Effects of Culture System and Substrate Composition on Micropropagated Plantlets of Two Varieties of Stevia rebaudiana Bert.

Secondary metabolites in stevia leaves offer important therapeutic benefits. The germination problems of stevia seeds and the high heterogeneity of the resulting populations make micropropagation the preferred tool for obtaining a large number of plants in a short time. Until now, studies have focused on optimizing the action of growth regulators for the improvement of stevia micropropagated plantlets. In this project, we study alternative mineral nutrients in the substrate and two culture systems on micropropagated stevia plantlets to obtain proper amounts of enhanced plantlets. Methods: Criolla and Morita varieties; MS, MSM, and G substrates, and temporary immersion (TIS) and agar-medium systems were used. Biometric variables and damage to the cell membrane of the resulting plantlets were tested. Results: More productivity in the Criolla plantlets growing in MS solid medium and TIS. The Morita plantlets presented higher productivity in the solid MS, MSM, and G substrates and TIS. The explants growing in MS and MSM presented the highest productivity. The solid substrate was generally better than TIS. No damage to the cell membrane was found. Conclusions: The micropropagation efficiency of stevia plantlets of the two varieties has been enhanced without negative effects on their physiological condition. Consequently, any of the culture systems used, including bioreactors, can be of industrial application on a large scale.