The effects of cluster and berry thinning with leaf removal time on yield and quality of some wine grapes

Objective: To determine of the effects of leaf removal and berry thinning at pre-flowering and fruit set times with cluster thinning at verasion on yield and quality of Syrah (Vitis vinifera L.) and Sauvignon Blanc (Vitis vinifera L.) wine grapes. Material and Methods: The experiment was planned as completely randomized block design in split plots with three replications. While main plots formed leaf removals (LR), subplots occurred thinning applications (TA). TA were consisted of berry thinning (BT) at pre-flowering (PFBT) and fruit set (FSBT) and cluster thinning (CT) at verasion. Leaf removal levels were control (CONT), preflowering leaf removal (PFLR) and fruit set leaf removal (FSLR). From basal to fifth node, all leaves and second shoots were removed in Syrah. From basal to fifth node, less leaves and shoots were taken from west side of vines in order to protect excessive sunlight in Sauvignon Blanc. CT were applied respectively as 20 and 30 clusters/vine for Syrah and Sauvignon. BT applied at 1/3 ratios with cutting of cluster tipping or cluster wings in pre-flowering and fruit set. In harvest, berry and cluster samples were taken and made physical and biochemical analysis. Results: In Sauvignon Blanc, yield differences between years occurred. In high yield year, CT decreased yield as 15.2%. PFBT and FSBT decreased yield respectively as 16.7% and 9.7%. PFLR and FSLR resulted in less yield decreases respectively as 7.5% and 5.4%. While TA and LR increased total soluble solids (TSS), they did not change acidity, pruning weight, bud fertility, total phenolics and total phlovanoids. In Syrah, CT decreased yield as 24.0%. PFBT and FSBT decreased yield respectively as 6.5% and 9.4%. PFLR and FSLR caused yield decreases respectively as 11.1% and 8.2%. While CT increased TSS, LR did not affect TSS. Neither TA nor LR made difference on acidity, pruning weight, bud fertility, antioxidant capacity, total phenolics and total phlovanoids. Conclusion: For Sauvignon Blanc, FSBT is suggested when compared CT because FSBT caused less yield decreasing and not changing of TSS and berry skin color. In addition, PFLR an FSLR also suggested in order to less yield decreases and not changing of TSS and bud fertility when compared with CT. For Syrah, when compared with CT, FSBT is suggested as alternative because of less yield decreasing and not making differences on TSS and cluster compactness. In a similar way, when compared with CT, although LR resulted in less yield decreases, LR did not increased TSS