Detrimental effects of copper and EDTA co-application on grapevine root growth and nutrient balance

Abstract Continuous application of Cu-based fungicides and molluscicides may lead to Cu accumulation in vineyard soils. Grapevine (Vitis vinifera L.) inoculation with arbuscular mycorrhizal fungi (AMF) can be a suitable strategy to increase plant tolerance to the excessive levels of this element in the soil. However, the simultaneous use of EDTA-based fertilizers or phytosanitary products in those vineyards can affect metal mobility in the soil, with potential negative consequences for plants. Therefore, this study aimed to elucidate the effect of AMF inoculation on grapevine performance in Cu contaminated soils, in the presence or absence of EDTA chelates. Two-year-old plants growing in pots filled with an Arenosol, previously inoculated or not with two different AMF, were subjected to three soil treatments: control, Cu addition; Cu and FeNaEDTA addition. Four months later, at the end of the growing season, plant vegetative growth parameters, root colonization as well as soil, root and leaf nutrient contents were analyzed. In the soil where Cu was applied, Rhizoglomus irregulare- and Funneliformis mosseae-inoculated plants showed significantly higher root biomass than the non-inoculated ones, and R. irregulare-inoculated plants were the ones with the highest root P and Fe concentrations. However, when Cu and FeNaEDTA were applied together to the soil, AMF inoculation was no longer an asset for grapevines, and overall, root biomass decreased, translocation of Cu to leaves was stimulated, and a significant decrease in leaf Mn concentrations was detected, below the levels found in control soils. For this reason, in soils with high Cu-concentrations, although mycorrhizal inoculation can be a suitable strategy to improve plant growth and nutrition, the use of EDTA-based products should be avoided, as it can lead to an amplification of the toxic effects commonly caused by the excess of Cu in plants.