Testing the effects of commercial bioinoculants on grapevine growth and associated mycorrhizal fungal community

Commercial bioinoculants are considered as an alternative to reduce the dependence of grapevines on agrochemicals. However, their effects on native soil arbuscular mycorrhizal fungi (AMF) communities are still poorly understood. The aim of this study was to evaluate the influence of different bioinoculants on the community composition of native AMF communities of grapevine roots and to assess their performance and effects on grapevine plants. Two-year-old own-rooted Cabernet sauvignon vines were potted into a non-sterile orchard-collected soil with low mineral nutrient and neutral pH and inoculated with one of five commercial bioinoculants and placed in a greenhouse. Root colonization, leaf nitrogen concentration, plant biomass and root morphology were evaluated, and AMF communities of inoculated and non-inoculated grapevine roots were profiled using high-throughput sequencing of fungal 18S and ITS2 rDNA gene regions. Contrary to our predictions, no differences between native AMF communities and commercial AMF bioinoculants treatments were detected. Inoculation induced positive changes in root traits resulting in increased AMF colonization, plant biomass and leaf nitrogen but reduced carbon to nitrogen ratio. Most of these plant functional traits were positively correlated with the relative abundance of operational taxonomic units assigned to Glomus, Claroideoglomus and Rhizophagus genera. These results suggested synergistic interactions between commercial AMF bioinoculants and native AMF communities to promote grapevine growth.