Mechanisms of Trichoderma–Mediated Plant Growth Promotion: From Metabolites to Plant Responses

The transition toward sustainable agriculture has driven the use of plant growth-promoting microorganisms as viable alternatives to conventional agrochemicals. Among these, species of the genus Trichoderma have emerged as pivotal players due to their ability to establish beneficial and complex interactions with plants that extend far beyond their traditional role as biocontrol agents. This review integrates recent advances in understanding the mechanisms by which Trichoderma promotes plant growth and development. Specifically, the evolutionary transition of Trichoderma from a mycoparasitic lifestyle to beneficial plant associations is examined, together with the molecular processes involved in plant recognition, root colonization, and establishment within the rhizosphere and plant tissues. Furthermore, the mechanisms through which Trichoderma enhances plant performance are addressed, including metabolite production (both volatile and non-volatile), phytohormone modulation, nutrient acquisition and mobilization, and enhanced photosynthetic capacity. Finally, current agricultural applications, the technical challenges of formulation and field implementation, and future perspectives on Trichoderma-based microbial consortia and precision agriculture tools are analyzed. Overall, this review provides a comprehensive framework highlighting the potential of Trichoderma as a premier biostimulant for modern sustainable farming.