Virulence phenotypes of Puccinia graminis on barley, wheat and oat in Canada from 2020 to 2022

Stem rust of barley and wheat is caused by the obligate pathogen Puccinia graminis f. sp. tritici (Pgt) and stem rust of oat is caused by P. graminis f. sp. avenae (Pga). Stem rust can be a very destructive disease of cereal crops and, until the development of resistant host varieties, was responsible for millions of dollars of losses to producers. Genetic host resistance is the most common and effective method to control stem rust on cereals. Knowledge of the virulence genes and races present in the pathogen population is important to identify effective host resistance genes for use by cereal plant breeders. The objectives of this study were to determine the incidence and severity of P. graminis in wheat, barley and oat in Manitoba, Canada, and assess the virulence frequencies and races of isolates collected from Manitoba, Saskatchewan and Ontario, Canada during 2020 to 2022. Stem rust incidence and severity was very light in Manitoba in 2020, 2021 and 2022. Virulence was not observed on resistance genes Sr30, Sr24 and Sr31 from Canadian collections of Pgt isolates made during 2020 to 2022. Race QFCSC was the most common race of Pgt in Canada, and races MCCFC and TPMKC were also common in Manitoba in 2022. Virulence to resistance genes Pg6, Pg10 and Pg16 was not observed among Pga isolates. The most common race of Pga from Manitoba and Saskatchewan was TGN, followed by SGB and TJS. The most frequent Pga races were TDJ, TDD and TGN in Ontario.