Phenylalanine ammonia-lyase gene induction with benzothiadiazole elevates defence against Lasiodiplodia theobromae in tea in India

Tea is widely used as an aromatic beverage cultivated in more than 35 countries from different continents. The global production of tea during the year 2015–2016 was 5,303 million kg where India stands 2nd contributing 23% of the world production. Diplodia disease is one of the most common diseases of tea in sub-Himalayan West Bengal, India. Phenylpropanoids act as a precursor of several secondary metabolites that are synthesized at the time of biotic and abiotic stress conditions. During the induction of systemic acquired resistance, salicylic acid production is regulated by phenylalanine ammonia-lyase (PAL) gene expression. In this communication, twelve-month-old tea seedlings (TV-26) were treated with benzothiadiazole (BTH) and inoculated with Lasiodiplodia theobromae. Transcript accumulation in different treatments, that is treated-uninoculated, untreated-inoculated and treated-inoculated were measured in comparison with untreated-uninoculated control to study the effect of BTH in defence induction. From the results, it was evident that BTH-treated and L. theobromae-inoculated plants showed higher transcript accumulation (3.81 μg/μl) and reduced disease index (3.8 ± 0.02) in comparison with untreated control where transcript accumulation was 3.26 μg/μl and disease index reduced to 14.6 ± 0.05. After sequencing, nucleotide and deduced protein sequences were compared, and 3D structure was established where three lyase superfamily (cl26059) motifs were found. The increase in PAL activity was also observed in treated-inoculated plants (from 2.5 to 4.4 μmol min−1 g−1) in comparison with healthy control (from 2.5 to 2.7 μmol min−1 g−1) after 4th day of treatment. Nonetheless, BTH might be one of the significant inducers of PAL which can be used to induce of disease resistance in tea plants in India.