Searching for Novel Oat Crown Rust Resistance in Diploid Oat Avena strigosa Schreb. Reveals the Complexity and Heterogeneity of the Analyzed Genebank Accessions

Crown rust, one of the most destructive diseases of oat, regularly occurs worldwide and leads to significant yield losses. The constant evolution of the Puccinia coronata f. sp. avenae pathogen causes a rapid decline in the effectiveness of currently used crown rust resistance genes, so new ones are urgently needed. In this study, 39 accessions of Avena strigosa Schreb. from ten countries gathered from the Polish National Genebank were evaluated at the seedling stage for crown rust reaction using a detached leaf assay and five isolates of P. coronata with diverse virulence profiles. Ten plants of each accession were tested, and 28 diverse infection profiles (IPs) were defined. One hundred and sixty-eight out of 390 plants revealed an IP of unidentified resistance. Thirty-eight (97%) of the accessions studied showed a heterogeneous infection pattern, none of the accessions displayed homogeneous susceptibility, and one (51887) was homogeneously resistant to all races used. The obtained results confirmed the complexity and heterogeneity of the accessions gathered in the genebanks. A. strigosa preserved as complex populations could be a valuable source of resistance to crown rust and potentially other pathogens. The variability of the analyzed populations was ascertained by a detailed diversity analysis of the transformed resistance/susceptibility data. The averaged resistance rating for the genebank specimens available in the databases may be an obstacle in revealing the beneficial alleles of genes hidden among the plants representing accessions preserved as complex populations. Potential donors of effective resistance may be discovered even in accessions with general susceptibility, which is a promising alternative at a time when making new collections of wild and weedy accessions is under threat from agricultural practice and climate change.