|Joost, P - UNIV OF CALIF-RIVERSIDE|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 25, 2006
Publication Date: March 17, 2006
Citation: Backus, E.A., Shugart, H., Joost, P.H. 2006. Electrical penetration graph (epg) monitoring of feeding behavior of the glassy-winged sharpshooter, and its use in understanding the transmission of the Pierce's Disease bacterium, Xylella fastidiosa. [abstract]. AgBiotech 2006 A Central California Agricultural Biotechnology Conference. P.17. Technical Abstract: Xylella fastidiosa (Xf) is a xylem-limited, insect-vectored, plant bacterium that causes various scorch and wilt diseases in crop plants, the most notorious of which is Pierce’s Disease (PD) of grape. The most economically important vector is a recently invasive, exotic species, the glassy-winged sharpshooter (GWSS), Homalodisca coagulata. Coordinated scientific efforts are underway to develop varieties of grape that are resistant to PD. We use electrical penetration graph (EPG) monitoring to directly observe and quantify feeding of GWSS on grape. In combination with confocal microscopy of Xf transformed to express green fluorescent protein (GFP), we are identifying the precise "inoculation behavior". The performance of this behavior will be compared among different grape (and other host plant) genotypes, to develop a mathematical model that will be used as a resistance index for rapidly screening grape genotypes (via EPG) for resistance to natural inoculation. We have also developed the first method for standardized vector inoculation, and are using it to trace the complete process of natural inoculation, systemic infection, and symptom development. We allow a single, GFP-Xf-inoculative GWSS to perform one, standardized inoculation event (EPG-recorded) on each of a set of healthy plants, then hold each plant for varying time periods before analyzing for the location of GFP-Xf. This talk will provide background on EPG and the waveforms that represent various GWSS feeding behaviors. Data will be presented that support that the B1, C and N waveforms are involved in inoculation, and may all contain the inoculation behavior. Also, Xf can be detected via PCR both locally, in the vicinity of the inoculating probe, and systemically, at petiole sites very distant from the probe. Implications for the inoculation mechanism will be discussed.