WHERE, WHEN AND HOW DO INGESTION AND OTHER FEEDING BEHAVIORS OF THE GLASSY-WINGED SHARPSHOOTER ALLOW INOCULATION OF XYLELLA FASTIDIOSA?

• Author(s): Backus, Elaine; Bennett, William; Chen, Jianchi; Joost, P.; Miller, Thomas; Morgan, David; Shugart, Holly; Walker, Gregory;
• Abstract: Many nagging questions about the mechanisms of transmission of Xylella fastidiosa (Xf) by the glassy-winged sharpshooter (GWSS) exist, hindering development of predictive epidemiological models for ultimate GWSS impact on California crops, as well as rapid development of resistant crops. This new grant seeks to complete our answers to these questions. Only five months of funding from this grant was available to Backus this year, due to bureaucratic hurdles. Nonetheless, we were able to accomplish significant work with support from Backuss in-house ARS funds. Efforts focused on developing research infrastructure such as simultaneous availability of plants, insects and bacteria, and protocols for the experiments. We now receive monthly shipments of adult GWSS, housed in a CDFA-approved quarantine facility at CSU Fresno, fed on greenhouse-reared cowpea, sorghum and grape. We also maintain green fluorescent protein (GFP)-transformed Xf in colony and are mechanically inoculating it into grape (cv. Cabernet Sauvignon) on a regular basis. GWSS are caged on these acquisition plants for 6-8 days, and are assayed for presence and location of bacteria using protocols we developed for confocal laser scanning microscopy (CLSM). All protocols for electrical penetration graph (EPG)-monitoring of identified probes, including artificial termination of probes, marking of probe locations, and recovery of tissues and processing for CLSM, have been perfected. In addition, a protocol that was very difficult to develop has been nearly perfected, wherein a wired GWSS that has acquired GFP-Xf is monitored while probing transparent artificial diet. Views of its stylets and salivary sheath are simultaneously video-captured and synchronized with EPG waveforms. Preliminary results show that GFP-Xf is present and visually resolvable following injection by the stylets into artificial diet, but synchronization between video and EPG recording of behavior was not perfect in these earliest tests. The experiment to determine the time course of inoculation and movement of GFP-Xf from the site of injection is about to begin. However, completion of most of the other experiments will await start of a new post-doc in January 2006, to replace the previous post-doc after his departure from the project in May 2005.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium