Suppressive efficacy of volatile compounds produced by Bacillus mycoides on damping-off pathogens of cabbage seedlings

Rhizoctonia solani Kühn and Pythium aphanidermatum Edson cause cabbage seedling damping-off, resulting in severe yield losses. The current study demonstrates the production of toxic volatile organic compounds (VOCs) by two strains of Bacillus mycoides and the evaluation of a potential use of B. mycoides as a biocontrol agent to control cabbage damping-off. Two VOCs, dimethyl disulphide and ammonia, were found to reduce radial growth, cause hyphal deformation and result in organelle degeneration in both R. solani and P. aphanidermatum. Pathogen hyphae, after being exposed to VOCs, showed poor rigidity, shrinkage, curling and swelling. The amount of VOCs produced by B. mycoides and the antagonistic activity against plant pathogens varied, depending on the type of medium used to culture bacteria. Application of B. mycoides cell suspensions to cultivation medium promotes growth of five different plant species tested. Experiments conducted in greenhouses revealed that B. mycoides did not reduce damping-off incidence caused by R. solani. However, B. mycoides reduced damping-off incidence induced by P. aphanidermatum by as much as 45% on cabbage seedlings. The results provide valuable information on the feasibility of utilizing B. mycoides as a biocontrol agent in controlling cabbage damping-off.