2008 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 is the second year of a multi-year project and already we are seeing some progress. The crop yield data showed that own-rooted Chardonnay tended to have greater yields than grafted vines, while no clear differences were observed for Merlot. Own-rooted Syrah had the lowest yields and 3309-Syrah grafts were the highest. For Chardonnay and Merlot the rootstocks did not influence sugar and color accumulation, nor the rate of acid decline. As a contrast, own-rooted Syrah ripened fastest, and Syrah-140-2 had significantly lower color. Own-rooted Chardonnay and Merlot consistently had the highest pH during ripening. For the finished wines, own-rooted Chardonnay had the highest pH and lowest titratable acidity. For the most part, Merlot wines showed no differences except 1103P and 140R, which had the greatest titratable acidity. Own-rooted Syrah had the highest pH and second highest titratable acidity while Syrah grafted to 3309 had the lowest pH and highest titratable acidity. In contrast to last year, all of the rootstock scion combinations were high in proline and low in arginine. Only Syrah had significant amounts of arginine and had relatively lower amounts of proline than the other two varieties. The wines were made under modest conditions (25 gallon garbage cans) and moderate success was gained throughout the process. Within a variety, there were no observed differences in the alcohol concentration for any of the wines produced. All of the red wines were evaluated for their tannin, anthocyanins, and total iron reactive phenolics content at pressing. The results show that for Merlot there are no significant differences between any of the phenolic components. For Syrah there were no significant differences for the tannins and total phenolics; however, some small detectable differences were seen with anthocyanins. The rootstocks 101-14, 1103 P, and 5C had significantly greater anthocyanins than the other rootstocks and own-rooted vines. We did not observe greater concentrations in polymeric pigments for any of the Syrah wines (data not shown). It is well known that polymeric pigments are formed via reactions with tannins and various other phenolics and organic acids. The lack of greater polymeric pigments in the wines with significantly greater anthocyanin concentrations suggests that tannin and total iron reactive phenolics, which were not different, play a significant role in polymeric pigment formation. Thus, to stabilize pigment you must have greater amounts of tannins to stabilize the color; otherwise, it may be lost. Generally, Syrah had significantly greater concentrations of anthocyanins than Merlot wines but also had significantly less tannin and iron-reactive phenolics than the Merlot wines. In the current season, we will be making separate lots of wine from each scion/rootstock combination. We also hope to demonstrate if differences exist in wines made from such combinations and, in particular, if grafting is able to alter wine composition and if significant differences exist sensory analysis will be performed. Methods of ADODR monitoring included meetings, e-mail, and phone calls.