2013 Annual Report
1a.Objectives (from AD-416):
1. Determine the impact of cluster zone leaf removal in modifying canopy microclimate for fruit quality in both high and low vigor vines.
2. Improve the understanding of leaf pulling on formation of norisoprenoids in Pinot noir grapes in relation to inherent vine vigor.
3. Establish a correlation of grape aroma precursor content with wine aroma potential
1b.Approach (from AD-416):
Treatments will include 0, 50 and 100% leaves pulled in the cluster zone of the east side of the canopy of north-south oriented vine rows. A minimum of 10 vertically shoot positioned vines will be used per treatment rep with 5 replicates per treatment at each vineyard site. Leaf pulling will occur when fruit is in the bud break stage. Leaves will be removed from the base of the shoot up to the leaf subtending the uppermost cluster. Fruit will be thinned to the same number of clusters per vine at each site. The experimental vineyards will be monitored for vegetative growth, vine size and microclimate. At harvest, treatment replicates will be harvested separately. A 20 cluster sample will be collected per replicate for grape composition analysis. In addition, a minimum of 12 kg of fruit will be harvested per treatment replicate for wine production, wine components analysis and sensory evaluations. Documents Grant with Oregon State University.
This research was conducted in support of NP 305 objective 1 "Determine nutrient requirements to enhance product quality in woody perennial crops such as grapevine and rhododendron" of the parent project. High canopy density is common in the cool-climate winegrowing region of western Oregon. Excessive canopy density will produce unbalanced musts, resulting in poor wine quality. Basal leaf removal practices are common in many viticulture regions. Selective leaf removal in a grapevine canopy may improve fruit sunlight exposure, increase the photosynthetic activity of the remaining leaves and could positively influence fruit composition. In this study, the impact of three levels of leaf removal treatments, including 0% (Control), 50% and 100%, on sugar, acids, phenolics, and volatile composition of Pinot noir grapes as well as the impact on the aroma profile of final wines were studied. Basal leaf removal had no impact on grape total soluble solids, but decreased citric acid, and malic acid in 2012. Basal leaf removal significantly increased grape anthocyanin concentrations in 2010 and 2012. In addition, basal leaf significantly increased grape quercetin glycosides concentrations in all three years. Basal leaf removal management also affect the volatile composition in grapes. Basal leaf removal increased the concentration of glycosidically-linked cis-linalool oxide, trans-linalool oxide, linalool, alpha-terpineol, and geraniol. The total amount of terpene alcohol glycosides increased linearly with amount of leaf removal. From 2010 to 2012, basal leaf removal significantly increased the concentration of free and bound form ß-damascenone and the total C13-norisoprenoidsin grapes. Analysis of wine demonstrated that basal leaf removal at 50% and 100% level increased anthocyanins, linalool, methyl vanillate, ß-damascenone, as well as the potential ß-damascenone in wines, suggesting that the basal leaf removal can improve wine quality.