Seedling resistance to Puccinia coronata f. sp. avenae in Avena strigosa , A . barbata and A . sativa

A study was carried out in which seedling resistance to the crown rust pathogen, Puccinia coronata f. sp. avenae ( Pca ), was characterised among 385 oat accessions of Avena strigosa , A . barbata and A . sativa from the USDA-ARS National Small Grains Collection. Accessions were tested with eight Australian pathotypes of Pca of diverse pathogenicity on a series of differential genotypes carrying known seedling resistance genes. Three diploid accessions, CIav2524, PI78821 and PI83721 of A . strigosa , were highly resistant to all eight Pca pathotypes, and were postulated to carry Pc50 and Pc68 , Pc91 , or one or more new resistance genes. A total of 58 unidentified resistance specificities were detected among the tetraploid A . barbata accessions. All 58 resistances were ineffective against at least one of the Pca pathotypes and could therefore be novel. Additionally, evidence was obtained for the presence of genes Pc39 and Pc52 (in A . barbata and A . sativa accessions), Pc45 (in A . barbata accessions), Pc94 (in A . strigosa and A . barbata accessions) and the “Saia” resistance (in A . strigosa accessions).