Grabke Anja, Fernández-Ortuño Dolores, Schnabel Guido
School of Agricultural, Forest and Environmental Sciences, Clemson University, Clemson SC 29634.
Plant Dis. 2013 Feb;97(2):271-276. doi: 10.1094/PDIS-06-12-0587-RE.
Botrytis cinerea, the causal agent of gray mold disease, is one of the most important pathogens of strawberry. Its control in commercial strawberry fields is largely dependent on the application of fungicides during bloom and fruit maturation. The hydroxyanilide fenhexamid is one of the most frequently used fungicides in the southeast of the United States for gray mold control. It inhibits the 3-ketoreductase (Erg27) of the ergosterol biosynthesis pathway and, due to this site-specific mode of action, is at risk for resistance development. Single-spore isolates were collected from 11 commercial strawberry fields in North and South Carolina and subjected to a conidial germination assay that distinguished sensitive from resistant phenotypes. Of the 214 isolates collected, 16.8% were resistant to fenhexamid. Resistance was found in three of four locations from North Carolina and in four of seven locations from South Carolina, indicating that resistance was widespread. Mutations in Erg27 (T63I, F412S, F412C, and F412I) were associated with resistance, with F412S the predominant and most widespread mutation. In this study, mutations T63I and F412C in field isolates of B. cinerea are described for the first time. Detached fruit studies showed that field rates of Elevate 50 WDG (fenhexamid) controlled sensitive but not resistant isolates carrying any of the four mutations. Resistant isolates produced the same lesion size and number of sporulating lesions on fruit sprayed with Elevate 50 WDG as on untreated controls, showing the fungicide's loss of efficacy against those isolates. A rapid polymerase chain reaction method was developed to quickly and reliably distinguish isolates sensitive or resistant to fenhexamid in the Carolinas and to determine the mutation associated with resistance. The presence of fenhexamid-resistant strains in B. cinerea from strawberry fields in the Carolinas must be considered in future resistance management practices for sustained gray mold control.
灰葡萄孢是灰霉病的病原菌，是草莓最重要的病原体之一。在商业草莓田中对其进行防治很大程度上依赖于在花期和果实成熟期施用杀菌剂。羟基苯胺类的咯菌腈是美国东南部最常用于防治灰霉病的杀菌剂之一。它抑制麦角甾醇生物合成途径中的3-酮还原酶（Erg27），由于这种位点特异性作用方式，存在产生抗性的风险。从北卡罗来纳州和南卡罗来纳州的11个商业草莓田中收集单孢分离株，并进行区分敏感和抗性表型的分生孢子萌发试验。在所收集的214个分离株中，16.8%对咯菌腈具有抗性。在北卡罗来纳州的四个地点中有三个发现了抗性，在南卡罗来纳州的七个地点中有四个发现了抗性，这表明抗性已广泛存在。Erg27中的突变（T63I、F412S、F412C和F412I）与抗性相关，其中F412S是主要且分布最广的突变。在本研究中，首次描述了灰葡萄孢田间分离株中的T63I和F412C突变。离体果实研究表明，50%咯菌腈水分散粒剂（咯菌腈）的田间施用量能控制敏感分离株，但不能控制携带四种突变中任何一种的抗性分离株。抗性分离株在喷施50%咯菌腈水分散粒剂的果实上产生的病斑大小和产孢病斑数量与未处理对照相同，表明该杀菌剂对这些分离株失去了药效。开发了一种快速聚合酶链反应方法，以快速可靠地区分卡罗来纳州对咯菌腈敏感或抗性的分离株，并确定与抗性相关的突变。在卡罗来纳州草莓田的灰葡萄孢中存在咯菌腈抗性菌株，在未来持续防治灰霉病的抗性管理实践中必须予以考虑。
