Biofumigation with carvacrol disrupts membrane integrity and metabolic homeostasis in yam leaf spot pathogen Alternaria alternata.

Alternaria alternata, a devastating fungal pathogen responsible for leaf spot diseases and postharvest rot across over 380 plant species, poses significant agricultural threats worldwide. Carvacrol, a plant-derived phenolic compound, exhibits robust antifungal properties, yet its biofumigation efficacy and molecular mode of action against A. alternata remain poorly characterized. A 2023-2024 survey in Henan and Shandong provinces of China identified A. alternata as the dominant pathogen causing yam leaf spot disease. This study systematically evaluated the antifungal efficacy of carvacrol against A. alternata through biofumigation, demonstrating potent inhibition with an IC of 3.83 mg/L, which was significantly lower than its direct contact IC. Carvacrol disrupted mycelial morphology, causing irregular branching, septation, and significantly reduced sporulation and germination. Mechanistically, carvacrol impaired membrane integrity via lipid peroxidation and induced cytoplasmic leakage. Metabolic disruptions included DNA fragmentation and reduced carbohydrate and pyruvate metabolism. Transcriptomic analysis identified 1528 differentially expressed genes, highlighting downregulation in glycolysis, tryptophan metabolism, and secondary metabolite pathways. Molecular docking simulations confirmed strong binding affinities between carvacrol and key enzymes, including cytochrome P450, kynureninase, and indoleamine 2,3-dioxygenase. In planta assays validated carvacrol's efficacy, achieving 97.88 % protective and 97.81 % curative inhibition of yam leaf spot. These findings elucidate carvacrol's multi-target antifungal mechanisms, emphasizing dual disruption of metabolic pathways and membrane stability, and highlights its potential as a sustainable, broad-spectrum biofumigant in eco-friendly disease management strategies.