Effects of Explant Type and Plant Growth Regulator Combinations on In Vitro Direct and Indirect Regeneration of Stevia rebaudiana

Stevia rebaudiana is a medicinal plant belonging to Asteraceae family. This experiment was carried out to optimize the in vitro callus induction and plant regeneration of Stevia rebaudiana. The explants used in this study were leaf, shoot tip, nodal segments with two leaves and nodal segment without leaves derived from in vitro grown plantlets. The explants were transferred to PGR-free MS medium or supplemented with BA (0.1, 0.5 and 2mgl-1) solely or in combination with 0.5mgl-1 IBA and TDZ (0.1, 0.5 and 2mgl-1) solely or in combination with 0.5mgl-1 IBA. The highest callus percentage and callus volume induced with culturing leaf explant on MS medium containing 0.1 mgl-1 TDZ. The nodal segment without leaves cultured on MS medium containing 2mgl-1 BA + 0.5mgl-1 IBA produced the highest regenerated shoot number. The highest and lowest shoot length was observed in shoot tip cultured on MS medium containing 0.1mgl-1 BA + 0.5mgl-1 IBA and MS medium containing 2mgl-1 BA + 0.5mgl-1 IBA, respectively. Indirect shoot regeneration was observed only in leaf explant cultured on MS medium containing 0.5mgl-1 TDZ + 0.5mgl-1 IBA. The highest percentage of root induction was observed with culturing shoots on MS medium containing 0.1mgl-1 IBA.