Biphasic dose–response and steviol glycoside production in Stevia rebaudiana B. under greenhouse conditions applying salicylic acid

Stevia (Stevia rebaudiana B.) is widely consumed for its medicinal properties and sweetening power. According to a hormesis curve, low doses of a stress factor can promote biostimulatory effects in plants. This research analyses the hormetic response of stevia plants (N = 90) to salicylic acid (SA) applied under greenhouse conditions. The methodology involved the evaluation of morphological variables, quantifying steviol glycosides (SGs) via HPLC, and analysing expression of key biosynthetic genes using qRTPCR. The results confirmed a dose–response effect of SA (0.1–0.5 mM), which optimised plant growth and modified gene expression, upregulating or downregulating signalling cascades, ultimately leading to higher accumulation of rebaudioside A, B, C, and dulcoside A. In contrast, higher concentrations (>3 mM) acted as distressors, inducing phytotoxicity and plant mortality. Specifically, 10 mM caused up to 100% mortality and severe leaf damage. This study concludes that controlled elicitation with SA is an effective biotechnological strategy to enhance the commercial quality, gene expression, and environmental stress tolerance of stevia crops.