First and eighth authors: Key Laboratory of Integrated Pest Management in Crops, Ministry of Agriculture, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China; second author: College of Chemical Engineering, Nanjing Forestry University, Nanjing, Jiangsu, 210037, China; third author: Department of Plant and Environmental Sciences, Clemson University, Clemson, SC 29634; fourth, fifth, and sixth author: Eukaryotic Pathogens Innovations Center and Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634; and seventh author: Key Lab of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan 430070, China and Department of Plant Pathology, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Phytopathology. 2018 Nov;108(11):1263-1275. doi: 10.1094/PHYTO-02-18-0054-R. Epub 2018 Sep 19.
Anthracnose disease, caused by Colletotrichum truncatum, affects marketable yield during preharvest production and postharvest storage of fruits and vegetables worldwide. Demethylation inhibitor (DMI) fungicides are among the very few chemical classes of single-site mode of action fungicides that are effective in controlling anthracnose disease. However, some species are inherently resistant to DMIs and more information is needed to understand this phenomenon. Isolates of C. truncatum were collected from the United States and China from peach, soybean, citrus, and begonia and sensitivity to six DMIs (difenoconazole, propiconazole, metconazole, tebuconazole, flutriafol, and fenbuconazole) was determined. Compared with DMI sensitive isolates of C. fructicola, C. siamense, and C. fioriniae (EC value ranging from 0.03 to 16.2 µg/ml to six DMIs), C. truncatum and C. nymphaeae were resistant to flutriafol and fenbuconazole (with EC values of more 50 µg/ml). Moreover, C. truncatum was resistant to tebuconazole and metconazole (with resistance factors of 27.4 and 96.0) and displayed reduced sensitivity to difenoconazole and propiconazole (with resistance factors of 5.1 and 5.2). Analysis of the Colletotrichum spp. genome revealed two potential DMI targets, CYP51A and CYP51B, that putatively encode P450 sterol 14α-demethylases. Both genes were identified and sequenced from C. truncatum and other species and no correlation between CYP51 gene expression levels and fungicide sensitivity was found. Four amino acid variations L208Y, H238R, S302A, and I366L in CYP51A, and three variations H373 N, M376L, and S511T in CYP51B correlated with the DMI resistance phenotype. CYP51A structure model analysis suggested the four alterations may reduce azole affinity. Likewise, CYP51B structure analysis suggested the H373 N and M376L variants may change the conformation of the DMI binding pocket, thereby causing differential sensitivity to DMI fungicides in C. truncatum.
炭疽病是由胶孢炭疽菌引起的，会影响水果和蔬菜在收获前生产和收获后储存期间的商品产量。脱甲基抑制剂 (DMI) 杀菌剂是少数几种有效控制炭疽病的单一作用位点杀菌剂化学类别之一。然而，有些物种天生对 DMIs 具有抗性，需要更多的信息来了解这种现象。从美国和中国的桃、大豆、柑橘和秋海棠中采集了胶孢炭疽菌的分离物，并测定了它们对 6 种 DMIs（咯菌腈、丙环唑、咪鲜胺、戊唑醇、氟环唑和苯醚甲环唑）的敏感性。与 DMI 敏感的胶孢炭疽菌、胶孢炭疽菌和胶孢炭疽菌（EC 值在 0.03 到 16.2 µg/ml 之间）相比，胶孢炭疽菌和胶孢炭疽菌对氟环唑和苯醚甲环唑具有抗性（EC 值大于 50 µg/ml）。此外，胶孢炭疽菌对戊唑醇和咪鲜胺具有抗性（抗性因子分别为 27.4 和 96.0），对咯菌腈和丙环唑的敏感性降低（抗性因子分别为 5.1 和 5.2）。对胶孢炭疽菌基因组的分析显示了两个潜在的 DMI 靶标，CYP51A 和 CYP51B，它们推测编码 P450 甾醇 14α-脱甲基酶。从胶孢炭疽菌和其他物种中鉴定并测序了这两个基因，但没有发现 CYP51 基因表达水平与杀菌剂敏感性之间的相关性。CYP51A 中的 4 个氨基酸变异 L208Y、H238R、S302A 和 I366L，以及 CYP51B 中的 3 个变异 H373N、M376L 和 S511T 与 DMI 抗性表型相关。CYP51A 结构模型分析表明，这 4 种改变可能降低唑类化合物的亲和力。同样，CYP51B 结构分析表明，H373N 和 M376L 变体可能改变 DMI 结合口袋的构象，从而导致胶孢炭疽菌对 DMI 杀菌剂的敏感性不同。
