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, rootstock, and training system of Pinot noir grapevines during two seasons. Defoliation consisted of 0, 2, 4, 6, 8, or 10 main leaves removed acropetally from the shoot base six weeks after full bloom (pea-size). 3309C and 101-14 Mgt were used as rootstocks, and the training systems used were the traditional low-head, cane pruned system (double Guyot), with an undivided canopy, or a variant with a divided trunk structure having 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 was higher on vines grafted to 101-14 Mgt, but so was the amount of diseased fruit. Fruit yield showed a clear positive relationship with trunk volume. Yield reduction due to defoliation or rootstock was mainly the result of reduced berry weight. Fruit composition was influenced by defoliation and trunk volume; degrees-Brix and pH declined with increasing level of leaf removal and increased with increasing trunk volume. These data suggest that evaluation of training system choice should include the amount of two-year-old and older wood, since even small amounts (<10% of total) resulted in significant impact on vine growth, yield components, and fruit composition.