Three clones of Malbec (Vitis vinifera L., syn. Cot) from Foundation Plant Services (FPS) were evaluated in Oakville, Napa Valley, California. Clones FPS 4, FPS 6, and FPS 8 were grown on two rootstocks, 110 Richter (110R) and Teleki 5C (5C). Vine yield components, fruit composition, and vegetative growth were measured over four growing seasons, 1997 through 2000. Shoot number per vine was held constant for all clones in a given year. Yield per vine, berries per cluster, cluster weight, clusters per shoot, and cluster number differed significantly among clones and between rootstocks. Berry weight differed significantly among clones, but not between rootstocks. All yield components varied significantly over the four vintages. FPS 8 had the highest yield and yield components, while FPS 6 had the lowest. Rootstock 110R had significantly higher yield than 5C by having more clusters and more berries per cluster. Yield component berries per cluster was most strongly correlated with yield differences. Pruning weight was inversely related to yield, where FPS 8 had the lowest pruning weight and FPS 6 the highest. The Ravaz index (yield to pruning weight ratio) was highest for FPS 8 and lowest for FPS 6. In years of greater yield, FPS 8 had greater soluble solids than FPS 4 or 6.
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