GIBBERELLIN APPLICATION INFLUENCES ON EX VITRO GROWTH, FLOWERING AND STEVIOL GLYCOSIDE ACCUMULATION OF STEVIA REBAUDIANA BERTONI

Stevia (Stevia rebaudiana Bertoni) is a small perennial herb with incredible sweetening property. Stevia is known to contain steviol glycosides (SGs), which are about 300 times sweeter than sucrose at their concentration of 4% (w/v). However, the growth of stevia plants and their SGs production are known to be influenced by external and internal factors. In this study, an ex-vitro experiment was conducted to determine the effect of exogenous GA3 application on the growth, flowering and steviol glycoside (stevioside and rebaudioside A) accumulation in stevia under Philippine condition. A previously established tissue culture-derived plant was used as mother plants and categorized into two groups: (1) non-flowering (NF) and (2) flowering (F). Stevia stem cuttings were sprayed with GA3 solutions of various concentrations: 0, 50, 100 and 200 mg L-1 at 1-week interval for 5 weeks. NF plants sprayed with GA3 showed significant difference in shoot length, number of shoot tips, length of longest primary branches compared to the control. NF plants produced more leaves than F at any GA level but without significant difference. Application of gibberellic acid (GA3) neither delayed nor inhibits flowering of ex vitro stevia plant but significantly reduced the flowering intensity of the plant. Exogenously applied GA3 also did not affect SG accumulation in the leaves and flowers.