INCIDENCE AND VIRULENCE OF PUCCINIA-GRAMINIS F SP TRITICI ON WHEAT AND BARLEY IN CANADA IN 1991

Stem rust was first observed in barley in southern Manitoba on June 11 , which is about 4 weeks earlier than normal. A severe epidemic of ste m rust on barley was expected, but losses remained light in 1991. Stem rust also developed poorly on susceptible lines of wheat in the unifo rm nurseries. Heavy rains and cool weather in late June and early July appear to have limited development of stem rust. Four races were iden tified from 514 isolates of Puccinia graminis f. sp. tritici obtained from wheat, cultivated barley (Hordeum vulgare), and wild barley (H. j ubatum). From Ontario/Quebec, races TPM (51.6%), QFC (35.5%), and QCC (12.9%) were isolated from wheat; races QCC (55.6%), QFC (22.2%), and TPM (22.2%) from cultivated barley. From Manitoba and Saskatchewan, ra ces QCC (33.5%), TPM (32.6%), QFC (26.4%), and RCR (7.4%) were isolate d from wheat; races QCC (98.1%), TPM (1.3%), and QFC (0.6%) from culti vated barley; and races QCC (65.8%), TPM (23.7%), QFC (7.9%), and RCR (2.6%) from wild barley. From Alberta, races QFC (45.9%), TPM (27.0%), QCC (24.3%), and RCR (6.1%) were isolated from wheat; and race QCC (1 00%) from cultivated barley. All isolates from all sources were virule nt to genes Sr5, Sr21, Sr9g, and Sr17. No virulence was detected to re sistance genes Sr6, Sr13, Sr2Z Sr24, Sr25, Sr26, Sr27, Sr29, Sr30, Sr3 1, Sr32, or Sr37.