The grapevine powdery mildew Erysiphe necator (E. necator) is an obligate pathogen. Powdery mildew-diseased vines show an important reduction in plant size, winter hardiness and grape yield. Even a low-level infection with powdery mildew was shown to taint wine and ultimately reduce wine quality. For many years, succinate dehydrogenase inhibitor (SDHI) fungicides, mainly the new generation active ingredients (AIs) boscalid, penthiopyrad and fluopyram, have been widely used to control powdery mildew in grapevines. The repeated use of fungicides (mainly boscalid) has resulted in the emergence of resistant microorganisms such as Botrytis cinerea (B. cinerea). However, boscalid resistance was never observed in E. necator. In this study, a large-scale survey of French grapevine field populations of E. necator revealed many field populations with low sensitivity to boscalid. Single spore strains originating from collected resistant populations showed Half maximal effective concentration (EC50) values greater than 100 mg L⁻¹, and strains originating from boscalid sensitive populations showed EC50 values lower than 1 mg L⁻¹. The complete nucleotide sequences of the EnSdhB succinate dehydrogenase of sensitive and resistant single spore strains revealed that H242R and H242Y substitutions in the EnSdhB succinate dehydrogenase subunit conferred E. necator resistance to boscalid. No cross-resistance of E. necator strains bearing H242R and H242Y substitutions in EnSdhB succinate dehydrogenase to fluxapyroxad and fluopyram was noticed. Therefore, our results highlight the emergence of resistance to boscalid activity in French vineyards and warrant the need of the implementation of risk assessment strategies to maintain effective grapevine protection against powdery mildew.

葡萄白粉病Erysiphe necator（E. necator）是专性病原体。白粉病病菌的藤本植物的大小，抗寒性和葡萄产量显着降低。即使是少量的白粉病感染也能污染葡萄酒，并最终降低葡萄酒质量。多年来，琥珀酸脱氢酶抑制剂（SDHI）杀菌剂，主要是新一代活性成分（AIs）的鳞片，戊硫吡喃德和氟吡草，已被广泛用于控制葡萄中的白粉病。重复使用杀真菌剂（主要是生物杀虫剂）导致出现了抗性微生物，如灰葡萄孢（B. cinerea）。但是，在大肠杆菌中从未观察到抗Boscalid的现象。在这项研究中，法国的葡萄田间种群的大规模调查E.钩虫揭示了许多领域的人群一起啶酰菌胺敏感性低。源自收集到的抗性种群的单孢子菌株的半数最大有效浓度（EC50）值大于100 mg L ^-1，源自鳞片鳞茎敏感种群的菌株的EC50值小于1 mg L ^-1。敏感和抗性单孢子菌株的EnSdhB琥珀酸脱氢酶的完整核苷酸序列显示，EnSdhB琥珀酸脱氢酶亚基中的H242R和H242Y取代赋予了E. necator对Boscalid的抗性。大肠杆菌无交叉抗性注意到在EnSdhB琥珀酸脱氢酶中带有H242R和H242Y取代的菌株可转化为fluxapyroxad和flupyyram。因此，我们的结果突显了法国葡萄园中对Boscalid活动的抗性的出现，并保证有必要实施风险评估策略，以保持有效的葡萄白粉病防霉保护。