A Study of the Variability of `Thompson Seedsess' Berries for Soluble Solids and Weight

Twenty-kilogram samples of `Thompson Seedless9 grapes were harvested on two dates from each of 7 vineyards in Fresno, Madera, and Yolo counties. Three hundred berries were clipped from each sample, ⅓ from the shoulder region of the clusters, ⅓ from the central region, and ⅓ from the tip. Each berry was weighed, after which °Brix was determined. Standard deviations and correlation coefficients were determined for °Brix, berry weight, and soluble solids weight per berry (calculated). Frequency distribution was analyzed by the chisquare test. Berry weight and soluble-solids weight per berry had normal distributions, whereas °Brix values usually did not. Berries from the tip region were lighter and of lower °Brix than berries from the other cluster regions. The regressions for °Brix and berry weight, regardless of vineyard location or cluster region, were curvilinear and of low order (R = 0.10 to 0.52).