Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2009
Publication Date: 8/1/2009
Citation: Backus, E.A., Morgan, D. 2009. Patterns of spatial colonization of Xylella fastidiosa in the foregut of glassy-winged sharpshooter support egestion as part of the mechanism of inoculation. American Phytopathological Society Annual Meeting. 2009 Supplement: S6.
Technical Abstract: There has been an increase in incidence of Pierce’s Disease in California following introduction of the glassy-winged sharpshooter (GWSS), a vector of Xylella fastidiosa (Xf). Although host plant resistance to the bacterium and/or GWSS is being sought, research is hampered by lack of understanding of vector acquisition and inoculation processes. During acquisition, Xf colonizes the anterior foregut(precibarium and cibarium). Subsequent inoculation of Xf occurs by an unidentified feeding process. Previous research supports the hypothesis that inoculation occurs through salivation combined with egestion, i.e. outward flow of fluid from the precibarium. To test this hypothesis, we studied colonization of the precibarium and cibarium by green fluorescent protein (GFP)-expressing Xf over 1 to 6 day acquisition access periods (AAP’s) of GWSS on infected grape. Field-collected GWSS (heavily colonized by non-GFP Xf prior to the AAP) were compared with clean, lab-reared GWSS (not colonized prior to the AAP). After the AAP, confocal laser scanning microscopy was used to visualize GFP-Xf in situ within the undissected foregut. Fine structure of Xf colonies was examined via scanning electron microscopy. Lab-reared GWSS acquired large amounts of GFP-Xf, first into the cibarium, then gradually into the precibarium. In contrast, field-collected GWSS acquired fewer GFP-Xf into areas of the precibarium critical for inoculation. Both groups of insects also showed de-colonization of the precibarium over time, with spatial patterns of colony retention suggesting physical flushing of the bacteria from walls of the precibarium via egestion.