Prohexadione-calcium is a gibberellin biosynthesis inhibitor used to suppress the vegetative growth. The objective of this work was to evaluate the effect of prohexadione-calcium on vigor reduction, productivity and quality of Grano d'Oro, a mutation of Bordô (Vitis labrusca L.) grapevine. Apogee® was used at a concentration of 250 mg L-1 of Prohexadione-calcium in different spray dates. The treatments were applied at full bloom, 45 days after full bloom and a control (no application). The experimental design was a completely randomized blocks design, with four blocks and 20 plants per plot. Marked branches were measured to assess the growth curve. During harvest, the bunch number per plant, productivity (kg plant-1 and T ha-1), 50 berries weight, berry number per cluster, total soluble solids (°Brix), total acidity (meq L-1) and pH were determined. Prohexadione-calcium application at full bloom reduced branch growth in 33% at the 15th day after full bloom, this reduction decreased over the cycle, and at the 93th day after full bloom reached 8%, compared to the other treatments. Prohexadione-calcium application at full bloom caused the higher vigor reduction and the higher productivity increase in Grano d'Oro grapevines. The productivity increase and the vigor reduction ran parallel to a total soluble solids reduction. The vigor reduction did not eliminate the need for shoot topping.
Vitis labrusca L; vegetative growth; Apogee®; plant growth regulator
