Applied GA(5), GA(4), and GA(4/7) increase berry number per bunch, yield, and grape quality for winemaking in Vitis vinifera L. cv. Malbec

BACKGROUND The gibberellins (GAs) GA(5) (inhibitor of GA(3)-oxidase), GA(4) (biologically active), GA(4/7) (commercially available mixture of Ga-4 and GA(7)) prohexadione-calcium (ProCa, inhibitor of dioxygenases that render GAs bioactive, negative control), and GA(3) (positive control) were applied to bunches of Vitis vinifera cv. Malbec. Different techniques, doses, and timings were used in a 3-year field experiment. In year 1, GA(5), ProCa, and GA(3) were applied at 35, 20, and 0 days before veraison (DBV) by dipping bunches three times. In year 2, single applications of GA(5) and GA(3), also by immersion, were tested at 60, 45, and 30 DBV. In year 3, applications at 60 and 30 DBV of GA(5), GA(4), and a mixture of GA(4/7) were evaluated by dipping or spraying the bunches. RESULTS Vegetative growth, berry weight, and sugar content were unaffected by treatments. ProCa did not affect the yield with respect to water control, although it reduced the levels of phenolics in berry skins, an undesirable effect for winemaking. GA(5), in the dose range 5-50 mg L-1, raised berry numbers, thereby augmenting bunch weight and skin phenolics at harvest, so increasing berry quality for winemaking. GA(4) and GA(4/7) produced similar benefits to GA(5), with similar doses. CONCLUSION The applications of GA(5), GA(4), and GA(4/7) to developing grape berry bunches, in a range of concentrations and by dipping or spraying, increased berry numbers per bunch at harvest. The method can be used as a viticultural practice to improve the production and quality of wine grapes. (c) 2021 Society of Chemical Industry.