Evaluation of Avena spp. Accessions for Resistance to Oat Stem Rust

Oat stem rust, caused by Puccinia graminis f. sp. avenae, can cause significant yield losses in the eastern prairie region of western Canada. Currently, the predominant race of P. graminis f. sp. avenae in this region is NA67. Few genes confer resistance to NA67, and none are present in any oat cultivars registered for production in Canada. To detect lines exhibiting resistance to race NA67, we evaluated 9,978 accessions from 22 Avena spp. in field nurseries from 2001 to 2004. In all, 35 accessions were highly resistant and 12 were moderately resistant, comprised mostly of the species A. strigosa. Seventy-one accessions had an intermediate response, comprised mostly of A. abyssinica, A. barbata, A. sterilis, and A. vaviloviana. All other accessions (9,860 = 98.8%) were susceptible to race NA67. Some highly resistant accessions were found to have been incorrectly classified previously as hexaploid species A. sativa or A. sterilis, and were confirmed by chromosome counts to be diploid or tetraploid. The most promising source of novel stem rust resistance is from the diploid species A. strigosa. Transfer of resistance from diploid and tetraploid species to A. sativa is very difficult, but the lines identified in this study should prove useful as new sources of resistance to oat stem rust.