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Pierce's Disease
Research Updates

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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

THE UTILITY OF THE INTERNAL TRANSCRIBED SPACER REGION 2 (ITS2) IN CONFIRMING SPECIES BOUNDARIES IN THE GENUS GONATOCERUS: COMPARISON TO THE CYTOCHROME OXIDASE SUBUNIT I (COI) GENE AND TAXONOMIC DATA: MOLECULAR KEY BASED ON ITS2 SIZES

  • Author(s): de Le?n, Jesse; Logarzo, Guillermo; Triapitsyn, Serguei; Morgan, David;
  • Abstract: We sequenced the nuclear ribosomal internal transcribed spacer region 2 (ITS2) from several glassy-winged sharpshooter (GWSS) [Homalodisca vitripennis Germar (=H. coagulata Say)] egg parasitoid species (Hymenoptera: Mymaridae) belonging to the genus Gonatocerus Nees to test the utility of this fragment to confirm species boundaries and to define phylogenetic relationships. A total of 35 specimens belonging to 10 named species, one unnamed species, and two specimens from another mymarid genus (Anagrus erythroneurae) (outgroup) were analyzed. A phylogenetic tree generated using the neighbor-joining algorithmic method showed that each named Gonatocerus species formed its own unique taxonomic unit or clade with very strong bootstrap support (100%), confirming species boundaries. The ITS2 fragment confirmed species boundaries as well as cytochrome oxidase subunit I (COI) sequence data. Furthermore, the phylogenetic relationships among species generated by the ITS2 fragment were in excellent agreement with those delineated by taxonomic data. The current results clearly confirm the utility of the ITS2 fragment in confirming species boundaries of egg parasitoids beloning to the genus Gonatocerus. The results showed that the ITS2 fragment appears to be phylogenetically more informative or valuable than that inferred by COI sequence data. Since several important Gonatocerus species were analyzed, a molecular key based on ITS2 sizes was developed. In the event two species (e. g., G. ashmeadi and G. metanotalis and G. walkerjonesi and G. annulicornis) were found with similarly sized ITS2 fragments, inter-simple sequence repeat-polymerase chain reaction (ISSR-PCR) DNA fingerprinting was performed to distinguish them. ISSR-PCR very clearly distinguished the aforementioned species, demonstrating that it is an excellent molecular diagnostic tool. The current results are important to the biological control program in California.
  • Publication Date: Nov 2006
  • Journal: 2006 Pierce's Disease Research Symposium

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