Different mycorrhizal symbionts affect phenolics content and antioxidant activity in diverse artichoke and tomato plant cultivars

Introduction Globe artichoke and tomato are considered “functional foods”, showing high levels of secondary metabolites with health-promoting activities. The content and composition of such bioactive molecules may be greatly affected by plant genotype and by the association with beneficial symbionts, such as arbuscular mycorrhizal fungi (AMF), a key group of soil microorganisms considered natural biofertilizers and bioenhancers. However, while plants have been widely investigated for bioactive molecules production, only few AMF were studied, thus limiting the full exploitation of their physiological and genetic diversity. Material and methods In this work the antioxidant activity and total phenolics of artichoke leaves and flower heads and of tomato fruits were assessed in different plant cultivars (two in artichoke and four in tomato) inoculated with AMF isolates belonging to diverse genera and species (Funneliformis mosseae, Funneliformis coronatus, Funneliformis caledonius, Rhizoglomus irregulare, Claroideoglomus claroideum, Glomus sp.). Results The different AMF isolates showed a variable rate of mycorrhizal colonization, depending on plant cultivar both in artichoke and in tomato. Differences in bioactive molecules were also observed among plant cultivars and symbionts. For example, significant increases of total phenolics and antioxidant activity, compared with controls, were observed in relation to the diverse AMF species used, with C. claroideum 22W3 as the best performing isolate. Moreover, in artichoke the levels of total phenols, chlorogenic acid and antioxidant activity increased in one cultivar, compared with the other. Conclusions The present study, comparing a high number of diverse AMF in relation to the production of health-promoting secondary metabolites, is important to enhance our knowledge on the functional diversity of this key group of soil beneficial microbes and to detect the best performing ones to be used for obtaining high quality food, which is an important societal issue strongly demanded by both consumers and producers.