European Grapevine Cultivars and Rootstocks Show Differential Resistance to Xylella fastidiosa Subsp. fastidiosa

Several Xylella fastidiosa subsp. fastidiosa (ST1) strains that cause Pierce’s disease were isolated from grapevine in Spain. In this study, we applied an approach to assess PD susceptibility among 24 different well-known Vitis vinifera subsp. vinifera cultivars and five rootstocks belonging to different species of the genus Vitis. Both were commonly commercialized, representing about 75% of the cultivated area in Spain. This method incorporated disease severity, disease progression, and water potential from the stem xylem. The trials were carried out under field and greenhouse conditions. The virulence of the Xff strain XYL 2055/17 was significantly higher than that of strain XYL 2177/18. However, while this difference in strain virulence did not seem to modify the susceptibility profiles of the cultivars, disease severity could be climate dependent. This work established two significantly different groups of European cultivars of grapevine characterized by high and low susceptibility to Xff ST1: cultivars with high susceptibility, including reference cultivars such as Tempranillo and Tempranillo Blanco, and cultivars with high resistance, such as Hondarrabi Zuri and Cabernet Sauvignon. Cultivar susceptibility was independent of the rootstock on which they were grafted. No conclusive data were found regarding the potential of water loss as an early detection test prior to symptom onset. This study provides a framework with which to advance cultivar susceptibility studies under different environmental conditions.