Effects of mechanical leaf injuring on metabolite composition of berries, and cluster and berry traits of different grape cultivars

Research; in the years 2021 and 2022, a total of 100 decares of vineyard owned by Te-Ha Consulting and Agriculture Ltd. Company located in Tekirdağ, at the coordinates 41° 01' 13.15" N latitude and 27° 28' 15.23" E longitude, and at an altitude of 235 m, where 17-year-old Cabernet-Sauvignon/SO4 and Merlot/SO4 grafting combination. The vineyard is set up with vine rows spaced 2.6 x 0.9 m apart, and the vines are trained using the double-armed Cordon Royat pruning system. The study investigated the effects of abiotic stress created on living vines on secondary and primary metabolites. Different abiotic stress conditions were induced by mechanical leaf injury at various times (15 days before harvest, 10 days before harvest, 5 days before harvest, 3 days before harvest, and 1 day before harvest), and changes in various phytochemical properties and phenolic compounds in the grapes were examined. Additionally, the effects of the two-year repeated mechanical leaf injury application on grape berry characteristics (width, length, weight, volume, etc.) and cluster characteristics (width, length, weight, volume, density, etc.) were determined. The results of the trial showed that the number of berries in the cluster and some cluster characteristics varied with the years due to climatic factors. Late-stage leaf injury applications resulted in an increase in berry characteristics. Among the phytochemical properties, sugar concentration (highest value of 224.91 g/L in HÖ5), sugar content in the grape berry (173.01 mg/g-berry in HÖ5), and total polyphenol index (10.00 in HÖ15-10) were affected by the applied treatments. Late-stage leaf injury (HÖ1 and HÖ5) applications led to an increase in phytochemical properties. In conclusion, under Tekirdağ conditions, late-stage leaf injury applications performed close to the harvest date, taking into account the climatic conditions of the year, were observed to result in increased yields for the Merlot and Cabernet-Sauvignon grape varieties.