Suppressive efficacy of volatile compounds produced byBacillus mycoideson damping-off pathogens of cabbage seedlings

Abstract

AbstractRhizoctonia solaniKühn andPythium aphanidermatumEdson 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 ofBacillus mycoidesand the evaluation of a potential use ofB.mycoidesas 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 bothR. solaniandP. aphanidermatum. Pathogen hyphae, after being exposed to VOCs, showed poor rigidity, shrinkage, curling and swelling. The amount of VOCs produced byB. mycoidesand the antagonistic activity against plant pathogens varied, depending on the type of medium used to culture bacteria. Application ofB.mycoidescell suspensions to cultivation medium promotes growth of five different plant species tested. Experiments conducted in greenhouses revealed thatB. mycoidesdid not reduce damping-off incidence caused byR.solani. However,B. mycoidesreduced damping-off incidence induced byP. aphanidermatumby as much as 45% on cabbage seedlings. The results provide valuable information on the feasibility of utilizingB. mycoidesas a biocontrol agent in controlling cabbage damping-off.