PT  - JOURNAL ARTICLE
AU  - Jean Riesterer-Loper
AU  - Beth Ann Workmaster
AU  - Amaya Atucha
TI  - Impact of Fruit Zone Sunlight Exposure on Ripening Profiles of Cold Climate Interspecific Hybrid Winegrapes
AID  - 10.5344/ajev.2019.18080
DP  - 2019 Mar 19
TA  - American Journal of Enology and Viticulture
PG  - ajev.2019.18080
4099  - http://www.ajevonline.org/content/early/2019/03/14/ajev.2019.18080.short
4100  - http://www.ajevonline.org/content/early/2019/03/14/ajev.2019.18080.full
AB  - The introduction of cold climate interspecific hybrid grape (CCIHG) cultivars has propelled a new wine industry in northern climates; however, the high fruit acidity levels at harvest and the limited information on the fruit composition of these new cultivars are a challenge for the production of quality wines. In the present study, organic acid and sugar profiles were determined during two growing seasons for Brianna, Frontenac, La Crescent, and Marquette under control and fruit zone exposure (“exposed”) treatments consisting of the removal of 2-3 leaves per shoot that were shading clusters, as well as lateral shoots from the first three node positions, two weeks after fruit set. From veraison to harvest, glucose to fructose ratios ranged from 0.88 to 1.13, and tartaric to malic acid ratios ranged from 0.23 and 0.88 between years and cultivars. La Crescent and Frontenac had higher levels of acidity from veraison to harvest, mainly due to high levels of malic acid. The exposed treatment increased irradiance in the cluster zone, as well as berry temperature. Treatment effect on fruit glucose and fructose concentrations varied among cultivars and growing seasons. The exposed treatment reduced total titratable acidity, particularly malic acid concentrations, compared to the control for almost all cultivars evaluated. Leaf and lateral shoot removal just prior to veraison could be an effective tool to reduce acidity in CCIHG grown in cold climate regions with short growing seasons. In addition, this work highlights the need for the development of independent fruit maturity standards for CCIHG, as opposed to relying on those established for Vitis vinifera cultivars.