The potential biocontrol agent Paenibacillus polymyxa TP3 produces fusaricidin-type compounds involved in the antagonism against gray mold pathogen Botrytis cinerea.

Paenibacillus polymyxa is a beneficial bacterium for plant health. Paenibacillus polymyxa TP3 exhibits antagonistic activity toward Botrytis cinerea and alleviates gray mold symptoms on the leaves of strawberry plants. Moreover, suppression of gray mold on the flowers and fruits of strawberry plants in field trials, including vegetative cells and endospores, was demonstrated, indicating the potential of strain TP3 as a biological control agent. To examine the anti-B. cinerea compounds produced by P. polymyxa TP3, matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry was performed and fusaricidin-corresponding mass spectra were detected. Moreover, fusaricidin-related signals appeared in imaging mass spectrometry of TP3 when confronted with B. cinerea. By using liquid chromatography-mass spectrometry-based molecular networking approach, several fusaricidins were identified including a new variant of m/z 917.5455 with serine in the first position of the hexapeptide. Via advanced mass spectrometry and network analysis, fusaricidin-type compounds produced by P. polymyxa TP3 were efficiently disclosed and were presumed to play roles in the antagonism against gray mold pathogen B. cinerea.