Characterization of an antifungal compound produced by Bacillus sp. strain A5F that inhibits Sclerotinia sclerotiorum

Abstract

A potential antagonist, Bacillus sp. strain A5F was isolated from soybean rhizosphere following in vitro dual plate screening. The bacterium displayed strong inhibitory activity in vitro against soybean stem rot pathogen, Sclerotinia sclerotiorum. The culture supernatant of strain A5F completely suppressed the mycelial growth of the pathogen, indicating that suppression was due to the presence of antifungal compounds in the culture filtrate. The culture filtrate also suppressed other phytopathogenic fungi including Fusarium oxysporum and Macrophomina phaseolina, in vitro suggesting a broad spectrum antagonistic activity against fungal pathogens. Chemical extraction followed by chromatographic analysis resulted in two antifungal fractions. The high resolution-electron spin ionization-mass spectrometry (HR-ESI-MS) and Nuclear Magnetic Resonance (1D and 2D1H) spectra of these antifungal fractions revealed the presence of antifungal compounds, one of which showed similarity to bacillomycin D. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.