Preliminary Report on Effect of Level of Crop on Development of Color in Certain Red Wine Grapes

¹ Department of Viticulture and Enology University of California, Davis

Two levels of crop were obtained with mature vines of Alicante Bouschet, Carignane, Petite Sirah, Pinot Pernand, and Zinfandel by differential pruning or thinning in 1949, 1950, and 1951. With few exceptions more color developed in grapes on vines bearing a low crop. The maturation of fruit on vines bearing a high crop was usually delayed, as evidenced by a lower degree Balling and a higher retention of total acid on any given date.

The percentage of available carbohydrates (total sugars and starch) in the shoots was usually lower in the high-crop vines. Weight of pruning brush was usually greater in the vines bearing a low crop. Wines were made from the grapes, and those made from grapes from the low-crop vines usually scored highest.

There was considerable variation in these preliminary experiments, due to lack of replication of samples and the smallness of samples. Larger-scale experiments are now under way.