Commercial Bioinoculants Increase Root Length Colonization and Improve Petiole Nutrient Concentration of Field-grown Grapevines

Agricultural bioinoculants containing arbuscular mycorrhizal fungi represent a potential opportunity to reduce the dependence of grapevines (Vitis) on agrochemicals. This field study assessed the ability of four commercial bioinoculants to colonize grapevine roots and their effects on petiole nutrient concentration, berry composition, and root morphology of ‘Pinot noir’ (Vitis vinifera) grafted onto rootstock ‘Couderc 3309’ (Vitis riparia × Vitis rupestris) and ‘Riesling’ (V. vinifera) grafted onto ‘Couderc 3309’ and Selection Oppenheim four (Vitis berlandieri × V. riparia). Three bioinoculants increased root mycorrhizal colonization; however, regardless of the treatment, mycorrhizal fungal structures were enhanced. Grapevine petiole nutrient concentration was improved by bioinoculants. Root diameter, root length density, and specific root length increased with greater mycorrhizal root colonization. Using bioinoculants to reduce chemical fertilizers may be a good strategy to improve grapevine productivity and health in cool climates; however, the impact of mycorrhizal bioinoculants in the vineyard may differ among scion–rootstocks, edaphoclimatic conditions, and vineyard soil microbiomes.