|Cohen, Seth -|
|Kennedy, James -|
Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 4, 2012
Publication Date: March 27, 2012
Citation: Cohen, S., Tarara, J.M., Kennedy, J. 2012. Diurnal temperature range compression hastens berry development and modifies flavonoid partitioning in grapes. American Journal of Enology and Viticulture. 63:112-120. Interpretive Summary: Various chemical components of wines are influenced heavily by growing conditions in the vineyard. However, we do not have complete knowledge of the environment-chemistry interactions in grapes. Therefore, we manipulated the temperature of grape clusters at different times during their development to determine how one large class of natural chemical compounds, the tannins, develop. The temperatures applied reflected a few of the potential temperature scenarios associated with global climate change models. By increasing night temperature and also decreasing day temperature (reducing the daily temperature swing), grape berries matured more quickly. Although temperatures were changed by more than 10 degrees, the production of tannins was not changed.
Technical Abstract: Temperatures during the day and night are known to influence grape berry metabolism and resulting composition. In this study, the flavonoid composition of field-grown Vitis vinifera L. cv. Merlot berries was investigated as a function of diurnal temperature range (DTR). The DTR was compressed by cooling berries during the day and heating them at night. Before véraison, there were minor differences in proanthocyanidin (PA) composition in the skins and seeds due to temperature treatments, most notably a decrease in gallate-esterification of seed flavan-3-ols with compressed DTR. Compressing the DTR significantly hastened berry development and the inception of véraison. Treatments imposed after véraison had minimal impact on skin and seed PAs; however, compressed DTRs favored the partitioning of anthocyanins and flavonols towards B-ring di-substitution. Compressing the DTR of grape berries had a consistent effect on berry development and partitioning of flavonoid metabolites while total flavonoid content was not significantly altered.