Genetic Mapping of the Powdery Mildew Resistance Gene Pm13 on Oat (Avena sativa) Chromosome 1D

Powdery mildew, caused by the biotrophic fungus Blumeria graminis DC. f. sp. avenae, is a widespread disease of oats, especially in the temperate regions of Western and Central Europe, and the use of resistant varieties is the most sustainable way to ensure stable yields. Therefore, the identification of robust and effective resistance to powdery mildew is of great interest for oat breedinpg. In contrast to race-specific resistance genes, adult plant resistance (APR) is generally considered to be more durable. The oat variety ‘Firth’, as well as related varieties such as ‘Husky’ or ‘Flämingstip’, contains an unknown APR gene, which was previously located on chromosome 1D using DArT markers. The aim of this study was to confirm and refine the chromosomal location of this resistance gene, tentatively named Pm13. To this end, two independent experiments were carried out using different genetic material under natural infection conditions in the field: genome-wide association mapping (GWAS) in a diverse set of 250 oat lines grown in 10 environments and QTL mapping in a HuskyxAVE1284 biparental population grown in three environments. Both approaches identified a QTL for powdery mildew resistance on the distal end of chromosome 1D in the hexaploid Sang oat genome. The locus explained up to 15% of the phenotypic variance in GWAS and 64% of the phenotypic variance in QTL mapping. Comparison of field data with results from laboratory leaf segment tests confirmed that Pm13 does indeed confer APR. The sequence information of the identified linked markers may allow the development of molecular markers useful for early selection of oat lines with high levels of APR.