Effects of Early-Season Leaf Removal on Shoot Development and the Physiology and Viability of Winter Buds in the Karaerik (Vitis vinifera L.) Grape Cultivar

Abstract

This study evaluated the effects of leaf removal applied at different phenological stages on phenological development, shoot characteristics, and the physiological status of winter buds in the Karaerik grape cultivar (Vitis vinifera L.). The experiment was conducted over three consecutive growing seasons (2019–2021). Leaf removal was applied at the pre-flowering (PF), full flowering (FF), and fruit set (FS) stages, while untreated vines served as the control. Based on three-year mean observations, leaf removal treatments tended to be associated with earlier phenological development compared with the control vines. Veraison occurred between July 28 and August 1 in the PF and FF treatments, whereas it was delayed until August 5–8 in the control vines. The budburst ratio was not significantly affected by the treatments and ranged from 89.25% to 90.74%. In contrast, the total number of inflorescences increased under leaf removal, reaching 27.44, 27.33, and 27.22 in the PF, FF, and FS treatments, respectively, compared to 26.22 in the control. Winter bud soluble carbohydrate content was significantly enhanced by leaf removal, with the highest concentration observed in the PF treatment (10.10 mg g-1), whereas the control vines exhibited markedly lower levels (4.87 mg g-1). Primary bud necrosis ranged from 3.00% to 4.11% in treated vines but increased to 9.11% in the control. The lowest cold injury rate was recorded in the FS treatment (4.67%), which also produced the highest bud fresh (3.05 g) and dry weights (2.10 g). Overall, leaf removal, particularly when applied at the pre-flowering and fruit set stages, was shown to be an effective cultural practice for advancing phenological development and improving the physiological quality and cold tolerance of winter buds in the Karaerik grape cultivar.