Trellis systems of rootstock mother grapevines affect the wood microbiome

Management of rootstock mother vines is the first stage for bench-grafted grapevine production in nurseries. In source mother blocks, rootstock shoots are usually sprawled on the ground, which may favour infections by trunk disease pathogens, and compromise the quality of resulting propagation material. Trellis systems could be applied to rootstock mother vines to improve the functional leaf area and exposure to sunlight. Different trellis systems influence canopy microclimates, and the lack of contact with soil from trellising rootstock mother vines may affect epiphytic and endophytic microbial communities of resulting propagation material. DNA metabarcoding was used to investigate effects of two trellising methods (vertical trellis or transpiring fabric for protecting sprawled rootstocks from the soil), compared to traditional sprawled rootstocks, assessing on resident fungal and bacterial communities focussing on wood pathogens. The rootstock cultivars Kober 5 BB and 110 Richter were assessed. Bacteria and fungi betadiversities, including epiphytic and endophytic communities, were affected by the temporal distribution of the rootstock. Diversity was greater when comparing a trellised rootstock ('Kober 5 BB') with the same plant material sprawled on the ground. These results demonstrated that sprawling shoots, compared to vertically-positioned shoots, were more exposed to soilborne microorganisms and pathogens, due to contact with soil inoculum, and probably due to the increased temperatures and humidity in sprawling shoots.