Abstract
A new method of Gibberellin (GA3) treatment was developed to avoid GA-induced hardening of the rachis in ‘Pione’ grapes (Vitis vinifera L.×Vitis labrusca L.).
GA solution including starch or gelatin, to increase its viscosity, was spread on the surfaces of clusters using the palm of the human hand. The solution with starch contained 39ppm GA (treatment at bloom) and 78ppm GA (postbloom treatment). The solution with foamed gelatin contained 139ppm GA (treatment at bloom) and 156ppm GA (postbloom treatment). The effects on berries of this GA treatment (spreading) were compared with conventional GA dipping and with untreated specimens.
GA spreading settled more berries on the clusters than GA dipping. The size, color, seedless rate, Brix and acid in mature berries treated by GA spreading were all similar to values for GA dipping.
Rachises of berries treated by GA spreading were as slender and as flexible as those of untreated berries, and were similar in length to those treated by GA dipping. GA spreading could prevent the hardening of the rachis, but not the postharvest dropping of berries. The postharvest dropping of berries treated with GA could be caused by weak berry adhesion rather than by the hardness of the rachis.
