Abiotic Elicitor-Mediated Improvement of Innate Immunity in Camellia sinensis

Elicitor-induced natural defense machinery of plants could be proposed as an alternative, non-conventional, and ecologically-friendly approach for plant protection. In this work, the abiotic elicitor, calcium chloride (CaCl2), was used for inducing resistance in tea plants against blister blight disease caused by Exobasidium vexans. Foliar application of elicitor resulted in around 80 % disease inhibition over the control set, during the peak time of blister blight incidence at the experimental garden of Darjeeling Tea Research and Development Centre. A significant increase in the activities of defense enzymes like phenylalanine ammonia lyase (PAL), peroxidase, polyphenol oxidase, and beta-1,3-glucanase along with higher accumulation of total phenolics was observed. Treated plants also had elevated transcript levels of thaumatin, catalase, PAL, cinnamate 4-hydroxylase, and flavonoid 3'-hydroxylase genes compared to control plants. Further, the treatment-induced nitric oxide (NO) production was confirmed by real-time visualization of the NO burst using a fluorescent probe and spectrophotometric analysis. The result suggested that CaCl2 induced an array of plant defense responses making this compound a potential phytosanitary product with a challenging issue and a rather attractive option for sustainable organic tea cultivation practice.