Demonstration of biofumigation activity of Muscodor albus in soil substrates

The fungus M. albus has been shown to inhibit or kill other microbes in vitro and to control postharvest diseases by the production of a mixture of volatile compounds. While M. albus also controls soil-borne diseases, its biofumigation activity in soil substrates was never demonstrated. To demonstrate the role of volatiles in the control of damping-off, pots containing soil or soilless mix infested with Rhizoctonia solani were placed in closed plastic containers in the presence of active rye culture of M. albus without physical contact. After 48 h, the pots were taken out of the containers and planted with broccoli seeds. Exposing pots with infested soil substrates to the volatiles completely controlled damping-off. In subsequent experiments, PDA cultures of R. solani and Penicillium expansum were killed when placed for 48 h in closed containers with pots filled with soil or soilless mix treated with M. albus culture. Furthermore, significant quantities of isobutyric acid, a major M. albus volatile associated with antifungal activity, were detected in the headspace of these containers. The production of isobutyric acid in soil was several-fold higher than in soilless mix and persisted longer, peaking at 48 h. It is concluded that biofumigation activity occurs in soil substrates and is a major factor in the control of soil-borne diseases by M. albus.