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United States Department of Agriculture

Agricultural Research Service

Research Project: EFFECTS OF CLUSTER ZONE LEAF REMOVAL ON NORISOPRENOIDS OF PINOT NOIR FRUIT AND WINE, PART 1: CANOPY MICROCLIMATE AND FRUIT QUALITY
2011 Annual Report


1a.Objectives (from AD-416)
1. Determine the impact of cluster zone leaf removal in modifying microclimate for fruit quality in both high and low vigor vines. 2. Evaluate impacts of microclimate on total phenolics and anthocyanins of Pinot noir. 3. Improve the understanding of leaf pulling on formation of norisoprenoids in Pinot noir grapes and wine in relation to inherent vine vigor. 4. Link vine vigor, leaf removal and composition to sensory characteristics of wines.


1b.Approach (from AD-416)
Study Pinot noir at two distinct locations in Oregon: a vigorous, dry farmed site (Willamette Valley) and a low vigor site (Southern Oregon). These vineyards will have the same cultivar and rootstock to reduce between site variability. The experimental vineyards will be monitored for vegetative growth, vine size and microclimate of treatments. Sunlight intensity measurements of the vine canopy in the cluster zone will be taken for all treatments concurrently. Vines will be monitored for photosynthetic efficiency. Vine microclimate will be monitored for light spectral quality and temperature throughout the season. At the end of the season, cluster weights and berry weights will be obtained to determine any treatment effects on fruit size. Shoot number per vine and cluster per shoot will be recorded during the growing season. Documents Grant with Oregon State University. Formerly 5358-12210-003-14G (8/2011).


3.Progress Report

A 3-year project began in 2010 to identify proper timing and intensity of crop thinning for production of high quality Pinot Noir fruit. At the same time a cluster-zone leaf removal experiment was also begun to determine impacts on fruit quality by modifying cluster exposure. The goal of this work is to come up with better metrics for the grape grower to use to determine adequate vine balance in cool climates such as Oregon.

Within the first year of this study, we have measured the impact of various timing of crop removal and leaf pulling on vine growth and fruit composition. The crop thinning treatments reduced total vine yield by 40 to 70% compared to non-thinned vines, but it did not increase fruit concentrations of sugars, total color or other quality-related compounds such as tannins and phenolics which are important for mouth-feel and overall wine sensory response. Leaving heavier yields until later in the season did not decrease vine growth of these vigorous vines, and the vines continued to be very vigorous, requiring just as much vine management as earlier crop-thinned vines. Therefore, there is little reason to wait until late in the season to crop thin if it is going to be conducted. Results indicate that there is no fruit quality effect of reducing yields in 2010. Vines were not over-cropped and a full crop load will not hurt the sustainability of the vines.

Within the first year of the leaf pulling trial (2010), we observed little benefit of leaf pulling in terms of fruit composition. While there were differences in cluster exposure with increased leaf removal, there were no differences in berry sugar, acid, tannin, phenolic or color composition. Leaf pulling at the trialed levels did not decrease vine growth and fruit ripening. While little difference was observed in this trial for basic fruit composition and vine growth, the impacts of leaf pulling may be beneficial for preventing fruit rots.

Further analysis of fruit in both the crop load and leaf pulling trials may yield differences in aroma compounds, such as norisoprenoids, which are still under analysis. Further field and lab research continues in 2011 and 2012 to provide additional data from which to draw more solid conclusions and develop metrics for grape growers to make informed decisions.

Methods of project monitoring included meetings, e-mail, and phone calls.


Last Modified: 12/22/2014
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