The effect of different concentrations of salicylic acid on some of morphological traits, gene expression of Ent-kaurenoic acid 13-hydroxylase and the amount of steviol glycosides in Stevia

Stevia rebaudiana is a sweet herb containing steviol glycosides (SGs), which is used as a natural sweetener. The study of gene expression patterns in response to elicitor treatments is important for biotechnological purposes. Nowadays, salicylic acid (SA) is an abiotic elicitor that has commonly been applied to elicit secondary metabolites accumulation in tissue culture of medicinal plants. Exclusive synthesis of steviol starting from terpenoied pathway of chloroplast and with production of kaurenoic acid 13-hydroxylase (KA13H) leads to the synthesis of glycosides such as stevioside and ribodioside A. In this study, the effect of different concentrations of salicylic acid (SA) was evaluated on some morphological traits, the amount of steviol glycosides (SGs) production and gene expression of KA13H. Accordingly, the morphological traits significantly changed by increasing the salicylic acid concentration. Based on the HPLC and gene expression data, the highest SG level and KA13H expression were observed at a concentration of 50 μM of SA. Moreover, rebaudioside A was higher at 75 μM of SA. It is notable that salicylic acid is more effective on the ratio of glycosides than the type of them. However, more investigations are needed to confirm the impact of the post-transcriptional, translational, and post-translational processes on SGs production.