Abstract

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.

摘要

茎锈病是全球大麦、燕麦和小麦作物的主要病害。控制的主要手段是宿主抗性基因，这些基因被整合到商业品种中，并且对大多数禾本科 Puccinia graminis Pers. 的致病菌种有效。由于这种病原体不断变异，因此分析种群毒力结构对于检测毒力增加的新种族至关重要。2015 年至 2019 年从加拿大马尼托巴省、安大略省、魁北克省和萨斯喀彻温省收集茎锈病样本，以发现大麦 ( Hordeum vulgare L.)、燕麦 ( Avena sativa L.) 和小麦 ( Triticum小麦L.) 场和两个病原体种群的毒力动态。栽培小麦中不存在茎锈病，大麦和燕麦田中的发病率在所有年份中都处于痕量 (<1%) 水平。而P. graminis f.的优势种。sp. 小麦是MCCDC（54.5％）和TPMKC（27.3％），2015年和TMRTF（29.2％）在2016年，比赛QFCSC是占主导地位的2017年（52.0％），2018（88.4％），2019年（81.3％）。P. graminis f.的优势种。sp. avenae是 2015 年到 2018 年的 TJS。种族 TJS 的频率逐年下降，从 89.5%（2015 年）到 73.7%（2016 年）、42.6%（2017 年）、49.1%（2018 年），2019 年只有 14.3%。 2019 年的主导种族是 SGB (51.7%) 和 TGN (19.6%)。P. graminis f. 的一个新种（TJQ）。sp.2016 年在马尼托巴省 Emerson 附近的一个地点检测到了avenae，这可能是由于TJS 种族对Pg15的单步突变导致的无毒。