Pierce's Disease
Research Updates


What is Pierce's Disease?

Pierce's Disease is a bacterial infection, which is spread by bugs that feed on grapevines, particularly the "glassy winged sharpshooter." Grapevines that become infected with PD can quickly become sick and die.

glassy-winged sharpshooter

Xylella fastidiosa taxonomy

  • Author(s): Chang, Chung-Jan; Fatmi, M.; Lacy, G.; Postnikova, E.; Schaad, Norman;
  • Abstract: Xylella fastidiosa (Xf) is classified as a single species but genetic studies support multiple taxons. To clarify X. f. taxonomy, we used DNA homology (S1 nuclease procedure) and ITS sequencing to compare 26 strains from 10 hosts. Using stringent conditions (Tm-8 deg C), DNA homology revealed three taxons, with more than 70% homology. Taxon A (grape, alfalfa, maple, and two almond strains), taxon B (peach, elm, plum, wild grape, one almond, and sycamore strains), and taxon C (citrus strains) with mean homologies of 85, 82, and 87%, respectively. Mean reciprocal homologies between taxons A and B, A and C, and B and C, were 56, 39, and 46%, respectively. ITS results confirmed the same taxons; A and B, A and C, and B and C had similarities of 98.7, 97.9, and 99.2, respectively. Taxon A strains grow well on PD2 agar but B and C strains do not. Taxon B strains are susceptible to penicillin but resistant to carbenicillin and A strains are opposite. We propose taxons A, B, and C be named X. fastidiosa subsp. piercei, agglomeri, and idiotraposa, respectively.
  • Publication Date: Jun 2003
  • Journal: Phytopathology