1a.Objectives (from AD-416)
1. Sequence whole genomes for at least 3 PVY-N:O strains that do not cause tobacco vein necrosis, and analyze their sequences against at least 3 other PVY-N:O strains that do.
2. Sequence whole genomes for at least 3 PVY isolates that cause tuber necrosis in potato and analyze their sequences against at least 3 other PVY strains that do not.
3. Express PVYO and O5 capsid proteins in bacteria and correlate the monoclonal 1F5 reactivity with the point mutation in the PVY-O capsid protein.
1b.Approach (from AD-416)
Potato virus Y isolates collected by State Potato Seed Certification agencies and partially characterized by either State laboratories or the ARS laboratory at Ithaca, NY will be sent to the University of Idaho. Virus genomes will be amplified using a RT-PCR protocol and the products sequenced. Sequence information will be catalogued in a bioinformatics database that will be made available to all collaborators on the project. Virus protein fragments will be expressed in bacteria and used to characterize epitopes that recognize monoclonal antibodies.
Potato virus Y is the most economically important disease affecting the US seed potato industry. In recent years several new strains of the virus have been discovered in the US many of which cause severe necrosis in potato and tobacco and these are a threat to commercial production. State and federal regulatory agencies, and their equivalents in international trade partners, test for these necrotic strains of PVY strains using antibody based lab tests that are relatively quick and simple. We discovered a new variant of PVY that is identified as a necrotic strain by these antibody based lab tests, but this variant actually poses no threat since it does not cause necrosis in the host plant. However, detection of this virus variant has led to several shipments of potatoes being refused at border checkpoints and/or being destroyed rather than being sold. In this paper we characterized the new virus variant and determined that a minor change in one virus protein allows the virus to react with the antibody currently used to detect necrotic strains of PVY. This simple change in one protein does not affect any other property of the virus. We have tested other commercially available antibodies and identified one that does not identify this variant as a necrotic virus, but it does recognize the real necrotic viruses as such. A simple change in testing procedures used by regulatory agencies can avert these erroneous results and facilitate trade of potatoes across state and international boundaries. Currently the North American Plant Protection Organization is revising its PVY testing protocols based on our research findings. Progress was monitored through email and phone conversations.