Abstract
•Microbial antagonists showed higher inhibition of tea pathogen than botanicals.•Antagonists elicited tea defense via secondary metabolites against tea pathogen.•Higher leaf nutrients was observed with microbial antagonists than botanicals.•Antagonists registered higher yield of green tea leaves than botanicals.
Microbial bioagents and botanicals contrastingly different in modes of action, and despite being used over the years, their comparative efficacy are not yet fully explored with regard to management of grey blight disease caused by Pseudopestalotiopsis curvatispora Petch in tea plantation of Assam, India. Four microbial antagonists-based formulations and seven botanicals at 2.5–10% concentration were tesed against mycelial growth of grey blight pathogen through dual culture assay and poisoned food technique, respectively, under in vitro conditions. Resultantly, two botanicals viz., Pongamia pinnata L. and Xanthium strumarium L. and two microbial bioformulations viz., Biometa as Metarhizium anisopliae and Biogreen as Trichoderma viride -based consortium of microbial antagonists were evaluated, singly and in combination through field studies in a grey blight affected 12-year -old tea plantation (grey blight susceptible clone TV-23) established on acidic Inceptisol with regard to suppression in grey blight disease incidence (PDI), green tea yield, culturable soil microbial population, leaf nutrients composition, and biochemical properties of tea. The consortium of microbial antagonists (Biogreen + Biometa) registered 11.34% higher suppression in grey blight disease at 4% concentration over combination of P. pinnata + X. strumarium at 10% concentration, both sprayed 5 times at 30 days interval in 150- days period, besides single microbial antagonist (Biometa) being inferior to consortium of microbial antagonists (Biogreen). Such a reduction in PDI resulted in 22.9% higher yield of green tea leaves with consortium of bioagents over botanicals due to significant elevation in soil culturable microbial population, and leaf nutrient composition. These responses were eventually associated with an improvement in biochemical properties (Polyphenols, caffeines, and antioxidants acivity) of tea. Our study, hence, provided both, in vitro and field evidence in favor of multipronged benfits of consortium of microbial antagonists for an extended control of grey blight disease of tea, a reliable alternative to conventionally used chemical fungicides towards tea health care with enhanced quality parameters.