In-vitro Micropropagation and Evaluation of Antimicrobial Activity of Stevia rebaudiana

Abstract

Poor seed germination and variability among seed-derived plants constrain the propagation of Stevia rebaudiana. The present study investigated an in vitro strategy for rapid regeneration and analysed the antibacterial activity of Stevia rebaudiana, which belongs to the family Asteraceae. It is a well-known herb that has been extensively used in the treatment of diabetes. It is also used for high blood pressure and obesity. An in vitro micropropagation method was developed because poor seed germination is a major factor limiting the large-scale cultivation of this plant in vivo. Propagation by seed does not allow the production of a homogeneous plant population, resulting in considerable variability in important features such as sweetness levels and composition. A regeneration system for Stevia rebaudiana was established using explants (leaves and shoot tips) and MS medium with different hormone concentrations to produce callus and shoots, respectively. In vitro-grown callus and shoots of Stevia rebaudiana were cultured on nutrient MS medium. After 4 weeks of incubation, highly efficient callus induction was recorded on MS medium containing 3.0mg/l 2, 4-D. The highest number of shoots (50 per culture) and the greatest shoot length (60 mm) were recorded on MS medium supplemented with 2.0mg/l BAP and 2.0mg/l KN. MS medium containing 3.0mg/l KN produced 20 shoots per culture, with a shoot length of 50 mm. In vitro- and in vivo-grown leaf extracts prepared using different solvent systems were analysed for potential antibacterial activity against medically important Staphylococcus aureus strains using the agar-well diffusion method. The methanolic extracts of Stevia rebaudiana inhibited Staphylococcus aureus, whereas the petroleum ether extracts showed no inhibitory effect in the reported assay. The antibacterial activity of the methanolic extracts was compared with the reference antibiotic amoxycillin.