Trichoderma reesei as an elicitor triggers defense responses in tea plant and delays gray blight symptoms.

Gray blight caused by Pestalotiopsis-like species is a major disease of tea crop worldwide including India, causes significant losses in tea production. Management of disease using fungal biocontrol agents is considered an alternative eco-friendly approach to synthetic fungicides. The present study explores the efficacy of Trichoderma reesei in the gray blight management in tea crop and activation of defense related enzymes against gray blight pathogen by developing a tri-trophic interaction system. Out of 16 isolates of Trichoderma species screened in laboratory against Pseudopestalotiopsis theae, a gray blight pathogen, isolate TRPATH01 had highest antagonistic activity (81.2%) against Ps. theae and was found to produce inhibitory volatile and non-volatile metabolites. Based on ITS and TEF-1 alpha sequencing, the isolate TRPATH01 was recognised as T. reesei. The methanolic extract of T. reesei was also found effective against Ps. theae at 200 µg/mL also confirmed presence of highest volatile compounds. The isolate also produced hydrolytic enzymes such as chitinase, cellulase, protease, and lipase. Under nursery conditions, 2% and 5% concentrations with 2 × 106 conidia/ml of T. reesei were able to reduce 67.5% to 75.0% of disease severity over pathogen inoculated controls. Moreover, compared with positive and negative controls, T. reesei -treated tea plants showed increased shoot height, stem diameter, shoot and root fresh weight at 45 days after inoculation. Principal component analysis capturing 97.1% phenotypic variations, which revealed that the tea plants co-inoculated with Ps. theae and T. reesei exhibited significantly upregulated accumulation of defensive enzymes viz., polyphenol oxidase, peroxidase, phenylalanine ammonia lyase, phenolics, ß-1, 3-glucanase, and chitinase when compared to both controls. Hence, T. reesei could provide an eco-friendly and viable mitigation option for gray blight in tea gardens by inducing defense-related enzymes.

How the Global Tea Industry Copes With Fungal Diseases - Challenges and Opportunities.

Tea (Camellia sinensis [L.] O. Kuntze) is a plantation crop, grown commercially in Asia, Africa, and South America. Among biotic threats to tea production, diseases caused by fungal pathogens are most significant. Worldwide, tea plants are challenged by several root, stem, and foliar diseases. Foliar diseases, blister blight, gray blight, and brown blight are particularly important as they adversely affect the bud and the two youngest leaves, causing loss of harvestable shoots. Over the past several decades, climate change and field management practices have influenced the risk of crop damage by several fungal pathogens, as well as the development and spread of diseases. Management interventions, such as the adoption of good cultural/agronomic practices, use of fungicides and microbial biocontrol agents, plant defense elicitors, and deployment of resistant cultivars, have mitigated damage to tea plants caused by fungal diseases. A clearer understanding of knowledge gaps and the benefits of plant disease management strategies available is needed. The present article reviews the prevailing knowledge of major fungal pathogens of the tea crop, their genetic variability, the damage they cause and its economic impact, and the need for new disease management strategies as climate change intensifies. We will also emphasize important knowledge gaps that are priority targets for future research.