QTL Mapping of Oat Crown Rust Resistance in Australian Fields and Identification of a Seedling Resistance Locus in Oat Line GS7

The development of oat cultivars with resistance to crown rust caused by Puccinia coronata f. sp. Avenae (Pca) is key for sustainable disease control. This study examined two recombinant inbred line populations, Provena x GS7 and Boyer x GS7, to identify adult plant resistance QTL in Australian fields. Seven distinct QTL associated with rust resistance were identified. KASP markers were developed for single nucleotide polymorphisms (SNPs) tightly linked to the four most significant QTL on chromosomes 4A and 7A. A major QTL named QPc_GS7_4A.2 with a resistance allele derived from line GS7 was mapped to chromosome 4A, overlapping with genomic regions previously associated with both resistance gene Pc61 and adult plant resistance. Genetic mapping for rust resistance at the seedling stage using a subset of Provena x GS7 lines with contrasting alleles at QPc_GS7_4A.2 suggests a role of this locus in seedling resistance, which may be explained by the presence of Pc61. Seedling resistance profiles between GS7 and the Pc61 differential line against 20 Pca isolates, a haplotype analysis of QPc_GS7_4A.2 in the oat crown rust differential set, and a collection of 182 oat lines support this hypothesis, although confirmation needs future research. The KASP markers developed in this study will assist breeders in efficiently integrating the resistance allele for gene combinations in new cultivars.