Microbial antagonists and botanicals mediated disease management in tea, Camellia sinensis (L.) O. Kuntze: An overview

Tea, Camellia sinensis (L.) O. Kuntze (family Theaceae) known for high antioxidant value on account of polyphenolic compounds predominantly of catechins, have long history of cultivation and utilization. Tea plant rhizosphere harbors an array of microbial antagonists (MA) effective against many of the soil borne diseases. Green management of diseases using MA coupled with botanicals is relatively a new approach in tea plantation, considering chemical residue free tea as major trade requirement. A variety of MA have shown their worth in curbing soil borne as well as foliar/stem diseases, however very limited commercial bioformulations have found commercial field application, despite so much cutting edge research. On the contrary, botanicals are yet to carve a niche in suppressing pathogens, as evident from majority of in vitro studies, thereby, often questioning their utility under field condition. However, application of MA in consortium mode (using rhizosphere and endosphere microbial communities) is known to enhance intensity as well duration of defense signaling, thereby, elevating the transcriptional activation of several metabolic pathways and consequent suppression of pathogens associated with variety of tea diseases. Biochemical analysis of tea plants treated with either MA or botanical extracts under challenge inoculation of pathogens displayed an enhanced expression of peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase activities collectively contributing towards improved antioxidant profiling, a prerequisite to disease resistance response. The proposed review envisages the growing possibilities on use of MA and botanicals as greener side of disease management in tea crop.