Races of Puccinia graminis on barley, oat, and wheat in Canada in 2005.
Stem rust, caused by Puccinia graminis, is an important disease of cereal crops that is primarily controlled in Canada through cultivar resistance. Surveys of common barley (Hordeum vulgare), common oat (Avena sativa), and common wheat (Triticum aestivum) fields and trap nurseries were conducted to obtain incidence and severity information and to identify changes in virulence structure in the pathogen populations. Stem rust samples were collected in Saskatchewan, Manitoba, and Quebec in 2005. Stem rust was not found on cultivated wheat and was at trace levels in barley and oat fields. For the first time since surveys started in 1919, only one race (QFCSC) of P. graminis f. sp. tritici was found on wheat or barley in Canada. Eleven races of P. graminis f. sp. avenae were found in 2005. The predominant races from cultivated oat samples from Saskatchewan and Manitoba were TJJ (33% and 57%, respectively), TGB (39% and 12%), TJG (11% and 21%), and TGD (17% and 6%). The predominant races from wild oat samples from Saskatchewan and Manitoba were TGB (49% and 31%, respectively), TJJ (15% and 30%), TGD (12% and 25%), and TJD (17% and 4%). In Quebec, three races (CDJ, FDJ, and TDD) distinct from those in the Prairie region were found. Additionally, a new race of P. graminis f. sp. avenae (TJS) with virulence on the Pg-a resistance-gene complex and all single-gene differential lines except Pg6, Pg10, Pg11, and Pg16 was detected in Manitoba in 2005.