Accumulation of flavonoids and phenolic compounds in olive tree roots in response to mycorrhizal colonization: A possible mechanism for regulation of defense molecules

The arbuscular mycorrhizal (AM) fungus promotes plant growth and can alter the production of primary and secondary metabolites. The aim of this work was to determine the influence of AM fungi colonization on the content of phenolic compounds, flavonoids and soluble carbohydrates in olive (Olea europaea L.) tree roots. The results revealed that mycorrhizal plants had a higher content of flavonoids and total phenols. Analysis of sugar contents showed enhanced levels of sucrose and fructose in mycorrhizal roots, while glucose amounts stayed constant. The DPPH radical-scavenging activity of the mycorrhizal root methanolic extracts was higher than that of the non- mycorrhizal root methanolic extracts. These results indicated that olive tree roots contain significant amounts of phenolic compounds, important factors for antioxidant capacity, which can be substantially modified by colonization of olive trees with AM fungi.