Effect of Some Elicitors on Morphophysiological, Biochemical and Molecular Traits of Stevia

Abstract

Stevia rebaudiana Bert. is a medicinal plant used as a calorie-free sweetener due to the presence of steviol glycosides in its leaves. The present study evaluated morphological, biochemical, and molecular changes of stevia under salicylic acid (SA) elicitors (0, 25, 50, 75 and 100 µM) and yeast extract (YE) (0, 1, 2, 3 and 5 g/L) under in vitro conditions. The results showed significant effects of elicitors on morphological traits and photosynthetic pigments of stevia. The highest morphological traits were observed at 25 µM and control treatments of SA and YE respectively. On the other hand, increasing the concentrations of both elicitors resulted in lowered morphological traits. In general, plants treated with YE showed lowered growth, with the concentration rise lowering the growth further. HPLC results showed an increase in steviol glycosides content in 50 µM SA and 2 g/L YE treatments and then the highest amount of stevioside and rebaudioside A was at concentrations of 25 µM and 3 g/L. Investigation of expression levels of four genes (KA13H, UGT74G1, UGT76G1, and UGT85C2) indicated that the highest rate of expression occurred at the concentrations of 50 µM SA and 2 g/L of YE. While, control treatment had the lowest levels expression of the studied genes in both elicitors, which indicates the significant effect of elicitors compared to the control. These results demonstrate the significant effect of SA and YE at medium concentrations on levels of expression of key genes of biosynthetic pathway as well as the production of stevioside and rebaudioside A. Thus, this approach could be employed to elevate the steviol glycosides’ levels under in vitro conditions.