Effects of Leaf Removal at Different Phenological Stages on Yield, Quality, and Growth of Karaerik Grapevines Trained in the Baran System

This study evaluated the effects of basal leaf removal at different phenological stages on yield, fruit quality, phytochemical composition, and winter bud physiology of the Karaerik grape cultivar under the Baran training system. Basal leaf removal was applied by removing five basal leaves at full flowering, pea-size berry, and veraison, and compared with an untreated control. The experiment was carried out over two consecutive growing seasons (2023 and 2024) using a randomized block design. The timing of leaf removal significantly influenced yield components and berry characteristics. Control vines produced the highest fresh grape yield (8.98 kg vine⁻¹), whereas vines defoliated at full flowering showed a moderate yield reduction (7.43 kg vine⁻¹). Despite this reduction, full flowering treatment substantially decreased cluster compactness (OIV-204: 4.58) compared with the control (7.58) and reduced the incidence of cracked and decayed berries by approximately 80%. Early defoliation also promoted berry growth, resulting in the highest single berry weight (5.91 g). Technological maturity parameters were positively affected by early leaf removal. The full flowering treatment resulted in the highest total soluble solids (19.07%), maturity index (27.42), and total phenolic content (504.57 mg L⁻¹). Moreover, leaf removal at full flowering and at pea-size berry significantly increased soluble carbohydrate concentrations in winter buds and reduced primary bud cold injury and necrosis. Overall, basal leaf removal at full flowering emerged as an effective vineyard management strategy to improve fruit quality, enhance phytochemical accumulation, and increase winter bud cold tolerance in Karaerik grapes cultivated under the Baran training system.