Abstract Crown rust, caused by Puccinia coronata Corda var. avenae f. sp. avenae (Urban & Markova) (Pca), can negatively impact oat (Avena sativa L.) production in South Africa and little is known about pathogenic variability and cultivar response. Pca infected leaves were obtained from oat trial plots, commercial fields and wild oat (Avena spp.) during the 2016 and 2017 growing seasons for race analysis. Uncharacterised collections from 1998 to 2005 were also included. Single pustule isolates were derived from field collections and used for race typing on 16 international differential lines. Six races were identified from 88 isolates pathotyped with race JBLL originating from wild oat samples, SGLL, SQPL and SSTL from commercial oat samples and SBLL+ from both wild and commercial oat samples. Isolates collected in 1998 typed as races SBLL and SBLL+ and the 2005 isolates as race SQPL. Race SBLL was not detected in the 2016 and 2017 samples with SBLL+ being dominant during 2016–17. This is the first report of South African races with virulence for the resistance genes Pc38, Pc58 and Pc59. Seedling infection types of 70 additional oat lines and cultivars to the described races showed incompatible phenotypes for 27 entries. Field data revealed moderate to high levels of adult plant resistance for a few cultivars to races SBLL+ and SSTL. Genetic analysis of 31 isolates, including two USA control isolates, revealed three genetic lineages. No apparent correlation was observed among year of collection, geographic origin, phenotype and genotype of isolates except for race JBLL that originated from wild oat collections in the Western Cape.

中文翻译：

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Puccinia coronata var avenae f. 的发生和致病性。sp. 南非燕麦上的燕麦

摘要 冠锈病，由 Puccinia coronata Corda var. 引起。阿韦纳 f. sp. 燕麦 (Urban & Markova) (Pca) 会对南非的燕麦 (Avena sativa L.) 生产产生负面影响，并且对致病变异性和品种反应知之甚少。在 2016 年和 2017 年生长季节期间，从燕麦试验地、商业田和野燕麦（Avena spp.）中获得了受 Pca 感染的叶子，用于种族分析。还包括 1998 年至 2005 年的无特征收藏。单个脓疱分离株来自野外采集，用于 16 个国际差异系的种族分型。从 88 个分离株中鉴定出 6 个小种，其致病型为来自野燕麦样品的 JBLL 小种，来自商业燕麦样品的 SGLL、SQPL 和 SSTL，以及来自野生和商业燕麦样品的 SBLL+。1998 年收集的分离株分类为 SBLL 和 SBLL+ 种，2005 年收集的分离株分类为 SQPL 种。在 2016 年和 2017 年的样本中未检测到种族 SBLL，其中 SBLL+ 在 2016-17 年期间占主导地位。这是南非种族对抗性基因 Pc38、Pc58 和 Pc59 具有毒力的第一份报告。70 个额外的燕麦品系和品种的幼苗感染类型对所描述的种族显示出 27 个条目的不相容表型。田间数据显示，一些栽培品种对 SBLL+ 和 SSTL 小种具有中等至高水平的成株抗性。对 31 个分离株（包括两个美国对照分离株）的遗传分析揭示了三个遗传谱系。除了源自西开普省野生燕麦收集的 JBLL 种族外，在分离物的收集年份、地理来源、表型和基因型之间没有观察到明显的相关性。