Assessment of Stevioside Content, Shoot Proliferation, and Root Induction of Stevia rebaudiana Bertoni under In vitro Conditions

Background: Stevia rebaudiana Bertoni, an important anti-diabetic medicinal plant, becomes an inevitable alternative to sugar. Due to the propagation difficulties, tissue culture is the best alternative for rapid mass propagation of stevia plants. Objective: The present study was conducted to optimize a protocol for rapid micropropagation of Stevia rebaudiana by shoot tip explants and to investigate the effect of growth regulators concentration on steviol-glycosides content under in vitro culture conditions. Methods: Young nodal stem explants were collected from a young growing plant and the effects of media and growth regulators on shoot proliferation were studied. Shoots produced on optimal medium for shoot proliferation were used for rooting experiments and the effects of IBA, NAA, and active carbon on root induction in both full MS and half MS media were investigated. Results: Based on the results obtained from the proliferation stage, there was no significant difference between growth regulator levels. Analysis of data obtained from rooting experiment, revealed that there are significant differences between growth regulators in leaf length, shoot dry weight, and root fresh weight. Based on the results of mean comparison, plantlets grown on free active carbon media had the higher biomass than those grown on media supplemented with 2 mg.L-1 active carbon. The highest content of stevioside (8.18%) was observed at half MS medium supplemented with 0.2 mg. L-1 IBA, and 2 mg.L -1 active carbon. Conclusion: Plant growth regulators can be included among the factors affecting shoot proliferation and root induction of Stevia rebaudiana. Micropropagation of stevia can be improved by altering the macro elements concentration and adding activated carbon. In conclusion, half MS medium supplemented with 0.2 mg.L-1IBA, and 2 mg.L-1active carbon was superior for stevioside content.