DOCUMENTATION AND CHARACTERIZATION OF XYLELLA FASTIDIOSA STRAINS IN LANDSCAPE HOSTS

• Author(s): Cooksey, Donald; Costa, Heather; Wong, Frank;
• Abstract: Strains of Xylella fastidiosa (Xf) were characterized using random amplified polymorphic (RAPD)-PCR and sequence analysis of the 16S-23S rDNA intergenic spacer regions (ISR). Results indicated that all mulberry leaf scorch (MLS) strains and the heavenly bamboo strain formed a cluster. Strains isolated from daylily, jacaranda and magnolia clustered with the Xf subspecies sandyi; strains isolated from spanish broom, a redbud strain, two new peach strains and several almond strains clustered with Xf subspecies fastidiosa, and the oak strains formed a separate cluster. Predicted members of the Xf subspecies multiplex were the strains isolated from purple leafed-plum, olive, peach, plum, some almond, sweet gum, maidenhair tree, crape myrtle and one redbud. Pathogenicity of MLS strains was demonstrated in glasshouse assays by stem inoculating mulberry, grape and oleander with Xf isolate morus059 grown for 7 days on PW. Three months post-inoculation, only inoculated mulberries exhibited leaf scorch symptoms and bacteria were recovered from most of the inoculated mulberries but not from oleander or grape. Given that strains isolated from magnolia (MG038), jacaranda (JM028), and daylily (HEM034) always grouped with oleander strains, we tested their ability to produce disease in oleander and grape. The three strains MG038, JM028, and HEM034 caused oleander leaf scorch (OLS) but not Pierces disease (PD) symptoms and bacteria were re-isolated from oleanders that were diseased. This study served as a confirmation of our genetic results, as well as an indirect demonstration that the Xf subspecies sandyi might be found in other hosts than oleander. More cross inoculation experiments are underway.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium