Clonal propagation and antimicrobial activity of an endemic medicinal plant Stevia rebaudiana

A procedure has been outlined for plant regeneration and antimicrobial screening of a medicinal herb, Stevia rebaudiana Bertoni, through in vitro culture of nodal segments with axillary buds.  Murashige and Skoog (MS) medium supplemented with 2.0 mg/L N6-benzyl amino purine and 1.13 mg/L indole-3-acetic acid in combination were found to be most effective in inducing bud break and growth, and in initiating multiple shoot proliferation at the rate of 39 microshoots per nodal explant after 30 d of culture. By repeated subculturing a high-frequency multiplication rate was established for production of elite lines of S. rebaudiana.Elongated shoots were transferred to rooting medium. MS medium supplemented with 2.0 mg/L indole-3-butyric acid was found to be best for rooting. In vitro and in vivo grown leaf extracts in different solvent system were screened for potential antimicrobial activity against medically important bacterial and fungal strains by agar well diffusion method. The chloroform and methanol extract exhibited a concentration dependent antibacterial and antifungal inhibition. Both in vitro and in vivo dried leaf extract showed similar antimicrobial activity. Therefore, commercial manufacture of active constituents from these improved elite lines would be useful and profitable.   Key words: Regeneration, antimicrobial, Stevia rebaudiana, medicinal plant