Nested Association Mapping in Oat (Avena Sativa L.) Identifies the Location of Multiple Genes Conferring Resistance to the Crown Rust Pathogen Puccinia Coronata f. sp. Avenae

Abstract Oat crown rust, caused by the fungus Puccinia coronata f. sp. avenae (Pca), is the most destructive foliar pathogen of oat. Almost 100 genes conferring resistance to Pca have been catalogued. However, only limited genes have been mapped, and the chromosomal location of most remains undetermined. The goals of this study were to detect the chromosomal locations of 13 catalogued Pc genes and one uncharacterized but highly effective resistance gene and to identify functions related to them. We used an A. sativa L. nested association mapping population comprising 14 biparental F2:3 families, derived from crosses between a donor carrying Pca resistance and the Pca susceptible variety ‘Swan’. A total of 2,356 F2:3 lines were phenotyped for response to pathotypes of Pca, from which the final AsNAM population of 707 individuals were selected. Based on DArT-Seq genotype data were identified 15,940 high-quality single nucleotide polymorphisms. Using the IBD mixed model, eight resistance QTL to Pca with varying phenotypic variance were identified. The locations of four previously mapped genes were confirmed (Pc38, chr7D; Pc45, chr2D; Pc46, chr3D; Pc50, chr3D), and two genes were mapped for the first time (Pc36, chr1C; Pc70, chr5D). The results revealed some families had a single dominant gene controlling resistance, while others had more complex resistance. Several genes were linked or allelic (Pc13, Pc46, and Pc50 on chr3D; Pc36 and Pc60 on chr 1C; Pc38 and Pc64 on chr 7D). 31 putative genes belonging to eight protein families related with disease resistance were identified in detected QTL regions.