Response of two French hybrid wine-grape cultivars to low light environments

The response of berry set, yield, and fruit quality characteristics to low light environments were examined for 'Seyval blanc' and 'De Chaunac' grapevines in the greenhouse. Potted vines of each cultivar with either 1 or 2 clusters were subjected to high or low light conditions, created by 80% shade cloth and supplemental lighting. 'Seyval blanc' had a higher percentage of mature berries per cluster, fewer shot berries, and a larger rachis diameter compared to 'De Chaunac'. Regardless of the cultivar or cluster number, clusters subjected to low light conditions had lower set, yields, cluster weights, berry weights, berries per clusters, and rachis diameters and had higher numbers of shot berries compared to clusters grown under high light conditions. Vines with one cluster matured a higher percentage of berries, possessed larger cluster weights and rachis diameters, and had lower yields than vines with two clusters. 'Seyval blanc' and 'De Chaunac' clusters grown under low light developed their golden and blue-red color more slowly than clusters grown under high light conditions. Overall, vines subjected to low light conditions produced clusters with lower soluble solids, pH, and potassium ion concentrations compared to vines grown under high light conditions. The soluble solids and pH of 'Seyval blanc' clusters were more sensitive to light than 'DeChaunac'. Titratable acidity levels and tartaric acid concentrations of 'Seyval blanc' were less sensitive to low light compared to 'De Chaunac' clusters.