Evaluating the Effects of Volatile Organic Compounds Emitted by Biological Control Agent Trichoderma: Their Impact on Plant Growth and Development

Members of one of the most frequently isolated genera of free-living soil fungi, Trichoderma, are well studied for their ability to reduce plant disease, promote plant growth and productivity. Previously, we demonstrated that T. viride emitted volatile organic compounds (VOCs) which induced growth promotion in the plant model system, Arabidopsis thaliana. The purpose of this study was to further examine and evaluate the effects of VOCs from several species of Trichoderma including: T. aggressivum, T. asperellum, T. atroviride, T. brevicompactum, T. harzianum, T. longibrachiatum, T. pseudokoningii, T. virens and T. viride (total of 22 strains) on A. thaliana and economically important crop, Lycopersicum esculentum. Plants and fungi were grown together while physically separated, allowing only gas exchanges to occur. Plants exposed to VOCs of several species of Trichoderma exhibited growth promotion and developmental changes including larger leaf size, increased shoot weight, increased lateral root branching, and increased total chlorophyll concentration. Real-Time qRT-PCR data shows that several auxin-related genes encoding efflux carrier, IAA, and SAUR-like proteins in A. thaliana were affected by the exposure to Trichoderma VOCs. Using CG-MS, we have identified over a hundred unique compounds emitted by Trichoderma: hydrocarbons, sesquiterpenes, terpenes, straight-chain alkenes, saturated and unsaturated alcohols, aldehydes, ketones, aromatic compounds, and heterocyclics. Of the 35 compounds tested using Arabidopsis, we have identified several compounds that induce plant growth.  Currently, we are studying the effects of individual VOCs on plant growth and conducting a transcriptome study by using RNA-Seq and bioinformatics tools to understand volatile-mediated plant-fungus interactions.