Sublethal tebuconazole exposure enhances pathogenicity and resistance development in Sclerotium rolfsii.

BACKGROUND Tebuconazole, an exemplary triazole fungicide, was registered in China for controlling peanut southern blight (caused by Sclerotium rolfsii Sacc.) in 2025; however, mechanistic studies on its toxicological effects remain limited. This study evaluates tebuconazole's (EC10: 0.0029, EC25: 0.0099 and EC30: 0.0134 mg L-1) effects on S. rolfsii growth, virulence, antioxidant enzymes, and target gene expression to guide its scientific application. RESULTS Compared to the control, the sclerotia germination rate of S. rolfsii at 24 h was increased by 64.29, 89.34, and 71.43% under EC₁₀, EC₂₅, and EC₃₀ tebuconazole exposure treatments, respectively. The cell membrane permeability of S. rolfsii was reduced after 36 h of tebuconazole exposure; however, prolonged treatment disrupted membrane integrity and subsequently increased permeability. Sublethal tebuconazole exposure increases the virulence of S. rolfsii towards peanuts and promotes oxalic acid secretion. Antioxidant enzyme activities (superoxide dismutase, peroxidase and catalase) and expression of the target gene (SrCYP51) exhibit responsive activation under sublethal tebuconazole stress. CONCLUSION Tebuconazole (EC₁₀, EC₂₅, and EC₃₀) may induce sclerotial germination, enhance virulence, and upregulate expression of a target gene in S. rolfsii, which could pose threats to both effective disease control and fungicide resistance development in this pathogen. The results advance the understanding of tebuconazole toxicity against S. rolfsii and guide its control strategies. © 2025 Society of Chemical Industry.