Influence of Shoot Orientation on Growth and Yield Development in Cabernet Sauvignon

¹ Department of Viticulture and Enology, University of California, Davis, CA 95616-5270.

Beginning shortly after budbreak, 28 shoots from 14 mature field grown Cabernet Sauvignon vines at Davis, California, were trained to grow upward, horizontally, and downward. The plastochron index (PI) and leaf initiation rate (LIR) of each shoot were determined at four-day intervals until they reached a PI of 19. Cane pruning weight and time of budbreak were related to shoot growth rate and were thus used as covariates for testing the effects of growth direction. Downward-trained shoots generally exhibited reduced vigor as demonstrated by lower LIR and shoot extension rate, smaller primary leaves, fewer lateral leaves, and a lower cane dry weight density than did upward or horizontal shoots. The period from budbreak to bloom for downward-trained shoots averaged 2.3 days less than that for upward-trained shoots. At veraison, °Brix of fruits from upward-trained shoots was significantly higher than that for downward shoots. Percent fruitset did not differ between upward and downward shoots but was lower for horizontal shoots. The number of berries per shoot, however, did not differ among growth direction treatments.

Key words: Cabernet Sauvignon, shoot positioning

Submitted on March 10, 1989

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