Molecular characterization of a powdery mildew resistance gene in wheat cultivar suwon 92.

ABSTRACT Powdery mildew, caused by Blumeria graminis f. sp tritici, is an important foliar disease of wheat worldwide. Pyramiding race-specific genes into a single cultivar and combining race-specific resistance genes with durable resistance genes are the preferred strategies to improve the durability of powdery mildew resistance. The objectives of this study were to characterize a powdery mildew resistance gene in Suwon 92 and identify gene-specific or tightly linked molecular markers for marker-assisted selection (MAS). A population of recombinant inbred lines (RILs) was derived by single seed descent from a cross between Suwon 92 and a susceptible cultivar, CI 13227. The RILs were screened for adult-plant infection type of powdery mildew and characterized with amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers. The linked markers explained 41.3 to 69.2% of the phenotypic variances measured in 2 years. A morphological marker, hairy glume, was also associated with powdery mildew resistance in Suwon 92, and explained 43 to 51% of the phenotypic variance. The powdery mildew resistance gene in Suwon 92 was located on the short arm of chromosome 1A where Pm3 was located. Two gene-specific markers were developed based on the sequence of the cloned Pm3b gene. These two markers, which were mapped at the same locus in the peak region of the LOD score for the RIL population, explained most of the phenotypic variance for powdery mildew resistance in the RIL population. The powdery mildew resistance in Suwon 92 is most likely conditioned by the Pm3 locus. The gene markers developed herein can be directly used for MAS of some of the Pm3 alleles in breeding programs.