Biocontrol of Botrytis cinerea by chitin-based cultures of Paenibacillus elgii HOA73

Abstract

The chitinase-producing bacterium, Paenibacillus elgii HOA73, is a biocontrol agent that limits the damage caused to plants by microbial pathogens, insects, and nematodes. However, the mechanisms involved in the biocontrol of plant diseases by HOA73 have not been determined. The objective of this study was to elucidate the role of extracellular chitinase obtained from isolate HOA73 in the control of the fungal pathogen Botrytis cinerea, the causative agent of gray mold in tomato. The HOA73 strain grew efficiently in a chitin-containing broth and produced chitin oligomers through chitinase activity; protease, lipase, and Fe-chelating siderophores were also secreted by the bacterium. Cultures containing intact bacteria inhibited B. cinerea conidia germination to a greater extent than did the bacterial cells alone or the cell-free culture supernatant. The antifungal activity increased with culture age and was heat-sensitive because of chitinase-mediated production of long-chain chitin oligomers. The biocontrol efficacy of undiluted bacterial cultures against gray mold in tomato was comparable to that of a standard fungicide. This study demonstrated that P. elgii HOA73 bacterial cultures grown on chitin-based minimal medium may be an effective formulation for the integrated control of gray mold.