Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: 10/12/2006
Publication Date: 11/27/2006
Citation: Backus, E.A. 2006. Where, when and how do ingestion and other feeding behaviors of the glassy-winged sharpshooter allow inoculation of Xylella Fastidiosa [abstract]. CDFA Pierce's Disease Control Program Research Symposium Proceedings. p252. Interpretive Summary: Feeding of the glassy-winged sharpshooter (GWSS) on plants was monitored by recording changes in electrical waveforms generated by specific stages of insect feeding. This year, we identified a diagnostic electrical pattern (waveform C) associated with ingestion of plant xylem fluid by the GWSS. We also demonstrated that another electrical waveform (B1) represents in-and-out movement of fluid caused by fluttering of the GWSS precibarial valve inside the insect’s foregut. This fluid movement probably contributes to expulsion of bacteria from the foregut during feeding, as the foregut is the site where bacterial colonies of Xylella fastidiosa (Xf) reside in the GWSS. We also learned that the precibarium is the first area in the GWSS colonized by Xf when bacteria are ingested from the plant. Both amount and location of Xf in the foregut of the GWSS determine subsequent efficiency of Xf inoculation to plants. These results provide new information concerning mechanisms involved in GWSS feeding on plants and provide new insights concerning transmission of Xf by the GWSS vector.
Technical Abstract: This year, we completed the laboratory portion of work that identified an aspect of electrical penetration graph (EPG) ingestion waveform (C) of glassy-winged sharpshooter (GWSS) that definitively represents xylem ingestion. We also demonstrated that extravasation is correlated with the B1 waveform. Both B1 and C waveforms may play a role in the behavior that facilitates inoculation of Xylella fastidiosa (Xf). Results this year support that both amount and location of Xf binding in the foregut of GWSS ("vector load") are critical for success of subsequent inoculation. The precibarium is the first area colonized during acquisition, and also may be the most important location for subsequent inoculation. If insects become "maximally loaded" with Xf, preliminary results suggest that a single probe by a single vector can cause a lethal infection of grapes. These results will help solve the Pierce’s disease/GWSS problem by describing mechanisms of vector feeding and pathogen transmission and providing new potential targets for host plant resistance.