Effect of salicylic acid and benzothiaodiazole on antioxidative enzymes and phenolic contents in Indian mustard (Brassica juncea) and rapeseed (B. napus)

A series of experiments were performed to evaluate the biochemical response of Indian mustard (Brassica juncea) and rapeseed (B. napus) to salicylic acid (SA) and benzothiadiazole (BTH). Four treatments of SA and BTH were given to 10 week old plants upto four consecutive weeks. Anti-oxidative enzyme activities and phenolic contents were evaluated after 72 hr of treatment. An increase in antioxidative enzyme activities and phenolic contents was observed in all the treatments after 1^st, 2^nd and 3^rd spray followed by a decrease after 4^th spray. After 3^rd spray, the treatment containing 3 ppm BTH + 33 ppm SA showed 1.6-, 1.7-and 1.2-fold increase in peroxidase (PO), phenylalanine ammonia lyase (PAL) and superoxide dismutase (SOD) activities in B. juncea, whereas the same treatment in B. napus plants caused 1.7-and 1.9- and 1.2-fold increase in PO, PAL and SOD activities, respectively, over control. Another treatment containing 7 ppm BTH + 17 ppm SA showed 1.9- and 1.7-fold increase in total phenol content in B. juncea and B. napus plants, respectively, than control after 3^rd spray. These elicitors when applied in combinations showed synergistic effect on the induction of antioxidative enzyme activities and phenolic contents as compared to their individual applications. Thus, combinations of elicitors can be used to effectively combat Alternaria blight disease in Brassica species.