Wheat nurseries and fields throughout Canada were surveyed annually, from 2020 to 2023, for the presence of leaf rust, caused by Puccinia triticina Erikss. Infected leaves were collected, then single pustule isolates were analyzed for virulence on a set of 16 differential lines. In 2020 there were 29 unique virulence phenotypes found among 230 isolates, in 2021 there were 37 unique virulence phenotypes found from 153 isolates, in 2022, 47 unique phenotypes were found among 246 isolates, and there were 69 unique phenotypes among 384 isolates in 2023. The most common virulence phenotypes over this 4-year period from Manitoba and Saskatchewan were MNPS, TNBJ, MBDS and MLPS. In Ontario these were TCTS, MBTN and TBRD, while in Quebec these were MBTN, TCTS, MBPS and TBSJ. The smaller samples from Ontario and Quebec were more diverse than the larger samples from Manitoba and Saskatchewan. There were only 25 isolates analyzed from British Columbia, but four of the five unique virulence phenotypes found there, LBDS, LCDS, CCPN and NBDS, were not found in the rest of Canada during this period. Only eight isolates from Alberta were analyzed and they were similar to virulence phenotypes found in Manitoba and Saskatchewan. The frequencies of virulence to Lr9, Lr24 and Lr21 were higher in Manitoba and Saskatchewan than in Ontario and Quebec, though the reverse was true for Lr2a, Lr2c and Lr18. When representative isolates were tested on additional differential lines there was no virulence detected to Lr19, Lr29, Lr32, Lr52 and Lr22a.
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