Evaluation of Pierce’s Disease-Resistant Grapevine Cultivars in Upstate South Carolina

Interest in wine grape production is increasing in South Carolina, but Pierce’s Disease (PD) caused by the xylem-limited bacteria Xylella fastidiosa (Xf) is a major limiting factor. Xf is spread by sap-sucking insect vectors in the Cicadellidae family such as sharpshooters. In the United States, Xf has become endemic to the southeast as global temperatures rise, causing winter temperatures to increase, which allows the bacteria to survive year-round. However, PD-resistant grapevine hybrid cultivars have become available through breeding V. vinifera genes with native American Vitis species that are resistant to Xf. In this study, the PD-resistant grapevine hybrid cultivars were evaluated at a research farm in Upstate, SC for fungal disease susceptibility and performance under a water deficit through disease scouting and induced drought experiments. The study showed that 1) PD-resistant hybrid cultivars were susceptible to diseases such as powdery mildew and downy mildew and 2) some PD-resistant hybrid cultivars such as ‘Ambulo Blanc’ and ‘Errante Noir’ were more susceptible to a water deficit than other PD-resistant hybrid cultivars, based on a potted experiment on 1-year old grapevines.