Volatile organic compounds emitted by Trichoderma: Small molecules with biotechnological potential

Trichoderma species have been widely used in agriculture as biocontrol agents and plant growth promoters. Specialized metabolites, formerly secondary metabolites, are essential for Trichoderma's bioactivity. From these, volatile organic compounds (VOCs) emitted by Trichoderma have multiple functions in plant protection, including enhancing plant growth, modulating root architecture, and activating plant defenses against biotic and abiotic stresses. Also, the blend of VOCs produced by Trichoderma species inhibits plant pathogenic microorganisms. Emission of different Trichoderma VOCs occurs when these fungi are growing separately or during interaction with plants and microbes. Diverse systems, such as inverted and split plates, and hermetic boxes for adult plants, have been used to examine the impact of Trichoderma-emitted VOCs during interactions with plants or other microbes. The emission of VOCs produced by Trichoderma depends on various factors including the fungus's species, its age and culture medium, and the time of interaction with other organisms. A biostimulant effect on plants was achieved applying pure and commercial volatile compounds, identified in the mixtures of VOCs emitted by Trichoderma species. This review describes the current knowledge on the VOCs generated by Trichoderma species, particularly during the Trichoderma-plant and Trichoderma-fungi interactions.