Bulked segregant RNA sequencing and linkage mapping identify a Pm4 allele conferring stable powdery mildew resistance...

Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), remains a major constraint on wheat production. Resistance genes with diagnostic markers and deployed without obvious agronomic disadvantages are essential for durable breeding. Here, we genetically and molecularly characterized powdery mildew resistance in the common wheat line YZ16 through inheritance analysis, bulked segregant RNA sequencing (BSR-Seq), linkage mapping and allele validation.

YZ16 showed high seedling resistance to Bgt isolate E09 and resistance to nine of ten additional Bgt isolates, indicating a relatively broad resistance spectrum. Under field inoculations, YZ16 also displayed stable adult-plant resistance. Genetic analysis of an F₂ population and F_2:3 families indicated a single dominant resistance gene controlling resistance, temporarily designated PmYZ16. BSR-Seq localized the resistance locus to a distal interval on chromosome 2 A (766.9-784.6 Mb), and linkage mapping revealed complete co-segregation between resistance and JS717×JS718, a functional marker of the cloned Pm4 gene. Sequencing comparison showed that the encoded protein is identical to Pm4d/Pm4e, indicating that YZ16 carries a Pm4 allele. Expression profiling further indicated dynamic regulation of two splice variants (PmYZ16_V1 and PmYZ16_V2) after Bgt inoculation. Across two seasons, YZ16 showed generally comparable performance for key yield-related traits.

Powdery mildew resistance in YZ16 is conferred by the Pm4 allele on chromosome arm 2AL and can be efficiently tracked using a functional marker. Together with resistance at both seedling and adult stages generally competitive agronomic performance under the tested conditions, YZ16 represents a valuable donor for marker-assisted selection and resistance gene pyramiding in wheat breeding.