2007 Annual Report 1a.Objectives (from AD-416) The overall objective is to survey the seed potato crop to establish baseline information on the incidence level of PVY and the strain composition of the virus population. 1b.Approach (from AD-416) State seed certification agencies are responsible for the collection of tubers and the initial serological testing to determine PVY and PVYN infection. Further characterization of up to 1000 isolates representing isolates from all seed producing states will include bioassays on tobacco and potato to determine if the virus causes necrosis, additional serological characterization and sequencing of genes known to be diagnostic for genetic and taxonomic classification. 3.Progress Report This final report serves to document research conducted under a Reimbursable Cooperative Agreement between ARS and APHIS that is funded by an APHIS grant. Additional information can be found in the annual report for 1907-22000-018-07G In response to the re-emergence of PVY and the identification of new, more damaging strains, the U.S. and Canadian governments and potato industries have developed the Canada/US-Management Plan for Potato Viruses that Cause Tuber Necrosis. An initial step in the implementation of this plan was a Bi-national Scoping survey of the seed potato crop to establish some baseline information on the incidence level of PVY and the strain composition of the virus population. Tuber samples were collected from all late generation potato seed fields in 17 seed production states in the fall of 2004, 2005, and 2006. Tubers were initially tested by ELISA for PVY infection and subsequently for the presence of necrotic strains of PVY. A systematic sample of PVY infected tubers from each state were subsequently tested using a variety of diagnostic methods to better distinguish the genetic diversity of the PVY isolates. Analysis of the 2004 and 2005 samples has been completed and the testing of the 2006 samples is ongoing. Results indicate that there is considerable genetic diversity among PVY isolates and that the diversity is not uniform across all seed potato production areas. The data also indicate that no one diagnostic method is capable of distinguishing all of the PVY strains present in the U.S. potato crop.