2007 Annual Report 1a.Objectives (from AD-416) 1) Evaluate whether rootstocks alter winegrape fruit composition during ripening and at harvest compared with winegrapes grown on their own roots. 2) Test for interactions between winegrape variety (scion) and rootstock in terms of fruit composition. 1b.Approach (from AD-416) Conduct a field experiment with three winegrape varieties (Merlot, Syrah, Chardonnay) that are either grown on their own roots or grafted to six different rootstocks. Fruit samples will be collected weekly from veraison through harvest from each variety/rootstock combination, weighed and analyzed for soluble solids, pH, titratable acidity, and color using standard laboratory practices. Documents Grant with Washington State University. 3.Progress Report This report serves to document research conducted under a grant 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. Dr. Harbertson and collaborators conducted the following research towards the agreements objectives: Own-rooted Chardonnay tended to have higher yields than grafted vines, while no clear differences were found for Merlot, and own-rooted Syrah had the lowest yields and Syrah grafted to 3309 had the highest. The rootstocks had no influence on sugar and color accumulation and acid degradation in Chardonnay and Merlot. On the other hand, sugar accumulation was fastest on the (undercropped) own-rooted Syrah, and less color accumulated on Syrah grafted to 140-2. Throughout ripening, Chardonnay and Merlot, but not Syrah, consistently had the highest pH on their own roots (Merlot also on 101-14) and the lowest on 140-2. The color of Merlot juice decreased as berry size increased, but this was not true for Syrah. Although there was no significant rootstock effect on juice potassium (K+) content, the difference in pH between and within varieties was in large part explained by variations in K+ rather than titratable acidity: Merlot contained the most and Chardonnay the least K+. Proline and arginine were by far the dominant amino acids present in grape juice, and there were marked differences among varieties: Merlot juice was high in praline but low in arginine, Syrah was low in proline but high in arginine, while Chardonnay was low in both amino acids. Juice from own-rooted Chardonnay and Syrah, but not Merlot, contained considerably more arginine than did juice from grafted vines. This is of practical significance, since musts deficient in arginine may result in sluggish or stuck fermentations. Grafting did not affect juice proline. In the current season we will be making separate lots of wine from each scion/rootstock combination. We hope to demonstrate if differences exist in wines made from such combinations and, in particular, if grafting is able to alter wine composition and sensory perception. Therefore, wines will be made for three years, and sensory analysis will be performed along with chemical analyses of these wines. ADODR Statement: The ADODR met with the cooperating PI and project personnel at meetings during the year and discussed results through phone calls, e-mail, and in person.