Characterization of an antifungal compound produced by Bacillus sp. strain A(5) F that inhibits Sclerotinia sclerotiorum.

A potential antagonist, Bacillus sp. strain A(5) F 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 A(5) F 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 2D(1) H) spectra of these antifungal fractions revealed the presence of antifungal compounds, one of which showed similarity to bacillomycin D.