Efficient In Vitro Culture Protocol for Mass Propagation of Stevia (Stevia rebaudiana Bertoni) in the Philippines

Studies were conducted to develop an efficient in vitro culture protocol for mass propagation of stevia (Stevie rebaudiana Bertoni) using nodal explants and Murashige and Skoog's (MS) medium formulation supplemented with different types and concentrations of plant growth regulators. The two-step sterilization procedure, which involved the soaking of explants in 1.0% (v/v) sodium hypochlorite for 10 min followed by re-sterilization of contaminated cultures in 0.01% (w/v) mercuric chloride for 1 min, proved to be effective in producing the initial sterile explants of stevia. The MS medium supplemented with 1.0 mg L-1 6-benzylaminopurine (BAP) and 0.1 mg L-1 indoleacetic acid (IAA) was found optimum for callus formation. Greatest shoot proliferation was observed in medium with 5 mg L-1 BAP + 0.1 mg L-1 IAA, with 10 shoots produced per inoculum after 4 wk of culture. Increased elongation of shoots was attained when the microshoots were incubated in hormone-less MS medium before rooting. Regenerated shoots were successfully rooted on half-strength MS medium supplemented with 1.0 mg L-1 naphthaleneacetic acid.