Positive Role of Trichoderma harzianum in Increasing Plant Tolerance to Abiotic Stresses: A Review

As a beneficial fungus, Trichoderma harzianum (T. harzianum) has been widely applied for growth promotion and biocontrol. Recently, it has attracted much attention with regard to improving stress tolerance in plants under abiotic stress. In this paper, the multiple mechanisms of T. harzianum for alleviating abiotic stress damage in plants are reviewed. T. harzianum can regulate the synthesis of key phytohormones, such as abscisic acid (ABA), indole-3-acetic acid (IAA), etc., thereby enhancing the physiological response ability of plants under stress conditions such as drought, salt stress, and high temperature. These are associated with antioxidant system regulation in plants, which reduces levels of reactive oxygen species (ROS) and oxidative damage and maintains intracellular redox balance. T. harzianum can also improve plant nutrient uptake and root development, secondary metabolism, soil environment and structure, and expression of related genes. In addition, in this paper, the characteristics of T. harzianum application in field and horticultural crops are summarized and compared, revealing differences in the methods, concentrations, time, and effects of applying T. harzianum to various crops. We further explore the synergistic regulation effect of T. harzianum and plant–microbiome interaction on the stress microenvironment. Future perspectives on the molecular mechanism of T. harzianum and its field application potential are discussed. This review provides a theoretic and practical reference for the application of T. harzianum in agricultural production.