Virulence of Puccinia striiformis f. sp. tritici, cause of stripe rust on wheat, in western Canada from 1984 to 2002

Abstract

Fifty-seven isolates of Puccinia striiformis f. sp. tritici, causing stripe rust on wheat, were collected in western Canada from 1984 to 2002. The virulence of these isolates was tested on the 17 World and European differentials as well as 7 supplemental differentials. Thirty-nine races were identified. Before 2000, races virulent on wheat ‘Lee’ (Yr7, Yr22, Yr23) and ‘Owens’ mainly originated from Creston, British Columbia, while most of the races from the prairies were avirulent on these two cultivars. New races detected in Canada since 2000 were virulent on both ‘Compair’ (Yr8, Yr19) and ‘Clement’ (Yr9, YrCle). Race 33 (238E150) was repeatedly detected from 2000 to 2002, and other new races had a virulence spectrum that was similar to that of race 33. Some of the prevalent races of stripe rust in the prairie provinces were also detected in the Creston area of British Columbia, suggesting a possible link in the source of inoculum between these two areas. None of the races were virulent on Triticum spelta var. album (Yr5). ‘Chinese 166’ (Yr1), ‘Moro’ (Yr10, YrMor), ‘Hybrid 46’ (Yr3b, Yr4b), Triticum dicoccoides selection G-25 (Yr15), and ‘Spalding Prolific’ (YrSP) were resistant to more than 90% of the races detected in western Canada, and all of them were resistant to the new races detected since 2000. Climatic conditions and cultivar resistance play an important role in the survival and propagation of these races on the Canadian prairies.