INFLUENCE OF LEAF REMOVAL, ROOTSTOCK, AND TRAINING SYSTEM ON YIELD AND FRUIT COMPOSITION OF PINOT-NOIR GRAPEVINES

A factorial designed experiment was used to vary leaf removal, rootsto ck, and training system of Pinot noir grapevines during two seasons. D efoliation consisted of 0, 2, 4, 6, 8, or 10 main leaves removed acrop etally from the shoot base six weeks after full bloom (pea-size). 3309 C and 101-14 Mgt were used as rootstocks, and the training systems use d were the traditional low-head, cane pruned system (double Guyot), wi th an undivided canopy, or a variant with a divided trunk structure ha ving a greater amount of two-year-old and older wood. Total yield and yield of sound fruit was reduced as leaf area decreased. Total yield w as higher on vines grafted to 101-14 Mgt, but so was the amount of dis eased fruit. Fruit yield showed a clear positive relationship with tru nk volume. Yield reduction due to defoliation or rootstock was mainly the result of reduced berry weight. Fruit composition was influenced b y defoliation and trunk volume; degrees-Brix and pH declined with incr easing level of leaf removal and increased with increasing trunk volum e. These data suggest that evaluation of training system choice should include the amount of two-year-old and older wood, since even small a mounts (<10% of total) resulted in significant impact on vine growth, yield components, and fruit composition.