Anthracnose fruit rot is one of the main diseases affecting strawberries especially in warm and humid climates. In commercial settings, producers are relying on fungicides to control the disease. One of the most potent chemical classes of fungicides for anthracnose control are the quinone outside inhibitors (QoIs), but resistance in field isolates due to a point mutation in the target gene cytb has recently been reported in multiple states of the USA. During a routine screening, two Colletotrichum nymphaeae isolates (OH_S1 and OH_S2) obtained from strawberry plants of a commercial field in Marietta-Ohio were found to be resistant to QoI fungicide azoxystrobin. The EC50 values determined in poison agar tests were greater than 100 μg/L. Both isolates were not controlled on detached strawberry fruit treated with label rates of Abound fungicide (a.i. azoxystrobin) and revealed disease severity of 86% and 96% on detached fruit. A baseline isolate (Cn_ebel2) of the same species revealed an EC50 value of 1.2 μg/L and no disease developed on Abound-treated fruit. In contrast to other reports, sequencing of the cytb gene from all three isolates used in this study revealed no amino acid changes in cytb, indicating the existence of a different and still unknown resistance mechanism.

中文翻译：

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从草莓中分离到的抗外抑制剂的睡衣炭疽菌中的醌缺乏 cytb 基因突变

炭疽病果实腐烂是影响草莓的主要病害之一，尤其是在温暖潮湿的气候中。在商业环境中，生产者依靠杀菌剂来控制疾病。用于炭疽病控制的最有效的化学杀菌剂类别之一是醌外抑制剂 (QoI)，但最近在美国多个州报告了由于靶基因 cytb 中的点突变而导致的田间分离株的耐药性。在常规筛选过程中，发现从玛丽埃塔-俄亥俄州一个商业领域的草莓植物中获得的两种睡衣炭疽菌分离物（OH_S1 和 OH_S2）对 QoI 杀菌剂嘧菌酯具有抗性。在毒琼脂试验中测定的 EC50 值大于 100 μg/L。在用 Abound 杀菌剂（ai 嘧菌酯）并揭示了离体果实的病害严重程度分别为 86% 和 96%。同一物种的基线分离株 (Cn_ebel2) 显示 EC50 值为 1.2 μg/L，并且在 Abound 处理的果实上未发生疾病。与其他报告相反，本研究中使用的所有三个分离株的 cytb 基因测序显示 cytb 中没有氨基酸变化，表明存在不同且仍然未知的抗性机制。