The positive role of steviol glycosides in stevia (Stevia rebaudiana Bertoni) under drought stress condition

Steviol glycosides (SVglys) are a group of diterpenoids mainly present in the leaves of stevia (Stevia rebaudiana Bertoni). An experiment was conducted to find the functional role of SVglys compounds in stevia affected by drought stress. In this study, a liquid blend of SVglys (200 ppm) was sprayed on stevia plants grown in well-watered (90% field capacity) and drought-stress conditions (45% field capacity) and then the morphological traits and metabolites were evaluated. It was observed that leaf losses caused by drought stress were stopped through external application of SVglys and consequently the harvest index of stevia was increased. Metabolite analysis of stevia leaves showed that the total SVglys content was significantly decreased due to drought stress, but was compensated by external application of SVglys. Among the SVglys, Rebaudioside A responded more to external SVglys. A slight promotion in total antioxidant activity of stevia leaves was observed when external SVglys was applied. The glucose availability in stevia leaves was increased by external application of SVglys but only in well-watered plants. According to our findings, it can be concluded that in stevia, SVglys may have a positive function in drought stress tolerance by exerting a protective role under such conditions.