2004 Annual Report 4.What were the most significant accomplishments this past year? This report serves to document research conducted under a specific cooperative agreement between ARS and Washington State University. Additional details of research can be found in the report for the parent project 5358-21000-034-00D Production Systems to Promote Yield and Quality of Grapes in the Pacific Northwest. M. Keller, K. Eastwell and colleagues evaluated the impact of leaf-roll virus on grapevine productivity. Objective: Determine effects of leaf roll disease in several Vitis vinifera L. cultivars on the following plant responses that are related to vineyard productivity and fruit quality: vegetative growth, fruit set, rates of net carbon exchange, fruit maturation, fruit quality at harvest, and vine cold hardiness. Progress to date: A vineyard has been identified and established on-site at WSU-Prosser. The research blocks contains the wine grape cultivars Lemberger and Merlot. The latter block consists of virus-free 'Merlot' vines and vines infected with Grapevine leafroll associated virus-3 (GLRaV-3). The 'Lemberger' block contains virus-free vines and those infected with GLRaV-1 and/or -3. Since these are mature, fruiting vines and the virus status has been determined, measurement of physiological parameters can be initiated immediately. One of the difficulties in studying the effects of virus infection on different cultivars is the variability of viruses, particularly those that cause leaf roll disease. To make a comparison possible, virus-free clones from the NW Grape Foundation Block, representing six different cultivars, have been propagated and inoculated with a single source of GLRaV-3. These plants are being maintained in a shade house and successful infection will be confirmed by ELISA during the summer of 2004. This project and research material will form the basis of a Ph.D. student graduate research program; an acceptable candidate was not found in the pool of current applicants, so active recruitment has begun to identify a student.