Chemosensitization of to Chemical Fungicides Using Cyclic Lipopeptides Produced by Strain JCK-12.

Fusarium head blight (FHB) caused by infection with leads to enormous losses to crop growers, and may contaminate grains with a number of Fusarium mycotoxins that pose serious risks to human and animal health. Antagonistic bacteria that are used to prevent FHB offer attractive alternatives or supplements to synthetic fungicides for controlling FHB without the negative effects of chemical management. Out of 500 bacterial strains isolated from soil, JCK-12 showed strong antifungal activity and was considered a potential source for control strategies to reduce FHB. JCK-12 produces several cyclic lipopeptides (CLPs) including iturin A, fengycin, and surfactin. Iturin A inhibits spore germination of Fengycin or surfactin alone did not display any inhibitory activity against spore germination at concentrations less than 30 μg/ml, but a mixture of iturin A, fengycin, and surfactin showed a remarkable synergistic inhibitory effect on spore germination. The fermentation broth and formulation of JCK-12 strain reduced the disease incidence of FHB in wheat. Furthermore, co-application of JCK-12 and chemical fungicides resulted in synergistic antifungal effects and significant disease control efficacy against FHB under greenhouse and field conditions, suggesting that JCK-12 has a strong chemosensitizing effect. The synergistic antifungal effect of JCK-12 and chemical fungicides in combination may result from the cell wall damage and altered cell membrane permeability in the phytopathogenic fungi caused by the CLP mixtures and subsequent increased sensitivity of to fungicides. In addition, JCK-12 showed the potential to reduce trichothecenes mycotoxin production. The results of this study indicate that JCK-12 could be used as an available biocontrol agent or as a chemosensitizer to chemical fungicides for controlling FHB disease and as a strategy for preventing the contamination of harvested crops with mycotoxins.