Dual inoculation with AMF and associated bacteria improves nutraceutical value of sweet basil grown under commercial conditions

We investigated the ability of the arbuscular mycorrhizal symbiont Rhizophagus intraradices and its associated plant growth promoting bacteria (PGP) Sinorhizobium meliloti TSA41 and Streptomyces sp. W43N to improve the antioxidant activity, the production of health-promoting phytochemicals and plant growth regulators in two different cultivars of sweet basil (Ocimum basilicum) under commercial growth conditions: Tigullio, with green leaves and Dark Opal with purple leaves. Mycorrhizal and non-mycorrhizal plants with similar phenology and phosphorus (P) nutritional status were used in order to rule out P nutrition-dependent effects. Antioxidant activity and carotenoids content of Dark Opal leaf extracts were consistently higher than those of Tigullio. Dark Opal was more responsive than Tigullio to the dual inoculation treatment, showing higher antioxidant activity, anthocyanin and rosmarinic acid leaf levels. Present results suggest that dual inoculation with R. intraradices and PGP bacteria may represent an efficient strategy to improve the biosynthesis of secondary metabolites with health-promoting activities in basil plants.