| Résumé | Wheat leaf rust, caused by Puccinia triticina Erikss., is one of the most common and damaging diseases of wheat in Canada and throughout the world. To understand the P. triticina population virulence analysis of the population in Canada has been conducted annually for over 80 years. The virulence profile of the P. triticina population and virulence to key resistance genes changes significantly over time, and differs between regions. Recently, genetic analysis via DNA sequencing of representative isolate from the P. triticina populations from 2018 to 2022 initially revealed three diverse groups in Canada. All isolates within group one had the same two mating type alleles, group two isolates all had a second combination of alleles, whereas group three isolates were partitioned into eight subgroups encompassing different genetic clades. A fourth distinct group was later found from British Columbia. To combat leaf rust, the resistance genes Lr2a, Lr13, Lr14a, Lr16, Lr21, and Lr34 have been used extensively in Canadian spring wheat cultivars. Lr34, Lr46, and Lr67 are unique among resistance genes in that they are non-race-specific, conditioning partial resistance to all isolates, while also providing resistance to other wheat diseases. Critically, Lr34 and Lr67 were demonstrated to confer resistance to Fusarium head blight. The complete picture underlying Lr34 functions is not fully understood, but only Lr34res lines accumulate the fungistatic compound 1-O-p-coumaroyl-3-O-feruloylglycerol. Lr34 also produces leaf tip necrosis; this is enhanced at low temperatures. Combinations of race-specific leaf rust resistance genes, with Lr34, Lr46, and/or Lr67, have the best potential to protect wheat from a dynamic Canadian leaf rust population. |
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