ROLE OF SALICYLIC ACID IN STIMULATION OF PLANT DEFENSE SYSTEM AND INTERRELATED STEVIOSIDE PRODUCTION IN THE CALLUS OF Stevia rebaudiana Bertoni (ANGIOSPERMS; ASTERACEAE)

The present study investigates the role of salicylic acid (SA) in the stimulation of the enzymatic and non enzymatic defense responses and stevioside production of Stevia rebaudiana callus. For this the leaf generated callus on BAP (3.0 mg L-1) and NAA (4.0 mg L-1) in MS medium were subjected to different concentrations of salicylic acid (control, 50 µM, 100 µM, 150 µM, 200 µM and 250 µM). At 150 µM L-1 salicylic acid concentration, maximum stevioside production was recorded; at this level, an enhanced stevioside amount, up to 183 mg G-1 was reported through leaf generated callus. Salicylic acid at 250 μM L-1 in culture medium elicited the highest defense response. The ratio of chlorophylls a and bshow an increase at the lower concentration of salicylic acid, while at a the higher amounts (200µM L-1 and 250µM L-1), it started to decrease. At this level ascorbate peroxidase (APX), catalase (CAT), lipid peroxidase (LP), proline and hydrogen peroxide have showed elevated production, but superoxide dismutase (SOD) showed rather lower production. The study showed that perceptive SA application on callus of S. rebaudiana will be useful for enhanced production of the commercially valuable stevioside with the aid of elicited defense response.