Trellis systems of mother vines impact the wood resident microbiome of two grapevine rootstocks cultivars

Grapevine nursery industry produces millions of benchgrafted vines starting from the growth of rootstock mother vines. With few exceptions, rootstocks shoots are usually sprawled on the ground, an inexpensive method that may favor infections by trunk disease pathogens, compromising the quality of the propagation material. More rarely, trellis systems are applied to rootstock mother vines to improve the functional leaf area and its exposure to the sunlight. Different trellis system therefore influences the canopy microclimate: this and the lack of contact with the soil occurring by trellising rootstock mother vines may positively shape the dynamics of the epiphytic and endophytic microbial communities. Through a DNA metabarcoding approach, this study investigated the impact of two trellising methods (a trellis system with a transpiring fabric applied to protect sprawled rootstocks from the soil) compared to the traditional sprawled rootstocks (two cultivars: Kober 5 BB and 110 Richter), on the resident fungal and bacterial communities, with a specific focus on wood pathogens. Beta diversity of the bacterial and fungal communities, including epiphytic and endophytic communities, resulted to be affected by the temporal distribution of the rootstock microbiome. Such diversity was more evident when comparing a trellised rootstock (cv. Kober 5 BB) with the same plant material sprawled on the ground. The results show that the sprawling shoots, compared to vertical-positioned shoots, are more exposed to soilborne microorganisms and pathogens as a consequence of the contact with the inoculum in the soil and the higher temperatures and humidity.