GLASSY-WINGED SHARPSHOOTER TRANSMISSION OF XYLELLA FASTIDIOSA TO ALMOND

• Author(s): Purcell, Alexander; Almeida, Rodrigo;
• Abstract: The acquisition of Xylella fastidiosa (Xf) from dormant almond by the glassy-winged sharpshooter (GWSS) was attempted in January 2003 near Bakersfield with 16 groups of 4 adult GWSS per group caged on branches of almond trees with ALS symptoms and confirmed by culturing as having Xf infections. None of the surviving GWSS transmitted Xf to 16 Non-pareil almond test plants. Culture assays for Xf in naturally-infected field almonds and greenhouse plants documented densities of about 1,000,000 to 10, 000,000 live Xf per gram of leaf vein. These are 10 to 100 times lower than in grapes with PD symptoms and may explain in part why vector acquisition of Xf from almond is lower than from grape. In other experiments, we found that previously reported, genetically-determined groupings of Xf strains from almond (Groups I and II) and grape or almond (typed as Grape strains) had distinctive biological characteristics that corresponded to the genetic groupings. All strains mechanically inoculated into grape and almond caused almond leaf scorch (ALS), but only grape strains caused Pierce's disease. Almond Group I strains did not grow on PD3 medium, but Almond Group II strains and Grape strains did. Almond strains of Xf survived winter dormancy in almond at Berkeley better than did grape strains, but the reverse was true in grape.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium