A novel antifungal peptide purified from Bacillus subtilis strain EDR4

Bacillus subtilis strain EDR4 is a potential biocontrol agent against Valsa mali (Vm), the fungus causing apple canker disease. In this study, we identified and characterized the antifungal peptide produced by B. subtilis EDR4. Peptides were isolated by 30% ammonium sulfate precipitation and purified by column chromatography. A 4-kDa peptide exhibiting antifungal activity was obtained and designated as P6. The amino acid sequence of P6 was determined by liquid chromatography combined with tandem mass spectrometry. P6 showed inhibitory effects against eight different pathogenic plant fungi, and was stable (i.e., retained its biological activity) at temperatures as high as 121?C for 20 min and at pH values ranging from 3 to 11. Microscopic examination of Vm hyphae treated with P6 showed protoplasm release, and in vitrospore germination was also inhibited. These results suggest that P6 is the active substance responsible for the antifungal activity of B. subtilisEDR4 against Vmand that P6 may be effective in the biocontrol of Vmas well as other plant pathogenic fungi.