Antifungal activity mechanisms of venturicidin A against Botrytis cinerea contributes to the control of gray mould.

Background: Gray mould caused by Botrytis cinerea, an airborne phytopathogenic pathogen, infects many economically important fruits and vegetables. Secondary metabolic products of microorganisms are potential resources for developing fungicide alternatives. Venturicidin A (VentA) is produced by a biocontrol strain Streptomyces pratensis S10. Although a broad spectrum of antifungal activity has been reported for VentA, little is known about its antifungal mechanisms against B. cinerea.

Results: Venturicidin A exhibited a strong hyphal inhibition of B. cinerea with an EC₅₀ (effective concentration causing 50% growth inhibition) value of 1.08 μg mL^-1 on PDA medium. Different concentrations of VentA inhibited spore germination with an inhibition rate of 49-86%. Venturicidin A also displayed protective and curative activity against the development of B. cinerea infection on tomato fruit, reducing disease incidence by ≈28-78%. Additionally, VentA effectively reduced the disease index and lesion length of gray mould on tomato plant. Meanwhile, VentA downregulated the expression levels of six genes related to pathogenicity in B. cinerea. As observed by scanning electron microscopy, B. cinerea spores and hyphae are abnormal after treatment with VentA. Propidium iodide staining revealed that VentA destroyed cell membrane integrity, causing cytoplasmic leakage. Furthermore, VentA induced accumulation of reactive oxygen species and upregulated the genes encoding subunits for NADPH oxidase in B. cinerea.

Conclusion: This study indicated that VentA displayed strong inhibitory activity against B. cinerea and effectively reduced gray mould disease. Thus, VentA has the potential to manage gray mould caused by B. cinerea. © 2024 Society of Chemical Industry.