Physiological and Molecular Signalling Involved in Disease Management Through Trichoderma: An Effective Biocontrol Paradigm

Abstract

Biological control or biocontrol is the use of specific microorganisms that interfere with plant pathogens and pests, and sustain organisms useful to human. It is a nature-friendly, ecological approach to overcome the problems caused by standard chemical methods of plant protection which drastically affect the environment as well as consumer. Trichoderma, a member of ascomycota was first described by Pearson (1794) and its beneficial activities as a biocontrol agent (BCA) has been known since 1930 and since then there have been extensive efforts to use them for plant disease control. Trichoderma species play an important role in controlling fungal plant pathogens, especially the soil borne pathogens, by competing for nutrients and space, producing cell wall degrading enzymes (CWDE) or through mycoparasitism (the direct attack of one fungus on another). They are not only fungal parasites but can also produce antibiotics. These processes such as the production of antifungal metabolites and hydrolytic enzymes are mediated by G-proteins and mitogen activated protein (MAP) kinases. In addition, certain strains can release a variety of compounds that induce systemic and localized resistance response in host plant, mediated by alteration in plant gene expression. This Trichoderma mediated induced systemic resistance (ISR) is regulated by various plant hormones like jasmonic acid (JA), ethylene (ET), abscisic acid (ABA), gibberellic acid (GA) and salicylic acid (SA). Among them, JA, ET and SA are the central players in defence signalling. Thus, Trichoderma encompasses different mechanisms to achieve effective disease control against a variety of plant pathogens by means of various signalling components and pathways. Another approach for improving resistance against pathogens is to express genes of Trichoderma in plants, through genetic manipulation. Recently, there has been increasing attempt in development of transgenic plants using genes from Trichoderma spp. which are responsible for biocontrol activity. Besides protecting against biotic stress, root-colonization with Trichoderma also enhances growth and productivity of host plant by improving nutrient and water uptake. Due to the effective control of plant pathogens/diseases and improvement of plant growth, several Trichoderma bioproducts are now available commercially. However, much work still needs to be done to explore its full potential for improving plant growth and managing plant diseases.