EFFECT OF GROWTH REGULATORS ON MICROPROPAGATION OF STEVIA (Stevia rebaudiana Bert.)

Abstract

This study was concerned with the micropropagation of stevia by tissue culture, in order to establish an efficient and reproducible in vitro propagation technique. The explants, shoot tip, leaf base with petiole and nodal segment of stevia were cultured on MS medium supplemented with 5 different concentrations (0.0, 1.0,2.0,3.0,4.0 and 5.0 mg/L) of BAP for shoot proliferation and elongation of stevia. Nodal segment performed best and BAP 3.0 mg/L was found optimum for shoot proliferation and elongation. The experiment with various cytokinin showed that BAP applied alone was the most effective cytokinin for stevia When BAP was used in combination with 2ip and KN, the number of shoot and their length were decreased, whereas the highest number of shoot (8.0) and length (7.8 cm) was found with the application of BAP 3.0 mg/L. The best response towards root induction was achieved on Yi MS medium supplemented with 1.5 mg/L NAA. Callus induction was observed, the best on MS medium containing 3.0 mg/L of 2, 4-D. Callus (0.3g) explanted on MS basal medium supplemented with different concentration and combination of NAA and BAP (Ti-control, T2-l.O mg/L BAP + 0.5 mg/L NAA, T3- l.O mg/L BAP + 1.0 mg/L NAA, T4- 1.0 mg/L BAP + 2.0 mg/L NAA, Ts-2.0 mg/L BAP + 1.0 mg/L NAA, T6-2.0 mg/L BAP + 2.0 mg/L NAA) to observe their effect on the subsequent growth and development of initiated stevia plantlets at 30, 60 and 90 days after inoculation (DAJ). However, T2 (1.0 mg/L of BAP + 0.5 mg/L ofNAA) gave the best result (8.9 shoots/ explant) in respect of the highest shoot proliferation and the highest number of root formation was 9 roots /shoot under T3 (1.0 mg/L BAP + 1 mg/L NAA) treatment at 90 days after inoculation (DAI). The regenerated plantlets were successfully established into the pots after proper hardening. The cocodust medium was found the best substrate for ex vitro establishment of stevia.