Characterization of Pm65, a new powdery mildew resistance gene on chromosome 2AL of a facultative wheat cultivar.

Abstract

A new powdery mildew resistance gene that can be readily used in wheat breeding, Pm65, was identified in the facultative wheat cultivar Xinmai 208 and mapped to the terminal region of chromosome 2AL. Wheat powdery mildew, a widely occurring disease caused by the biotrophic fungus Blumeriagraminis f. sp. tritici (Bgt), poses a serious threat to wheat production. A high breeding priority is to identify powdery mildew resistance genes that can be readily used either alone or in gene complexes involving other disease resistance genes. An F2 population and 227 F2:3 families derived from the cross Xinmai 208 × Stardust were generated to map a powdery mildew resistance gene in Xinmai 208, a high-yielding Chinese wheat cultivar. Genetic analysis indicated that Xinmai 208 carries a single dominant powdery mildew resistance gene, designated herein Pm65, and linkage analysis delimited Pm65 to a 0.5cM interval covering 531.8Kb (763,289,667-763,821,463bp) on chromosome 2AL in the Chinese Spring reference sequence. An allelism test indicated that Pm65 is a new gene about 10.3cM distal to the Pm4 locus. Pm65 was 0.3cM proximal to Xstars355 and 0.2cM distal to Xstars356. It conferred near-immunity to 19 of 20 Bgt isolates collected from different wheat-growing regions of the USA. Coming from a high-yield potential cultivar, Pm65 can be directly used to enhance powdery mildew resistance in wheat. The newly developed SSR markers Xstars355 and Xstars356 have the potential to tag Pm65 for wheat improvement.