progeny of 92145E8-9 × Lankao 906 for Bgt isolate E09 identified 37 and 19 susceptible plants, respectively. These findings indicated that Ml92145E8-9 is non-allelic to either Pm4b or PmLK906. Thus, Ml92145E8-9 is likely to be a new powdery mildew resistance gene on 2AL. New polymorphic markers were developed based on the collinearity of genomic regions of Ml92145E8-9 with the reference sequences of the International Wheat Genome Sequencing Consortium (IWGSC). Ml92145E8-9 was mapped to a 3.6 cM interval flanked by molecular markers Xsdauk13 and Xsdauk682. This study also developed five powdery mildew-resistant wheat lines (SDAU3561, SDAU3562, SDAU4173, SDAU4174, and SDAU4175) using flanking marker-aided selection. The markers closely linked to Ml92145E8-9 would be useful in marker-assisted selection for wheat powdery mildew resistance breeding.