Antimicrobial compounds produced by bacteria have been increasingly acknowledged as an important resource for the control of phytopathogens. We used a bioassay-guided fractionation approach to identify antifungal metabolites produced by two avocado rhizobacteria (INECOL-4742 and INECOL-5927), both members of the Bacillus subtilis/B. amyloliquefaciens species complex, against Fusarium solani and F. kuroshium, causal agent of Fusarium dieback in avocado and other hosts. The butanol (BuOH) organic extract from INECOL-4742 (B1-Bu) exhibited the highest percentage of inhibition (PI) against F. solani (78.76 %), also inhibiting F. kuroshium by up to 44.30 %. Primary fractions, Bu-F3, Bu-F12 and Bu-F15, obtained by silica gel open column chromatography, exhibited the highest PI against F. solani (28.57 % to 33.50 %) and F. kuroshium (38.78 % to 45.00 %). The presence of cyclic lipopeptides from the iturin, surfactin and fengycin families in B1-Bu extracts and primary fractions was determined by UPLC-ESI-HRMS. The Confocal Laser Microscopy analysis revealed deformations in the hyphae of F. kuroshium exposed to extracts, primary fractions and C-13 surfactin chemical standard. These results emphasize the potential of natural products from Bacillus for the control of the emerging phytopathogenic fungus F. kuroshium.
Keywords: Fusarium dieback; Fusarium kuroshium; antifungal agents; cyclic lipopeptides; surfactants.
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