IDENTIFICATION OF MECHANISMS MEDIATING COLD THERAPY OF XYLELLA FASTIDIOSA- INFECTED GRAPEVINES

• Author(s): Kirkpatrick, Bruce; Meyer, Melody;
• Abstract: Pierces disease does not occur in colder regions of North America. Although the cold curing phenomenon has been well documented, little is known about the physiological mechanisms that mediate cold therapy. To better understand the cold therapy phenomenon, we planted control and Xylella fastidiosa (Xf) infected Vitis vinifera Pinot Noir (PN) and Cabernet Sauvignon (CS) grapevines across 4 locations in Northern California and exposed control and infected grapevines across 4 temperature conditions in cold rooms. After treatment periods, xylem sap was extracted using a pressure bomb and the composition of the sap was analyzed for pH, osmolarity, glucose, sucrose, fructose, Ca(2+), and Mg(2+). Differences were found across the different field locations and cold rooms. Similar results for CS inoculated vines were found for the cold room experiments. Results for the PN field plots revealed differences in pH for both inoculated and control vines across the field plot locations. Osmolarity values of PN control vines were different across the field plot locations and in the cold room treatments. Effects of buffer and xylem sap on the survival of Xf and various cold temperatures were reported in the 2004 PD/GWSS Proceedings. Abscisic acid (ABA) levels are elevated in many cold-treated plants and ABA has been shown to induce the synthesis of certain pathogenesis related (PR) proteins that in some case possess anti-fungal properties. However, we are proceeding with experiments to determine if exogenous applications of ABA on non-chilled grapevines can elicit PR proteins.
• Publication Date: Nov 2006
• Journal: 2006 Pierce's Disease Research Symposium