Synergistic antifungal activity of methyl salicylate and 2,3-butanedione against Rhizopus stolonifer: membrane disruption mechanism and control of postharvest soft rot.

BACKGROUND: Postharvest soft rot caused by Rhizopus stolonifer results in severe economic losses globally. Current control strategies rely heavily on synthetic fungicides, raising environmental and food safety concerns. This study evaluated the synergistic antifungal potential of methyl salicylate (MeSA) combined with 2,3-butanedione, nerol, clove essential oil, or oregano essential oil, and elucidated the underlying antifungal mechanism. RESULTS: Screening via the co-toxicity factor method revealed that the combination of MeSA (41.7 μL L-1) and 2,3-butanedione (37.4 μL L-1) exhibited significant synergism (F = 34.59), allowing for reduced dosages while maintaining high efficacy. In vivo assays demonstrated that this combination (83.4 and 74.8 μL L-1) significantly suppressed disease incidence, reducing soft rot rates to 11.11% in figs and 8.33% in tomatoes, while markedly inhibiting lesion expansion in peaches and green peppers. Mechanistically, the treatment compromised R. stolonifer viability by disrupting membrane integrity and permeability, inducing oxidative stress and mitochondrial dysfunction, which ultimately triggered apoptosis. CONCLUSION: The combination of MeSA and 2,3-butanedione offers a potent, eco-friendly bio-rational strategy for managing postharvest soft rot, presenting a viable alternative to conventional synthetic fungicides for fruit preservation. © 2026 Society of Chemical Industry.