Effects of Leaf Removal Application in Different Phenological Stages on Yield and Quality Parameters in Karaerik Grape Variety

This two-year study evaluated the effects of basal leaf removal applied at five phenological stages (pre-flowering, full flowering, fruit set, pea-size berry, and veraison) on yield, cluster structure, berry morphology, and chemical composition of the ‘Karaerik’ grape cultivar under the ecological conditions of Erzincan. The study aimed to determine the optimal timing of leaf removal as a cultural practice to improve quality in large-berried, compact-cluster table grapes. Leaf removal treatments were applied at the specified growth stages, and yield per vine, cluster characteristics, berry traits, cracking incidence, and chemical and phenolic properties were assessed over two consecutive seasons. The results indicated that leaf removal significantly affected both yield and quality parameters. Yield per vine decreased compared with the control, particularly when leaf removal was performed at the flowering stage, where yield declined from 11.93 kg vine⁻¹ to 9.70 kg vine⁻¹. In contrast, several morphological traits improved following leaf removal. Berry weight increased from 4.69 g in the control to 5.72 g with pre-flowering applications, accompanied by increases in berry size and reductions in cluster compactness. All leaf removal treatments reduced the number of cracked berries relative to the control. Chemical composition was also influenced by treatment timing. Total soluble solids increased from 17.05 °Brix in the control to 18.64 °Brix with leaf removal at full flowering, while titratable acidity decreased and the maturity index increased. In addition, early and mid-season leaf removal enhanced bioactive compounds, with the highest total phenolic (508.70 mg L⁻¹ GAE) and total flavonoid (102.90 mg g⁻¹ CE) contents recorded at the fruit set stage. In conclusion, leaf removal was an effective practice for improving grape quality; however, its effects strongly depended on phenological timing. Applications at flowering reduced yield, whereas treatments at fruit set and pea-size berry stages provided a more favorable balance between yield and quality in ‘Karaerik’ grapes.