An efficient regeneration system and steviol glycoside analysis of Stevia rebaudiana Bertoni, a source of natural high-intensity sweetener

Stevia is a natural, zero-calorie, intensively sweet extracted from the leaves of Stevia rebaudiana. Its sweet taste derives from a group of compounds known as steviol glycosides. In this study, an efficient micropropagation protocol for S. rebaudiana was developed for possible commercial implementation using Murashige and Skoog (MS) basal medium without plant growth regulators for most of the process. Direct shoot formation was achieved after cultivation of nodal segments on MS medium with or without plant growth regulators (benzyl amino purine [BAP], kinetin [KIN]) at various concentrations (0.1, 0.5, 1.0, or 2.0 mg L-1). Although all treatments produced two shoots per explants after 3 wk of culture, high concentrations of KIN and BAP (1.0 or 2.0 mg L-1) induced more callus formation. Rooting was achieved on MS medium containing 0.25 mg L-1 indole-3-acetic acid (IAA), which produced 8.1 roots per shoot after 3 wk of cultivation. After acclimatization of the regenerants in a portable greenhouse for 3 wk, all regenerants and seed-derived seedlings were transferred to field conditions for 16 wk. Steviol glycoside contents (% leaf dry weight) did not differ between leaves collected from regenerants and seed-derived plants. Rebaudioside A content ranged from 4.7 to 5.0% (w/w), while stevioside ranged from 6.4 to 6.9% (w/w). There was no significant difference between the two sampling periods (late vegetative and flowering stages) for the plants grown in the field. In this study, a cost-effective in vitro regeneration protocol was established that enables efficient, large-scale in vitro production of S. rebaudiana for field cultivation.