Spatiotemporal Distribution, Mechanisms, and Field Efficacy of Tebuconazole Resistance in Blumeria graminis f. sp. tritici (Bgt) Populations in Hebei, Henan, and Shandong Provinces, China.

The wheat powdery mildew fungus Blumeria graminis f. sp. tritici (Bgt) is a devastating pathogen for wheat production in the core wheat-producing regions of China, including Hebei, Henan, and Shandong provinces. The demethylation inhibitor fungicide tebuconazole has been a cornerstone for Bgt management. However, its intensive and prolonged application has led to the development of resistance, reducing its field efficacy. This study presents findings on the spatiotemporal dynamics of tebuconazole resistance in Bgt populations across these provinces, reveals the resistance mechanisms, and describes applications for sustainable resistance management. The sensitivity of Bgt populations to tebuconazole in China's major wheat-producing regions gradually decreased from 2007 to 2024. Despite the absence of highly resistant isolates, the frequency of moderately resistant isolates increased over time, exceeding 40% by 2020. Compared with sensitive isolates, resistant isolates exhibited greater ecological fitness, evidenced by superior pathogenicity, sporulation capacity, and competitive ability, suggesting that they could become dominant in wheat fields. The resistance mechanisms of Bgt to tebuconazole are attributed to multiple mechanisms, including target-site CYP51 gene mutations, enhanced efflux pump activity, and upregulation of detoxification enzymes such as glutathione S-transferase and cytochrome P450 monooxygenase. Field trials revealed that tebuconazole applied alone exhibited poor control efficacy against wheat powdery mildew. In contrast, its combination formulations with fungicides of different modes of action, such as fluazinam-tebuconazole and cyflufenamid-tebuconazole, maintained significantly better control efficacy. Understanding the spatiotemporal distribution, resistance mechanisms, and field efficacy of tebuconazole against Bgt is crucial for developing effective resistance management strategies and optimizing chemical control measures.