Polyvinylpyrrolidone coated silver nanoparticles enhance in vitro growth and steviol glycoside production in Stevia rebaudiana

The plant Stevia rebaudiana, a natural source of high-potency, low-calorie sweetener, holds significant commercial and medicinal value. The present study investigates the potential of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) to modulate growth, secondary metabolite production, and genetic stability in S. rebaudiana under in vitro conditions. PVP-AgNPs (≤ 100 nm, 99.5% purity) were supplemented into Murashige and Skoog (¼ MS) media at concentrations ranging from 12.5 to 200 mg/L. Their effects on shoot elongation, node and leaf number, and accumulation of steviol glycosides (SG), i.e., stevioside and rebaudioside A (reb A), were assessed after 15 days of culture. The results revealed a concentration-dependent biphasic response. Among the tested treatments, most favorable growth was observed at 25 mg/L PVP-AgNPs, with significant increases in shoot length, leaf number, and node formation compared to the control. HPLC analysis showed that this concentration correlated with the highest stevioside and reb A accumulation, yielding approximately 1.36 folds higher concentrations than the control. Higher concentrations (≥ 100 mg/L) negatively impacted both growth and metabolite levels, suggesting potential inhibitory effects at elevated doses. Initial genetic fidelity screening using a selected RAPD and ISSR marker demonstrated consistent, monomorphic banding patterns among all nanoparticle-treated regenerants and the mother plant, suggesting an absence of detectable genetic variation within the targeted genomic regions. These findings indicate that PVP-AgNPs show potential to act as nano-elicitors to enhance biomass and glycoside yield in S. rebaudiana without inducing widespread genetic instability. This study highlights the potential application of AgNPs in improving tissue culture protocols for commercially important medicinal plants, offering a promising strategy for high-quality clonal propagation and metabolite optimization.