Effects of grapevine mycorrhizal association on fine root dynamics depend on rootstock genotype

Abstract

Context and Purpose of the study. Arbuscular mycorrhizal fungi (AMF) symbiosis with grapevines is a key component of vineyard ecosystems. AMF enhance nutrient uptake, water absorption, and resilience to environmental stresses, while also improving soil structure and influencing root system development. However, a better understanding of the impact of AMF on grapevine belowground traits is still needed. This study aimed to investigate the growth response of grapevine fine roots and root morphology to AMF inoculation across key phenological stages over two growing seasons.

Material and Methods. The study was conducted at Cornell vineyards in Lansing, New York in 2021 and 2022. The experiment followed a 2×2 split plot design with five replications (100 vines in total). Two-year old Pinot noir grapevines grafted onto 3309C and 101-14 Mgt rootstocks were the main plots, with sub-plots of vines either inoculated or not with a bioinoculant containing four AMF species. Fine root production and dynamics were monitored at budbreak, veraison and post-harvest using minirhizotron methods. Root morphology, AMF colonization, leaf area and leaf blade nutrient concentration were also evaluated.

Results. Inoculation significantly increased root length colonization (RLC) compared to control plants. Interestingly, the degree of colonization varied between rootstock genotypes, with RLC increasing by 11% and 8.71% in 3309C compared to 101-14 Mgt for inoculated vs. control plants at veraison in 2021 and 2022, respectively. While both inoculated rootstocks showed greater fine root production vs. control plants, overall fine root growth (<1 mm in diameter) was 57% higher in inoculated 3309C than in inoculated 101-14 Mgt over the two growing seasons. Leaf area, root diameter and root length were greater in inoculated vines than in control plants, particularly for 3309C. Significant differences in petiole nutrient concentration were observed between treatments, but only in the first growing season for both root systems. Our results highlight the importance of minirhizotron technology in advancing our understanding of the spatial and temporal development of the grapevine root systems and the effects of AMF association in the field. Gaining insights into the influence of AMF on grapevine root systems and scion genotypes as well as their contribution to vine growth, could lead to new strategies for adapting viticulture to climate change and reducing dependence on agrochemical input.