A pilot study of antifungal and chemosensitizing activities of two microbial metabolites to assess their applicability in organic crop production as potential biologicals controlling some Fusarium fungi

Abstract

Chemosensitization of phytopathogenic fungi to synthetic fungicides is a promising technology that could enable disease control using reduced fungicidal dosages while maintaining the requested antifungal effect through combining of fungicides and sensitizers, i. e., compounds that synergistically enhance the efficacy of reduced dosages. Usage of biogenic sensitizers, which are non-toxic or marginally toxic to fungi, aligns with sustainable agriculture principles. Earlier we demonstrated that a microbial metabolite, 6-demethylmevinolin (6-DMM), mildly inhibited the growth of Fusarium fungi and synergistically enhanced the sensitivity of other fungi to a triazole fungicide Folicur^®. Another microbial metabolite, tacrolimus (FK-506), was reported to improve the action of some medical triazols. Given these data, we explored the growth inhibitory effect of FK-506 and 6-DMM towards several strains of Fusarium graminearum and F. culmorum, and evaluate their chemosensitizing activity for these species using a checkerboard assay. FK-506 was found to demonstrate high strain-specific fungitoxicity, and the species-selective chemosensitization, while 6-DMM exhibited moderate fungitoxicity and looked more promising as the sensitizer of both species. Several 6-DMM/Folicur^® combinations were revealed that synergistically enhanced Folicur^® effect, multiplying the fungicidal impact of its low doses. At the most effective synergistic ratios, the efficacy of the combined treatments almost doubled the additive effect.