Armoracia rusticana, commonly known as horseradish, is a Brassicaceae condiment common in southern Brazilian cuisine. In 2020, plants with leaf lesions and white pustules were observed in a cultivation area in the metropolitan region of Curitiba, state of Paraná, Brazil. Based on phylogenetic studies, Albugo sensu lato was classified into the genera Albugo, Pustula, and Wilsoniana. As there is still no molecular characterization of the specimens that cause white rust in Brazil, this study aimed to identify the causal agent of white rust in A. rusticana. Symptomatic plants were collected to identify the oomycete and placed near asymptomatic plants for the pathogenicity test. Plants exposed to the diseased plants showed symptoms 14 days after exposure, while plants without exposure to diseased plants remained asymptomatic. Comparison of symptoms and morphology matched the characteristics of Albugo sensu lato. After morphometry and sequence comparison of the partial region of the cytochrome c oxidase subunit II (cox2) mtDNA gene, the oomycete was identified as Albugo rorippae. To date, this species is reported on A. rusticana, Rorippa amphibia, Rorippa palustris, and Rorippa sylvestris in Argentina, Australia, Germany, Czech Republic, Poland, and Romania. According to the literature, the Albugo specimens that colonize Armoracia sp. have low efficiency in colonizing Rorippa sp., and there are some differences in the oospores of the specimens isolated from these two hosts. Therefore, a comprehensive sampling of Albugo sp. in Armoracia and Rorippa species is essential to determine whether there is host genus specialization. This is the first report of A. rorippae in Armoracia rusticana in Brazil.

中文翻译：

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系统发育分析显示，在巴西，只有 Albugo rorippae 导致辣根出现白锈病


Armoracia rusticana，俗称辣根，是巴西南部美食中常见的十字花科调味品。2020 年，在巴西巴拉那州库里蒂巴大都会区的一个种植区观察到出现叶片病变和白色脓疱的植物。根据系统发育研究，Albugo sensu lato 被分为 Albugo、Pustula 和 Wilsoniana 属。由于在巴西仍没有引起白锈病的标本的分子特征，本研究旨在确定 A. rusticana 中白锈病的致病因素。收集有症状的植物以鉴定卵菌，并放置在无症状植物附近进行致病性测试。暴露于病植物的植物在暴露后 14 天出现症状，而未暴露于病植物的植物保持无症状。症状和形态学的比较与 Albugo sensu lato 的特征相匹配。经过对细胞色素 c 氧化酶亚基 II （cox2） mtDNA 基因部分区域的形态测量和序列比较，卵菌被鉴定为 Albugo rorippae。迄今为止，该物种在阿根廷、澳大利亚、德国、捷克共和国、波兰和罗马尼亚的 A. rusticana、Rorippa amphibia、Rorippa palustris 和 Rorippa sylvestris 上都有报道。根据文献，定植于 Armoracia sp. 的 Albugo 标本在 Rorippa sp. 定植效率低，并且从这两个宿主分离的标本的卵孢子存在一些差异。因此，对 Armoracia 和 Rorippa 物种中的 Albugo sp. 进行全面采样对于确定是否存在宿主属特化至关重要。这是巴西 Armoracia rusticana 中 A. rorippae 的首次报道。