Identifying the Potential to Use Vineyard Water Status to Alter Anthocyanins and Other Phenolic Compounds in Red Winegrapes

The first of two main objectives in this project is the separation and analysis of the phenolics present in approximately 300 fruit samples of Cabernet Sauvignon that were obtained from vines grown near Lodi and subjected to various irrigation regimes. The major phenolic compounds that change in concentration during ripening were identified by HPLC and comparison to standards. We identified approximately 20 compounds in skin extracts and juice samples that are of potential interest because of significant responses to changes in vine water status. These are categorized into phenolic classes, cinnamates, flavonols, and anthocyanins on the basis of their absorption spectra. For those compounds identified as present in significant concentrations, the seasonal pattern, the relationship of the concentration to the accumulation of sugars in the berry, and changes in these patterns caused well-defined differences in vine water status that were imposed before and after veraison were analyzed. The second specific objective was the establishment of a new field trial in a commercial Cabernet Sauvignon vineyard located in the North Coast. A field trial was established in a mature, uniform vineyard in Knight’s Valley on a light soil in which five irrigation regimes can be imposed that create early season water deficits and varying degrees of late season water deficits. The late ripening at the site will facilitate extended seasonal analysis of phenolic responses to vine water status.