EVALUATION OF A NOVEL, FIELD DEPLOYABLE, ELECTROCHEMICAL DETECTION SYSTEM FOR THE DETECTION OF XYLELLA FASTIDIOSA WITHIN GRAPEVINE PETIOLES

• Author(s): Lam, Vien; Morano, Lisa;
• Abstract: We have tested a new electro-chemical detection (ECD) system designed by AnzenBio, Inc. for the quick detection of Xylella fastidiosa within grapevine petioles. Like standard ELISA this detection method relies on antibodies against the bacterium, but unlike ELISA it detects movement of electrons through the final product conversion, measuring current rather than color change. Using a hand-held meter and pre-coated chips the test can be done in a fraction of the time (1.5 vs. 5 hrs.). Comparison of 18 Cabernet Sauvignon petioles from a vineyard with Pierces disease (PD) to 18 petioles guaranteed PD free showed the ECD readings per gram of tissue to be higher for PD petioles (31.3 vs. 6.2 microamps). This difference is statistically different using a t-test (p<0.0001). In another trial in South Texas, ECD was used to evaluate the petioles from three different varieties, Blanc du Bois, Black Spanish and Cynthiana, which have been shown to carry differing levels of Xylella fastidiosa within this area of high PD pressure. Petioles were also categorized into those from leaves with low, medium and high PD symptoms. Analysis of variance on ECD data from the 9 symptom variety categories with 6 replications showed that ECD could detect distinct significant differences between several of the categories (p<0.0001). Analysis of variance on ELISA data run on the same 54 samples found no significance between categories (p=.43). ECD appears to give more sensitive readings over a range of bacterial levels, potentially giving fewer false positives.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium