Volatiles from wasabi inhibit entomopathogenic fungi: Implications for tritrophic interactions and biological control

Abstract

When wasabi plants are damaged by plant pathogens or herbivores they produce volatile allyl isothiocyanate (AITC) as a defense mechanism. In the current study, we conducted experiments to determine whether volatiles from damaged wasabi leaves or synthetic AITC also have negative effects on the beneficial entomopathogenic fungi, Beauveria bassiana sensu lato (Balsamo) Vuillemin and Isaria fumosorosea Wize, which contribute to regulation of a major pest of wasabi, the striated white butterfly, Pieris melete Ménétriès. Conidial germination of both fungi was inhibited when exposed to volatiles from macerated wasabi leaves; the concentration of AITC in the volatiles was also quantified. The inhibitory activity of macerated wasabi leaves was compared with that of synthetic AITC, demonstrating that the inhibitory effect of wasabi volatiles was due to the presence of AITC. These results indicate that AITC released from damaged wasabi leaves has the potential to inhibit fungal infection of insect pests in wasabi fields.