Trichoderma: A Potent Fungus as Biological Control Agent

Abstract

Trichoderma species are free-living fungi that occur in nearly all the soils and other natural habitats. They can be easily isolated from soil and decomposing organic matter. The genus Trichoderma comprises a great number of fungal strains that act as biological control agents, the antagonistic properties of which are based on the activation of multiple mechanisms. A successful biocontrol system is one which is easy and economical to produce, safe, stable in the environment, and easily applied during the conventional agricultural practices. Biofungicides include in a broader sense fungicides of biological origin, i.e., botanical and microbial. The use of microbial fungicides as one of the major components of IPM is gaining acceptance, as these are generally specific, apparently harmless to the beneficial insects, animals, and human beings with no residue problems and environmental hazards. Microbial fungicides are made of microbes such as eco-friendly fungi. Trichoderma strains exert biocontrol against fungal phytopathogens either indirectly, by competing for nutrients and space, modifying the environmental conditions, or promoting plant growth and plant defensive mechanisms and antibiosis, or directly, by mechanisms such as mycoparasitism. These indirect and direct mechanisms may act coordinately and their importance in the biocontrol process depends on the Trichoderma strain, the antagonized fungus, the crop plant, and the environmental conditions, including nutrient availability, pH, temperature, and iron concentration. Activation of each mechanism implies the production of specific compounds and metabolites, such as plant growth factors, antibiotics, and carbon and nitrogen permeases. These metabolites can be either overproduced or combined with appropriate biocontrol strains in order to obtain new formulations for use in more efficient control of plant diseases and postharvest applications.