Mechanisms of action and biocontrol potential of Trichoderma against fungal plant diseases - A review

Plant diseases are among the major causes of the low productivity of crops, causing yield losses of up to 30%, heralding an enormous threat to global food security. Indiscriminate use of chemical-based fungicides for controlling fungal diseases has raised severe concerns about ecosystem health. Moreover, pathogens have become insensitive against these chemicals necessitating excessive use of chemicals for adequate control. The resulting accumulation of these chemicals in the food chain has provoked numerous health complications. For combating the adversaries of chemical-based fungicides, biological control of fungal pathogens is proposed as an eco-friendly alternative. Among various biological controls, Trichoderma-based biological control agents (BCAs) are widely used in agriculture for controlling soil-borne pathogens. These BCAs are commercialized and known as; stimulators of resistance in plants, growth enhancers, bio-fertilizers, and bio-pesticides. Biological management of plant pathogens has yielded valuable results in the sustainability of ecosystems and compelling improvements in the quality and quantity of agricultural produce. These BCAs exhibit potential against pathogens, remarkably improve photosynthesis, plant growth, and nutrient use efficiency for impressive crop yields. Despite these peculiarities, Trichoderma's mechanisms against pathogens and their growth promotional effects are not thoroughly investigated, hence formulating the prime objective of the current review. Along with these, Trichoderma-based fungicides marketed in different geographical locations are encompassed in this review. Finally, the knowledge gaps and future research directions for improving the efficacy of Trichoderma-based BCAs are discussed.