The European demand for stevia-derived products is steadily increasing and the possibility to grow stevia organically represents an aspect of pivotal importance in obtaining sustainable and safe products. Arbuscular Mycorrhizal Fungi (AMF) can be relevant for organic agriculture since they can act as natural fertilizers, with interesting effects on crop yield and secondary metabolites. Consequently, the aim of this study was to evaluate the effect of AMF symbiosis and phosphorus fertilization on the antioxidant properties of Stevia rebaudiana Bertoni leaves. Six treatments were compared in a pot trial established in Pisa (central Italy), testing three phosphorus (P) levels (0, 25 and 50 mg P2O5/kg of soil as triple superphosphate) in plants grown with and without AMF inoculation. Rhizoglomus intraradices has been used as inoculum. Sampling has been carried out before flowering, 123 days after transplanting. The antioxidant properties of aqueous leaf extracts were investigated, in terms of total phenols (Folin-Ciocalteu method), total flavonoids (aluminum-chloride method), and antioxidant activity, assessed both in vitro (ORAC assay) and at cellular level (CAA assay). The obtained results showed that AMF symbiosis and P level were able to affect the investigated parameters. In particular, AMF-treated plants were characterized by the lowest content of total phenols and flavonoids as well the lowest ORAC values. No significant differences (P > 0.05) were recorded for cellular antioxidant activity (7.94 μmol quercetin equivalents/g stevia dry leaves, as mean value). In addition, this research highlighted that the addition of 25 mg of P2O5 to the soil significantly increased the total phenolic and flavonoid content, together with the antioxidant activity (measured by ORAC assay). Conversely, the highest CAA values were recorded with 50 mg of P2O5. Definitively, this study provides useful information on stevia response to AMF symbiosis and phosphorus fertilization, highlighting that the antioxidant properties of stevia leaves can strongly vary as a function of AMF, P and AMFxP interaction.
Influence of arbuscular mycorrhizal fungi and phosphorus nutrition on secondary metabolite production and antioxidant activity of Stevia rebaudiana Bert.
Barbara Passera;Silvia Tavarini;Luciana G. Angelini;
2016-01-01
Abstract
The European demand for stevia-derived products is steadily increasing and the possibility to grow stevia organically represents an aspect of pivotal importance in obtaining sustainable and safe products. Arbuscular Mycorrhizal Fungi (AMF) can be relevant for organic agriculture since they can act as natural fertilizers, with interesting effects on crop yield and secondary metabolites. Consequently, the aim of this study was to evaluate the effect of AMF symbiosis and phosphorus fertilization on the antioxidant properties of Stevia rebaudiana Bertoni leaves. Six treatments were compared in a pot trial established in Pisa (central Italy), testing three phosphorus (P) levels (0, 25 and 50 mg P2O5/kg of soil as triple superphosphate) in plants grown with and without AMF inoculation. Rhizoglomus intraradices has been used as inoculum. Sampling has been carried out before flowering, 123 days after transplanting. The antioxidant properties of aqueous leaf extracts were investigated, in terms of total phenols (Folin-Ciocalteu method), total flavonoids (aluminum-chloride method), and antioxidant activity, assessed both in vitro (ORAC assay) and at cellular level (CAA assay). The obtained results showed that AMF symbiosis and P level were able to affect the investigated parameters. In particular, AMF-treated plants were characterized by the lowest content of total phenols and flavonoids as well the lowest ORAC values. No significant differences (P > 0.05) were recorded for cellular antioxidant activity (7.94 μmol quercetin equivalents/g stevia dry leaves, as mean value). In addition, this research highlighted that the addition of 25 mg of P2O5 to the soil significantly increased the total phenolic and flavonoid content, together with the antioxidant activity (measured by ORAC assay). Conversely, the highest CAA values were recorded with 50 mg of P2O5. Definitively, this study provides useful information on stevia response to AMF symbiosis and phosphorus fertilization, highlighting that the antioxidant properties of stevia leaves can strongly vary as a function of AMF, P and AMFxP interaction.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
