Effect of Applications of Gibberellic Acid on Berry Size, Shatter, and Texture of Thompson Seedless Grapes

Abstract

GA₃ was sprayed on Thompson Seedless vines at five different stages of berry growth and development from bloom to véraison. All vines were girdled at fruit-set (FS). The application of GA₃ [Bloom (B1) 15 ppm, FS 40 ppm] produced the smallest berries, and four sprays (B1 15 ppm, FS 40 ppm, two and four weeks after FS 40 ppm) resulted in the heaviest berries. GA₃ at véraison had little or no effect on berry size. The ratio of length to width of berries was also increased by three and four sprays of GA₃ with the ratio highest when four GA₃ were used. The GA₃ sprays after FS stage had no effect on the percentage shatter of berries, compared to controls. The °Brix was slightly less in the grapes which had received three or four repeat sprays of GA₃. GA₃ at véraison produced the hardest berries, as indicated by the force required for a probe to penetrate the flesh of these berries.