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United States Department of Agriculture

Agricultural Research Service


Location: Horticultural Crops Research

2012 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.

3.Progress Report:

This research was conduction in support of objective NP 305 1B, Perennial Crops of the parent project. Canopy microclimate is important in determining fruit and wine composition. Excessive canopy density is known to produce unbalanced musts, resulting in poor wine quality. Canopy management, such as selective leaf removal in a grapevine canopy may increase the photosynthetic activity of the remaining leaves and can positively influence fruit composition. Cluster thinning, the removal of entire clusters from the vine is a common practice employed by grape growers. Cluster thinning is performed to increase the leaf area: fruit weight ratio in order to prevent over cropping, as well as to improve fruit size and composition. Earlier studies have shown that cluster thinning reduces fruit yield and increases the berry weight, soluble solids, and color of table grapes. While cluster thinning is a common practice, the impacts of the timing of cluster thinning on subsequent berry growth and fruit flavor composition have not been widely investigated. The main objective of the present study was to fill these gaps and to evaluate such effects in association with grape and wine aroma composition in Pinot noir grapes and wine.

High vegetative vigor is common in the cool-climate winegrowing region of Oregon, management strategies including leaf removal and crop thinning were investigated to reduce vine size and increase fruit quality of Pinot noir. Three leaf removal management practices were studied in 2010.

°Brix and organic acids are normally used as indicators for grape quality although they do not correlate well as grape aroma potential. Nevertheless, they are widely used as grape maturity indices. The major organic acids in grapes are malic and tartaric acids, and small amount of citric acid. Malic acid decreases with grape maturity. In 2010 and 2011, cluster zone leaf removal had no impact on grape °Brix, citric, tartaric, and malic acid content.

In order to evaluate grape quality, we analyzed three groups of compounds, including C6 aldehyde and alcohols, terpene alcohols and norisoprenoids based on their biological origins. Cluster zone leaf removal had no significant impact on C6 compounds, both free and bound in both years; no impact on free form terpineols in both years;and increased glycosidically bound terpene alcohols in 2010, but this trend was not observed in 2011.

As a UV protector, light plays very important role in carotenoids synthesis process in plants. Cluster zone removal can improve the light penetration and thus may have some impact on fruit carotenoid composition. Products of carotenoid degradation such as ionones, and damascenones are also important for wine flavor due to their low sensory threshold. The major carotenoids in Pinot Noir grape is ß-carotene and lutein although neochrome, neoxanthin, flavoxanthin and some unidentified carotenoids are also exist in small amount. In 2011, cluster zone leaf removal significantly increased the amount of neochrome a. and decreased the amount of flavoxanthin in grapes. However, lutein and beta-carotene was not influenced by leaf removal treatment. In 2010 and 2011, increasing trends were observed with free beta-damascenone as well as some glycosidically bound C13-norisoprenoids and total C13-norisoprenoids in grape grown under leaf removal treatment.

Last Modified: 4/16/2014
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