Volatile organic compounds emitted from endophytic fungus Trichoderma asperellum T1 mediate antifungal activity, defense response and promote plant growth in lettuce (Lactuca sativa)

Trichoderma species are applied as biological control agents and biofertilizers to control plant diseases and enhance crop yields. The ability to inhibit pathogens, induce defense responses, and promote plant growth can result from the production of volatile organic compounds (VOCs). In this study, we evaluated the effects of VOCs from Trichoderma asperellum T1 on those multifaceted actions in lettuce. The VOCs released by T. asperellum T1 inhibited fungal growth of two leaf spot fungal pathogens, Corynespora cassiicola and Curvularia aeria. Lettuces responded to VOCs by increasing activities of the cell-wall degrading enzymes chitinase and beta-1,3-glucanase to 1.26 U mL(-1) and 4.45 U mL(-1), respectively, above those in the control. Accumulation of cell-wall degrading enzymes in lettuce that had been treated with VOCs resulted in morphological changes to fungal cell-walls. Exposure to the VOCs emitted by T. asperellum T1 significantly increased numbers of leaves and roots, plant biomass and total chlorophyll content in lettuce. Furthermore, GC/MS analysis revealed that T. asperellum T1 emitted 22 volatile compounds, which are involved in antifungal activity, inducing defense responses, and promoting growth in lettuce. (C) 2019 Elsevier Ltd and British Mycological Society. All rights reserved.