Shared weapons in fungus-fungus and fungus-plant interactions? Volatile organic compounds of plant or fungal origin exert direct antifungal activity in vitro

Fungi emit a diverse blend of volatile organic compounds (VOCs) that mediate multiple fungus-fungus interactions. Plants emit VOCs as well, which can serve as resistance-inducing signals but might also act as direct resistance agents. We screened 22 VOCs that are emitted from infected plants for putative inhibitory effects on three fungal phytopathogens: Colletotrichum lindemuthianum, Fusarium oxysporum and Botrytis cinerea. The growth of all three fungi was significantly inhibited when the mycelia were exposed to an atmosphere containing nonanal, (+)-carvone, citral, trans-2-decenal, L-linalool, or nerolidol. Eugenol completely inhibited the growth of all three fungi, and 1-octen-3-ol, nonanal, 2,6-dimethyl-2,4,6-octatriene, citral, α-terpineol and trans-2-decanal inhibited at least one fungus completely. Most of these VOCs are also emitted from fungi. We conclude that antagonistic fungus-fungus and plant-fungus interactions might share common mechanisms and that plant VOCs can function as resistance agents that fungal pathogens must overcome for successful infection.