2010 Annual Report 1a.Objectives (from AD-416) Develop new monoclonal antibodies that can be used for rapid detection and identification of Potato virus Y (PVY) strains that can be utilized on a large scale by certification agencies, researchers, and diagnostic facilities. 1b.Approach (from AD-416) Nucleoproteins of diverse strains of PVY will be purified using standard methods. These will be used to immunize mice for production of monoclonal antibodies (MAbs) by hybridoma technology. The MAbs will be tested for virus strain specificity using a large panel of characterized PVY isolates available to the cooperator. Documents SCA with University of Idaho. Formerly 5354-21220-002-19S (5/08). 3.Progress Report The ordinary strain of Potato virus Y (PVY), PVYO, causes mild mosaic in tobacco and induces necrosis and severe stunting in several potato cultivars common in North America. There is, however, a growing body of evidence that PVYO strain group is not uniform both genetically and biologically. A novel sub-strain of PVYO was recently reported, PVYO-O5, spreading in the U.S. and distinguished from other PVYO isolates serologically, i.e. reacting to the otherwise PVYN-specific monoclonal antibody 1F5. To characterize this new PVYO-O5 sub-group, and address possible reasons for the continuing spread of this novel PVYO-O5 sub-type, we conducted biological and molecular studies of PVYO and PVYO-O5 isolates from the North American collection of PVY through whole genome sequencing and phylogenetic analysis. Forty-four PVYO isolates were sequenced, including 31 from the serologically defined PVYO-O5 group, and subjected to the whole genome analysis. Most of the serologically defined PVYO-O5 isolates formed a separate, PVYO-O5 lineage within the PVYO genome cluster in the whole genome phylogenetic tree. When tested on a set of potato cultivars, PVYO-O5 isolates induced systemic HR response in cultivars Desiree and Maris Bard carrying Ny gene, like other PVYO strains. However, this HR reaction was more severe and developed earlier than for other, ordinary PVYO isolates. Both PVYO and PVYO-O5 induced local lesions in Chenopodium amaranticolor, but their appearance was delayed for PVYO-O5. PVYO-O5 sub-type, thus, represents a novel evolutionary lineage of PVY from potato spreading in potato crops in North America. Progress on the project was monitored by email, phone conversations and by site visits. This project investigates the molecular and biological differences among isolates of potato virus Y which contributes directly to Objective 2 of the in-house project.