Races of Puccinia graminis on barley, oat, and wheat in Canada from 2015 to 2019
Fetch, T., Mitchell Fetch, J., Zegeye, T., Xue, A. (2021). Races of Puccinia graminis on barley, oat, and wheat in Canada from 2015 to 2019. Canadian Journal of Plant Pathology, [online] 43(3), 463-471. http://dx.doi.org/10.1080/07060661.2020.1829066
Plain language summary
Stem rust is a major disease on barley, oat, and wheat crops in Canada. Currently we control stem rust using resistant cultivars. However, new strains (races) of stem rust evolve and can migrate into Canada. Thus, it is necessary to conduct research to identify the races that are present in Canada to ensure Canadian producers are protected from rust epidemics. Collections were made from 2015 to 2019 in Manitoba, Ontario, Quebec, and Saskatchewan to determine how much stem rust infection was present and identify the races. Stem rust infection was at trace (<1%) levels in barley and oat fields and absent in cultivated wheat from 2015-2019. The most common races were MCCDC (54.5%) and TPMKC (27.3%) in 2015, and TMRTF (29.2%) in 2016, while race QFCSC was dominant in 2017 (52.0%), 2018 (88.4%), and 2019 (81.3%) on wheat and barley crops. These races do not present a danger to Canadian producers. Race TJS was dominant in oat crops from 2015-2018, but declined in frequency across the years, from 89.5% (2015) to 73.7% (2016), 42.6% (2017), 49.1% (2018), and only 14.3% in 2019. Race TJS is virulent on all Canadian oat varieties. The dominant races in 2019 were SGB (51.7%) and TGN (19.6%). (at 57% and 75%, respectively) in both years. It is unknown what caused this change, but these races are not virulent on resistant Canadian oat varieties. One new race (TJQ) was found in 2016 near Emerson, MB. While new highly virulent stem rust races have been reported in Africa and Sicily recently, none have been detected in Canada that would threaten wheat or barley production.
Stem rust is a major disease on barley, oat, and wheat crops worldwide. The primary means of control is by host resistance genes that are incorporated into commercial varieties and have been effective against most races of Puccinia graminis Pers., the causal pathogen. Since this pathogen continually mutates, analyzing the population virulence structure is crucial to detect new races with increased virulence. Stem rust samples were collected from 2015 to 2019 from the Canadian provinces of Manitoba, Ontario, Quebec, and Saskatchewan to find the prevalence of stem rust in barley (Hordeum vulgare L.), oat (Avena sativa L.), and wheat (Triticum aestivum L.) fields and the virulence dynamics in the two pathogen populations. Stem rust was absent in cultivated wheat and at trace (<1%) levels of incidence in barley and oat fields in all years. While the dominant races of P. graminis f. sp. tritici were MCCDC (54.5%) and TPMKC (27.3%) in 2015, and TMRTF (29.2%) in 2016, race QFCSC was dominant in 2017 (52.0%), 2018 (88.4%), and 2019 (81.3%). The dominant race of P. graminis f. sp. avenae was TJS from 2015 to 2018. Race TJS declined in frequency across the years, from 89.5% (2015) to 73.7% (2016), 42.6% (2017), 49.1% (2018), and only 14.3% in 2019. The dominant races in 2019 were SGB (51.7%) and TGN (19.6%). One new race (TJQ) of P. graminis f. sp. avenae was detected in 2016 at one location near Emerson, Manitoba, which may have arisen from a single-step mutation to avirulence to Pg15 from race TJS.