Races of Puccinia graminis on wheat, barley, and oat in Canada in 2004.
Stem rust, caused by Puccinia graminis, is capable of causing devastating losses in cereal crops. Surveys of fields and trap nurseries of barley (Hordeum vulgare), oat (Avena sativa), and wheat (Triticum aestivum) were conducted in Canada to provide incidence, severity, and virulence information on populations of P. graminis f. sp. tritici and P. graminis f. sp. avenae. Samples were collected in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, and Quebec in 2004. Stem rust was absent on commercial spring wheat cultivars and found at trace levels in barley and oat fields. Environmental conditions across the Prairie region were highly unfavorable for rust infection, with historically low temperatures and above-average precipitation. Only three races of P. graminis f. sp. tritici were detected in 2004, predominantly races QFCSR (67.3%) and TPMKR (30.9%). Nine races of P. graminis f. sp. avenae were detected in 2004. The predominant races on commercial oat were TJJ (54.3%), TGB (12.8%), TJG (11.7%), and TGD (8.5%). The predominant races on wild oat were TJJ (47.8%), TGD (18.3%), TGB (13.9%), and TJD (11.3%). The frequency of race TJJ, which is virulent on all oat cultivars in Canada, declined slightly after several years of steady increase in proportion in the P. graminis f. sp. avenae population. In Ontario, only race TDJ was detected (two samples). Race TLG, which is virulent on the Pg-a gene complex and was found in Manitoba in 2003, was detected at one location on wild oat in Saskatchewan in 2004.