Physiologic specialization of Puccinia graminis on wheat, barley, and oat in Canada in 2001

Abstract

Stem rust is an important disease of cereal crops that is primarily controlled in Canada through cultivar resistance. Annual stem rust surveys are conducted to provide early detection of novel races with virulence to currently grown cultivars and to identify changes in virulence frequency in the pathogen population. Stem rust samples were collected in Manitoba, eastern Saskatchewan, Ontario, and British Columbia in 2001. Stem rust was not found on cultivated wheat, but was found on commercial barley and oat fields in eastern Manitoba (trace to 20% severity) and in western Manitoba and eastern Saskatchewan (<5% severity). Some late-planted oat fields in the Red River Valley region of Manitoba had moderate to heavy (5%–40% severity) stem rust infection. Eight races of Puccinia graminis f. sp. tritici were found on wheat, seven on cultivated barley, and nine on wild barley. The predominant races on wheat and wild barley were RCRSK, QFCSR, and QCCJN. The predominant races on cultivated barley were QCCJN and RCCJN, which could threaten barley production. Eight races of Puccinia graminis f. sp. avenae were found on cultivated oat and five on wild oat. NA67 and NA29 were the predominant races on cultivated (57.6% and 15.8%) and wild (41.6% and 29.6%) oat, while NA76 increased to 14.4% on cultivated oat in 2001. NA67 and NA76 are virulent on all currently grown Canadian oat cultivars. A new race (NA77) avirulent to most oat cultivars was detected in Manitoba in 2001.