MULTI-LOCUS SEQUENCE TYPING (MLST) TO IDENTIFY RESERVOIRS OF XYLELLA FASTIDIOSA DIVERSITY IN NATURAL HOSTS IN CALIFORNIA

• Author(s): Cooksey, Donald; Luck, Robert; Nunney, Leonard; Stouthamer, R; Vickerman, Danel;
• Abstract: The ability to identify accurately and track the strains of an important infectious agent causing a plant disease is fundamental to the surveillance and management of that disease. Therefore, it is critical that we determine what type of Xylella fastidiosa (Xf) disease reservoir exists in uncultivated habitats and identify potential new variants of Xf and their host plants. Our plant collection and xylem extraction efforts have targeted native and naturalized plants in riparian habitats that may harbor Xf which is spread from cultivated plants such as grapes by infected blue green sharpshooter (BGSS), Graphocephala atropunctata (Signoret) as they move from the riparian vegetation into the vineyards and adjacent plant communities (Purcell 1975). In order to detect and characterize the Xf strains from field collected plants, we have first developed a protocol using the real-time polymerase chain reaction (PCR), which has been proven to detect Xf at much lower levels than is possible with traditional PCR, and is a one step process reducing the possibility of error (Oliveira et al. 2002, Bextine and Miller 2005). Furthermore, we are using a technique for whole genome amplification which allows us to boost the amount of DNA in low concentration samples so that traditional PCR can be used to amplify and sequence a series of genes. We have detected Xf and determined the strain in several common native plant species, including Encelia farinosa (brittlebush), Xanthium strumarium (cocklebur), Salvia mellifera (black sage), Pluchea odorata (sweetscent) and Vitis girdiana (wild grape). This information is essential for fully understanding the potential for recombination and the generation of new strains. The results of this project will allow for a rational control of the pathogen by either planting or removing particular host plants in the proximity of the Xf reservoirs.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium