Phenolics content and antioxidant activity in the leaves of two artichoke cultivars are differentially affected by six mycorrhizal symbionts

Globe artichoke is cultivated for its flower heads and as the source of pharmaceutical compounds from the leaves, whose extracts contain a high level of health-promoting compounds and show one of the highest antioxidant capacities reported for vegetables. The content and composition of such beneficial plant secondary metabolites may be greatly affected by cultivation variables, including plant genotype and mycorrhizal symbiosis. This study was carried out to gain knowledge on antioxidant activity, total phenols and chlorogenic acid levels in the leaves of two artichoke cultivars, Romanesco and Tema, as affected by six arbuscular mycorrhizal fungi (AMF) belonging to diverse genera, species and isolates. The six AMF showed significantly higher percentages of root colonization in Romanesco (46 %) than in Tema (32 %), and different colonization dynamics. The overall pooled data showed that in Romanesco the levels of total phenols increased by 35 %, chlorogenic acid by 67 % and antioxidant activity by 43 %, compared with Tema. The six AMF differentially affected such levels, with Claroideoglomus claroideum 22W3 as the only isolate producing significant increases compared with controls, for total phenols and chlorogenic acid, and with C. claroideum 22W3 and Funneliformis mosseae IMA1 as the isolates enhancing antioxidant activity, compared with controls. Moreover, a strong correlation was found between total phenols and antioxidant activity in the leaves of both artichoke cultivars. This work, comparing the highest number of diverse AMF studied so far in relation to their modulation of plant secondary metabolism, expanded our knowledge on their functional diversity and allowed the detection of the best performing symbionts to be utilized for obtaining artichoke leaves with enhanced health-promoting activities.