Effects of Bloom-Applied Gibberellic Acid on Soluble Solids and Berry Weight of Thompson Seedless Grapes and on Raisin Grades

Abstract

The distributions of Thompson Seedless berries for weight and soluble solids weight were normal whether or not the vines were sprayed during bloom with gibberellic acid (GA₃) at concentrations of 5 or 10 ppm. The distributions for soluble solids content, however, mostly departed significantly from normality.

Airstream grades of raisins, either as percent B or better, or percent substandard, correlated significantly with fruit maturity (°Brix) and fresh berry weight, similarly to raisins from nongibberellic acid-treated vines.

Bloom-applied GA₃ at 10 ppm significantly increased fresh berry weight, but not maturity, vine yield, or percent water berries. Neither were raisin berry weight, airstream grades, or scoreable mold levels significantly affected by GA₃ at either 5 or 10 ppm.