Effects of cluster thinnings on yield and quality parameters in Shiraz grape cultivar

Effects of cluster thinning which is applied after berry set on physical and chemical changings in berries and yield characteristics of grapevines were investigated. Cluster thinning were applied after berry set at 4 levels (8, 16, 24 and 32 cluster/vine) in Shiraz grapevines grown in Güney vicinity of Denizli. Application of 16 cluster per vine was accepted as control. Grape and cane yield per vine in addition to berry and cluster characteristic were recorded. Furthermore, total phenolics, total flavonoids and total monomeric anthocyanins were also measured as biochemical characteristics of berries. Antioxidant activity of grape berries were compared by using DPPH, TEAC and FRAP methods. Highest grape yield were obtained in the application of 32 cluster per vine (5576.70 g/vine). There are no statistically differences among cluster thinning applications in cluster weight, cluster length and cluster width. Values of berry weight, width and lengths were statistically different in all applications. Minimum berry weight (1.51 g) were recorded in the application of 32 cluster per vine while maximum numbers in control vines. Highest total phenol (285.20 mg GAE/100g) and total flavonoids (100.68 mg CTE/100g) were recorded in the application of 8 cluster per vine. Maximum monomeric anthocyanin (3.29 mg/g) was recorded in lowest crop load (8 cluster/vine). Antioxidant activities were recorded as 0.94 to 1.14 mg/ml in DPPH, and 10.02 to 14.85 ?M/g FW in TEAC and 1.14 to 1.29 ?M/100g in FRAP methods. Minimum values were recorded in highest crop load (32 cluster/vine) whereas maximum numbers in lower crop loads (8 and 16 clusters/vine).