‘Riesling’ Grapes Respond to Cluster Thinning and Shoot Density Manipulation

Five-year-old ‘Riesling’ grape ( Vitis vinifera ) vines growing in the Okanagan Valley of British Columbia were subjected to three crop levels (full crop, two clusters per shoot, and one cluster per shoot) in combination with no shoot thinning or thinning to 24 shoots per meter of row. Reduction in crop level improved vine size and cane periderm formation slightly. Yield per vine was linearly related to crop level, but berry weight, berries per cluster, and cluster weight increased with decreasing crop level. °Brix and pH increased and titratable acidity decreased with reduction in crop level. Thinning to 24 shoots per meter of row provided some improvement in yield components and °Brix. Crop loads below 10 kg of fruit per kilogram of cane prunings are necessary to achieve adequate fruit maturity under Okanagan conditions.