Recently, there has been an increased interest in wine grape (Vitis vinifera) production in South Carolina (SC). The warm and humid climate in SC creates a conducive environment for a high risk of disease incidence. Despite the typical climate, SC has droughts periodically. Pierce’s Disease (PD), caused by the xylem-limited bacterium Xylella fastidiosa (Xf), is a major limiting factor to grapevine cultivation throughout the United States and, specifically, in the southeastern U.S. However, PD-resistant grapevine cultivars have been released by UC Davis. Xf-infected grapes can be heavily influenced by water deficit. Preliminary data from a drought-stress experiment in the Summer of 2023 indicated two PD-resistant cultivars perform well under a water deficit. The objective of this study was to evaluate the water dynamics and gas exchange of PD-resistant cultivars during periods of drought. In March 2023, five PD- resistant cultivars and one French-American hybrid were planted in a variety trial at Musser Fruit Research Center in Seneca, SC. The drought-stressed PD-resistant ‘Paseante Noir’ and ‘Errante Noir’ had similar carbon dioxide assimilation to well-watered PD-resistant cultivars. PD-resistant cultivar ‘Ambulo Blanc’ showed the worst leaf water status and lowest carbon dioxide assimilation when stressed. In 2024, physiological measurements, such as sap flow, trunk diameter, gas exchange, and water potential, were taken throughout the growing season. Our results supported previous research that some PD- resistant grapevine cultivars perform well in the field under drought conditions.
