Division of Environmental Science and Ecological Engineering, College of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
Mycopathologia. 2010 May;169(5):403-12. doi: 10.1007/s11046-010-9272-y. Epub 2010 Jan 27.
Downy mildew is an economically important and widespread disease in quinoa (Chenopodium quinoa) growing areas. Although in many studies Peronospora farinosa is most commonly regarded as the causal agent of the disease, identification and classification of the pathogen remain still uncertain due to its taxonomic confusion. Thirty-six Peronospora isolates from quinoa with different geographic origins including Argentina, Bolivia, Denmark, Ecuador, and Peru were morphologically and molecularly compared with Peronospora species from other Chenopodium species. The morphology of three herbarium specimens was similar to that of P. variabilis, which originated from C. album, characterized by flexuous to curved ultimate branchlets and pedicellated conidia. Phylogenetic analysis based on ITS rDNA sequences also placed the quinoa pathogen within the same clade as P. variabilis. Within the ITS rDNA sequences of the quinoa pathogens, two base substitutions were found, which separated the majority of the Danish isolates from isolates from South America, but no sequence difference was found among the isolates from different cultivars of quinoa. The present results indicate that the pathogen responsible for the quinoa downy mildew is identical to Peronospora variabilis and that it should not be lumped with P. farinosa as claimed previously by most studies.
霜霉病是藜麦（Chenopodium quinoa）种植区一种具有重要经济意义且广泛发生的病害。尽管在许多研究中，被孢霉（Peronospora farinosa）最常被认为是该病的致病因子，但由于其分类上的混淆，对病原体的鉴定和分类仍然存在不确定性。本研究从藜麦的不同地理起源（包括阿根廷、玻利维亚、丹麦、厄瓜多尔和秘鲁）中获得了 36 个被孢霉分离物，对其进行了形态学和分子学比较，这些分离物与来自其他藜麦物种的被孢霉物种有关。三个标本的形态与来自 C. album 的 P. variabilis 相似，其特征为弯曲至弯曲的最终小枝和具柄的分生孢子。基于 ITS rDNA 序列的系统发育分析也将藜麦病原菌置于与 P. variabilis 相同的分支中。在藜麦病原菌的 ITS rDNA 序列中发现了两个碱基替换，这将丹麦的大多数分离物与来自南美洲的分离物分开，但在不同藜麦品种的分离物之间没有发现序列差异。本研究结果表明，引起藜麦霜霉病的病原菌与 P. variabilis 相同，不应像大多数研究之前所主张的那样，将其与 P. farinosa 归为一类。
