2007 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project is to conduct collaborative viticulture research of mutual benefit to ARS and the University of Idaho. The research conducted by the University of Idaho will be complementary to the wine grape research program established by ARS at the University of Idaho’s Parma Research and Extension Center. The broad objective of the ARS program is to investigate integrated, sustainable production practices for development of improved vineyard management strategies and improved end product quality or perceived market value. 1b.Approach (from AD-416) Investigate critical management and production practices impacting wine grape quality components. Emphasis will be placed on water and canopy management, end-product processing methods, as well as germplasm evaluation. Documents SCA with U of ID - Parma. 3.Progress Report This report serves to document research conducted under a specific cooperative agreement between ARS and the University of Idaho. 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. The following research was conducted towards the agreements objectives: Matching germplasm to site location is a fundamental viticultural practice to enhance yield and fruit quality. Results were published this year from a multiyear study investigating the viticultural performance of a diverse collection of leading red and white-skinned wine grape cultivars in southwestern Idaho. Yield and berry quality components were evaluated over four consecutive growing seasons. Red and white-skinned wine grape cultivars from Austria, France, Germany, Hungary, Italy, Portugal, Spain, and South Africa were evaluated in Parma, Idaho USA, and results compared to published data from warmer and cooler production sites. Vine yield components, fruit composition, and vegetative growth parameters were used to describe relative cultivar performance based on crop load and fruit maturity. Information from this research can be used to aid cultivar selection for new planting sites by comparison of heat unit accumulation and frost-days to the site of evaluation for this study. Little information has been published on the response of Merlot grapevines to water stress under field conditions, and none is available on their response to deficit irrigation under the climatic conditions and soils of southwestern Idaho. The objective of this research was to measure vine and berry response of Merlot grown to differing severity of vine water stress during berry development. Own-rooted Merlot vines were exposed to deficit irrigation treatments in a 3-year field trial conducted in the warm, arid Western Snake River Plain of southwestern Idaho. Vines were drip irrigated weekly with 100, 70, or 35% of their estimated required water. A fourth irrigation regime provided 35% of water needs until berries changed from green to purple, and then 70% of estimated needs until harvest. Vine water stress was monitored weekly and corresponded with amount of irrigation. Decline in main shoot growth, berry size, cluster weight, yield, trunk growth, cluster number, and berry titratable acidity corresponded with a decline in vine water status. Increasing irrigation amount from 35 to 70% at veraison produced the same yield and fruit quality as 70%, but increased water savings by about 25%. During the next year of this project we plan on beginning to characterize cultivar differences in response to deficit irrigation with the ultimate goal of identifying an optimum level of vine water stress for different cultivars. Optimum response will be based on grape composition as well as yield, vine health, and water use efficiency. ADODR Statement: The ADODR discussed results through phone calls, e-mail, and in person.