Mapping of the Oat Crown Rust Resistance Gene Pc39 Relative to Single Nucleotide Polymorphism Markers.

Crown rust, caused by Puccinia coronata f. sp. avenae Eriks. (Pca), is among the most important oat diseases resulting in significant yield losses in many growing regions. A gene-for-gene interaction is well established in this pathosystem and has been exploited by oat breeders to control crown rust. Pc39 is a seedling crown rust resistance gene that has been widely deployed in North American oat breeding. DNA markers are desired to accurately predict the specific Pc genes present in breeding germplasm. The objectives of the study were as follows: (i) to map Pc39 in two recombinant inbred line (RIL) populations (AC Assiniboia/MN841801 and AC Medallion/MN841801) and (ii) to identify single nucleotide polymorphism (SNP) markers for postulation of Pc39 in oat germplasm. Pc39 was mapped to a linkage group consisting of 16 SNP markers, which placed the gene on linkage group Mrg11 (chromosome 1C) of the oat consensus map. Pc39 cosegregated with SNP marker GMI_ES01_c12570_390 in the AC Assiniboia/MN841801 RIL population and was flanked by the SNP markers avgbs_126086.1.41 and GMI_ES15_c276_702, with genetic distances of 1.7 and 0.3 cM, respectively. In the AC Medallion/MN841801 RIL population, similar results were obtained but the genetic distances of the flanking markers were 0.4 and 0.4 cM, respectively. Kompetitive Allele-Specific PCR assays were successfully designed for Pc39-linked SNP loci. Two SNP loci defined a haplotype that accurately predicted Pc39 status in a diverse panel of oat germplasm and will be useful for marker-assisted selection in oat breeding.