An efficient callus initiation and direct regeneration of Stevia rebaudiana
The experiment was carried out to establish an efficient callus induction system of Stevia rebaudiana from a variety of explants as well as direct regeneration from nodes. Callus initiation was done to extract secondary metabolites. However direct regeneration is essential for rapid large-scale clonal propagation. Among leaf, node and inter-nodal explants, the best callus initiation performance was observed by nodes. MS medium fortified with α-naphthalene acetic acid (NAA) 2.0 mg/L + 6-benzyladenine (BA) 2.0 mg/L showed the highest (93.33 ± 6.67%) callus induction by nodal explants. Though inter-nodal explants showed a moderate response (73.33 ± 6.67%) for callus induction in MS medium complemented with NAA 3.0 mg/L + BA 1.0 mg/L, nodal explants showed higher response (86.67 ± 13.33%) than inter-nodal explants in that nutritional environment. Leaf explants always showed very poor callus. However, the best direct regenerating medium was MS medium + BA 1.0 mg/L for multiple shoot proliferation and then transferring those shoots to ½ MS medium + NAA 1.0 mg/L for root formation.
Key words: In vitro, Stevia rebaudiana, 2,4-D, α-naphthalene acetic acid (NAA), 6-benzyladenine (BA), plant growth regulators.