Identification of a novel Pm65 allele conferring a wide spectrum of resistance to powdery mildew in wheat accession PI 351817.

Powdery mildew is caused by the most adaptive biotrophic fungus Blumeria graminis f. sp. tritici (Bgt) inflicting wheat worldwide. Novel powdery mildew resistance genes are urgently needed. PI 351817 is a German cultivar exhibiting a wide spectrum of resistance to Bgt isolates collected from different wheat-growing regions of the United States. Evaluation of an F2 population and 237 F2:3 lines derived from OK1059060-2C14 × PI 351817 for responses to Bgt isolate OKS(14)-B-3-1 identified a single, dominant gene, designated Pm351817, for powdery mildew resistance in PI 351817. Using bulked segregant analysis (BSA) and simple sequence repeat (SSR) markers, Pm351817 was mapped in the terminal region of the long arm of chromosome 2A. Deep sequencing of the genotyping-by-sequencing libraries of the two parental lines identified a set of single nucleotide polymorphism (SNPs) markers in the 2AL candidate gene region. Those SNP markers was subsequently converted to Kompetitive Allele specific PCR (KASP) markers for genotyping the mapping population. Linkage analysis delimited Pm351817 to a 634-kb interval between Stars-KASP656 (771,207,512 bp) and Stars-KASP662 (771,841,609 bp) on 2AL based on the Chinese Spring reference sequence IWGSC RefSeq v2.0. Tests of allelism indicated Pm351817 is located at the Pm65 locus. Pm351817 shows resistance to all Bgt isolates used in this study and can be used to enhance powdery mildew resistance in the United States. KASP markers flanking Pm351817 can be used to select Pm351817 in wheat breeding programs after further tests for polymorphism.