Effect of phytohormones on the accumulation of steviol glycosides in Stevia rebaudiana

Abstract

Stevia rebaudiana Bert. (Bertoni) is economically important for its natural sweeteners, steviol glycosides (SGs), mainly stevioside (St) and rebaudioside A (RebA). Stevia seed germination is poor; therefore, plant regeneration in vitro could be a tool to obtain a homogenous plant population. Administration of different phytohormone enhances the production of plants with good agronomical traits and SGs content. The aim of this study was to determine the effect of phytohormones and its combination on the accumulation of St and RebA in callus, stems and leaves. Additionally, other biochemical traits such as amount of total phenolics, total flavonoids and antiradical scavenging activity were determined. In callus supplemented with KIN, TPZ or BAP, RebA concentration was the same (0,23-0,28 mg/g), however the concentration of St was the 2- and 4-fold higher with BAP and KIN than with TDZ (0,87 mg/ml). Stems formed in NAR and NAR+BAP supplemented media had very low concentration of SGs (0,04-0,32 mg/g) mainly due to decrease of St. In leaves, SGs concentration decreased from 0,87 mg/g to 0,40 mg/g with increase of NAR from 1 to 3 µmol. BAP (1 µmol) slightly increased SGs when combined with 2 or 3 µmol NAR but decreases with 1 µmol NAR. There is a strong correlation of SGs in leaves and stems with total amount of fenolics and flavonoids excluding an outlier of NAR (1 µmol). It can be concluded that micropropagation conditions are crucial for SGs accumulation, however, further investigations of the sustainability of SGs concentration differences during plant development are needed