College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China; State & Local Joint Engineering Research Center of Green Pesticide Invention and Application, Nanjing 210095, China.
College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
Pestic Biochem Physiol. 2019 Jan;153:95-105. doi: 10.1016/j.pestbp.2018.11.006. Epub 2018 Nov 9.
Target leaf spot caused by Corynespora cassiicola is an economically important foliar disease on cucumber. In recent years, this disease has caused a serious problem on greenhouse-cultivated cucumber in China. In this study, to explore the characteristics and possible causes of heavy occurrence of the disease, we monitored the resistance of C. cassiicola strains from different provinces of China to benzimidazole and quinone outside inhibitor (QoI) fungicides. The results from sequence comparison of target genes β-tubulin and Cytb of 619C. cassiicola strains indicate that resistance frequency to benzimidazoles and QoIs is up to 100%. Furtherly, molecular resistance mechanism of C. cassiicola to benzimidazoles and QoIs was analysed. One single mutation E198A and three double mutations E198A&M163I, E198A&F167Y and E198A&F200S were observed in target gene β-tubulin, which confers resistance to benzimidazoles. To our knowledge, this is the first report that double mutations of β-tubulin confer resistance to benzimidazoles in filamentous fungi. Compared with single mutation E198A, three double mutations significantly decreased sensitivity to benzimidazoles. Moreover, significant difference of sensitivity to benzimidazoles was observed among three double mutations. These mutation genotypes of β-tubulin have different geographical distribution and the mutation E198A&M163I is prevalent, occupying for 63.94%. In addition, strong cross resistance patterns between carbendazim, benomyl and thiabendazole were observed in C. cassiicola strains conferring different β-tubulin mutations. For QoI resistance, the only mutation G143A of Cytb was detected in tested 619C. cassiicola strains. Strong positive cross resistance was observed when comparing the EC values of sensitive and resistant strains of C. cassiicola for six intrinsically different QoIs such as azoxystrobin, fluoxastrobin, pyraclostrobin, fenaminstrobin, picoxystrobin and coumoxystrobin. Taken together, all the results not only provide novel insights into understanding resistance mechanism to benzimidazoles and QoIs in filamentous fungi, but also provide some important references for resistance management of target leaf spot on cucumber.
由壳二孢菌（Corynespora cassiicola）引起的靶斑病是黄瓜上一种重要的叶部病害。近年来，该病在中国温室栽培的黄瓜上造成了严重问题。在这项研究中，为了探讨该病严重发生的特点和可能原因，我们监测了来自中国不同省份的壳二孢菌菌株对苯并咪唑类和线粒体呼吸抑制剂（QoI）类杀菌剂的抗性。对 619 株壳二孢菌靶标基因β-微管蛋白和 Cytb 的序列比较结果表明，对苯并咪唑类和 QoI 类的抗性频率高达 100%。进一步分析了壳二孢菌对苯并咪唑类和 QoI 类的分子抗性机制。在靶标基因β-微管蛋白中观察到一个单一突变 E198A 和三个双突变 E198A&M163I、E198A&F167Y 和 E198A&F200S，这些突变赋予了对苯并咪唑类的抗性。据我们所知，这是首次报道丝状真菌中的双突变β-微管蛋白赋予对苯并咪唑类的抗性。与单一突变 E198A 相比，三个双突变显著降低了对苯并咪唑类的敏感性。此外，三个双突变之间的苯并咪唑类敏感性存在显著差异。这些β-微管蛋白的突变基因型具有不同的地理分布，突变 E198A&M163I 最为流行，占 63.94%。此外，在赋予不同β-微管蛋白突变的壳二孢菌菌株中，观察到了对多菌灵、苯菌灵和噻菌灵的强烈交叉抗性模式。对于 QoI 抗性，在所测试的 619 株壳二孢菌菌株中仅检测到 Cytb 的唯一突变 G143A。当比较敏感和抗性菌株对 6 种不同内在 QoI（如唑菌胺酯、氟唑菌酰胺、吡唑醚菌酯、肟菌酯、苯氧菌酯和肟醚菌胺）的 EC 值时，观察到强烈的正交叉抗性。总的来说，这些结果不仅为理解丝状真菌对苯并咪唑类和 QoI 类的抗性机制提供了新的见解，也为防治黄瓜靶斑病提供了一些重要的参考。
