SHARPSHOOTER FEEDING BEHAVIOR IN RELATION TO TRANSMISSION

• Author(s): Backus, Elaine; Bennett, William; Civerolo, Ed; Groves, Russell; Habibi, Javad; Joost, P.; Morgan, David; Shugart, Holly;
• Abstract: Progress this year consisted of completing past projects as well as building infrastructure for future research. Backuss new lab in Parlier was renovated, upgraded and equipped with state-of-the-art facilities for electrical penetration graph (EPG) monitoring of insect feeding and histology of plant and insect tissues. Extensive colonies of glassy-winged, smoke tree, green, and red-headed sharpshooters were established in Fresno and Parlier (with R. Groves, ARS Parlier). New personnel were hired; data was intensively analyzed and grant proposals written. Much effort was also expended in developing new protocols and preliminary findings for feeding waveform correlations with bacterial expulsion and muscle contraction, as well as AC and DC waveforms for several species in colony. Stylet activities and salivary sheath-cell type correlations for the major GWSS waveforms were completed (Objective 1), as was all of the plant histology for the GWSS inoculation test (Objective 2). Results to date support a modified version of last years hypothesis for the mechanism of Xf inoculation to grape. Xf bacteria may exit the stylets during brief stylet activities represented by the B1spikelet burst, B1-like portions of N and/or C, probably within seconds of the first puncture of any penetrated cell, both along the pathway to and within xylem. Proper placement of the bacteria appears to be crucial; placement in xylem leads to growth of the bacteria sufficient for detection by less sensitive methods such as culturing. Otherwise, when more sensitive detection methods such as immunocytochemistry of the tissues immediately surrounding the salivary sheath are used, they can detect Xf in non-xylem tissues. Three papers from this research are in preparation for submission in late 2004 early 2005. This work will help solve the PD/GWSS problem by identifying the mechanism of Xf inoculation and crucial aspects of inoculation efficiency, and eventually aid host plant resistance through the development of the Stylet Penetration Index.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium