Ecological functions of Trichoderma spp. and their secondary metabolites in the rhizosphere: interactions with plants

Trichoderma spp. are common soil and root inhabitants that have been widely studied due to their capacity to produce antibiotics, parasitize other fungi and compete with deleterious plant microorganisms. These fungi produce a number of secondary metabolites such as non-ribosomal peptides, terpenoids, pyrones and indolic-derived compounds. In the rhizosphere, the exchange and recognition of signaling molecules by Trichoderma and plants may alter physiological and biochemical aspects in both. For example, several Trichoderma strains induce root branching and increase shoot biomass as a consequence of cell division, expansion and differentiation by the presence of fungal auxin-like compounds. Furthermore, Trichoderma, in association with plant roots, can trigger systemic resistance and improve plant nutrient uptake. The present review describes the most recent advances in understanding the ecological functions of Trichoderma spp. in the rhizosphere at biochemical and molecular levels with special emphasis on their associations with plants. Finally, through a synthesis of the current body of work, we present potential future research directions on studies related to Trichoderma spp. and their secondary metabolites in agroecosystems.