ARS | Publication request: The transmission mechanism of Xylella fastidiosa by sharpshooter vectors and a model for quantification of vector efficiency

Submitted to: Entomology Society of America Pacific Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2008
Publication Date: March 30, 2008
Repository URL: http://groups.ucanr.org/pbesa/files/50028.pdf
Citation: Backus, E.A. 2008. The transmission mechanism of Xylella fastidiosa by sharpshooter vectors and a model for quantification of vector efficiency [abstract]. Entomology Society of America Pacific Branch Meeting. p.52.

Technical Abstract: The exact mechanism of transmission (acquisition and inoculation) of Xylella fastidiosa (Xf) by sharpshooter vectors such as the glassy-winged sharpshooter, Homalodisca vitripennis (Germar), has been unknown. This presentation will summarize five years of work to identify the transmission mechanism in terms of fluid flow into and out of the vector’s alimentary canal, especially the area termed the precibarium. It will also present a model of four critical steps to assure success in the acquisition and inoculation process. The first step is whether Xf bacteria are acquired into a clean precibarium or one already occupied by competing. non-Xf bacteria. The second step is whether bacteria colonize a specific location within the precibarium, from which they are dislodged during feeding. The third step is performance of a specialized inoculation behavior that consists of salivation, ingestion of mixed saliva and plant fluid, followed by two different types of egestion, each from a different area of the precibarium. Thus, the mechanism of inoculation is a combination of salivation and egestion. These behaviors have been correlated with electrical penetration graph (EPG) waveforms, which are used to measure durations and how often they are performed. The fourth step is whether inoculation behaviors are performed in a xylem cell. We can quantify each of these steps, and determine an overall percent transmission efficiency score. Future work will use this quantitative model to compare transmission efficiencies among various strains of Xf, such as the virulent Temecula strain vs. EB92-1, the benign biocontrol strain of Hopkins.