news and research about Pierce's Disease

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.

Xylella fastidiosa subspecies: x. fastidiosa subsp piercei, subsp. nov., x. fastidiosa subsp. multiplex subsp. nov., and x. fastidiosa subsp. pauca subsp. nov

  • Author(s): Fatmi, M.; Schaad, Norman; Postnikova, E.; Lacy, G.; Chang, Chung-Jan;
  • Abstract: Xylella fastidiosa, a fastidious bacterium Causing disease in over 100 plant species, is classified as a single species, although genetic studies support multiple taxons. To determine the taxonomic relatedness among strains of X. fastidiosa, we conducted DNA-DNA relatedness assays and sequenced the 16S-23S intergenic spacer (ITS) region using 26 strains from 10 hosts. Under stringent conditions (Tm -15 degreeC), the DNA relatedness for most X. fastidiosa strains was *70%. However, at high stringency (Tm -8 degreeC), three distinct genotypes (A, B, and C) were revealed. Taxon A included strains from cultivated grape, alfalfa, almond (two), and maple, interrelated by 85% (mean); taxon B included strains from peach, elm, plum, pigeon grape, sycamore, and almond (one), interrelated by 84%; and taxon C included only strains from citrus, interrelated by 87%. The mean reciprocal relatedness between taxons A and B, A and C, and B and C, were 58, 41, and 45%, respectively. ITS results also indicated the same grouping; taxons A and B, A and C, and B and C had identities of 98.7, 97.9, and 99.2%, respectively. Previous and present phenotypic data supports the molecular data. Taxon A strains grow faster on Pierces disease agar medium whereas B and C strains grow more slowly. Taxon B and C strains are susceptible to penicillin and resistant to carbenicillin whereas A strains are opposite. Each taxon can be differentiated serologically as well as by structural proteins. We propose taxons A, B, and C be named X. fastidiosa subsp. piercei, subsp. nov, subsp. multiplex, subsp. nov., and subsp. pauca, subsp. nov., respectively. The type strains of the subspecies are subsp. piercei ICPB 50025 (=ATTC 35879T and ICMP 15197), subsp. multiplex ICPB 50039 (= ATTC 35871 and ICMP 15199), and subsp. pauca ICPB 50031 (= ICMP 15198).
  • Publication Date: May 2003
  • Journal: Systematic And Applied Microbiology