Effect of Cadmium and Copper on Morphological and Physiological Parameters of Stevia rebaudiana Bert. Under in Vitro Conditions

Abstract

Background: Stevia rebaudiana Bertoni is a popular non-caloric sweetener being used all over the world for its anti-diabetic properties. Stevia contains phytochemical compounds known as diterpene glycosides that helps to reduce blood sugar, cholesterol, and blood pressure.  In vitro raised cultures are considered as an efficient way to produce essential secondary metabolites, especially through elicitation. This study aims to optimize culture conditions for the large-scale production of these economically significant metabolites using abiotic elicitors.Methods: Apical shoot, nodes as well as leaf explants from Stevia mother plants were used for micropropagation and callogenesis respectively. Murashige and Skoog (MS) medium supplemented with different cytokinins and auxins alone or in combinations were tried for obtaining the maximum yield of calli and plantlets. The calli and plantlets were subjected to different concentrations of copper sulphate and cadmium chloride. After 40 days of treatment, the data was recorded for morphological characters of elicitor-treated plants and calli. Chlorophyll content and antioxidant activity using DPPH assay were performed using treated leaves and calli extracts.Results: Among all the cytokinins tried for micropropagation, BAP at 0.5 mg/L in MS medium proved to be the best with 100% response by inducing 34 and 40 shoots/culture within 12 days of inoculation from shoot tip and nodal explants, respectively. For rooting, MS medium containing 0.6 mg/L of IBA was best producing 15-17 roots/culture within 10 days. Green friable and embryogenic calli was obtained in MS medium containing 1.0 mg/L TDZ with 0.1 mg/L NAA from leaf explants. A significant increase was observed in the elicitors-treated calli and plantlets biomass, chlorophyll content as well as antioxidant potential as compared to the control.Conclusion: The results of this study indicate that the cytokinins and auxins at lower concentrations gave significant results for micropropagation and callogenesis. Further, elicitation with copper sulphate and cadmium chloride has improved the biomass and antioxidant activity of calli and plantlets.Keywords: Stevia; Micropropagation; Callus induction; Elicitation; Antioxidant activity; Biomass    

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