Quality of phenolic compounds of cv. Primitivo as a function of the defoliation and the application of abscisic acid

Abstract

Green pruning provides better conditions to the vegetative canopy of the vine, favoring aeration and insolation in the region of the bunches, providing better conditions for its maturation. The use of plant regulators, such as abscisic acid (ABA), has also been studied to increase the concentrations of phenolic compounds in the berry peel of the treated grapes, improving their coloration. With the objective of verifying the effect of defoliation and the application of abscisic acid on flavonoid content, an experiment was conducted in a commercial vineyard with cv. Primitivo (Vitis vinifera) in Água Doce, Santa Catarina, Brazil, during two consecutive seasons (2015/2016 and 2016/2017). The experimental design was randomized blocks with 6 treatments and 4 replications, in the crop. The treatments were as follows: control; defoliation at the beginning of maturation (DIM); defoliation 21 days before harvest (D21); ABA 200 mg L^-1 (ABA 20); ABA 400 mg L^-1 (ABA40); ABA 600 mg L^-1 (ABA60). The following evaluations were performed: soluble solids (°Brix), titratable acidity (% tartaric acid), pH and flavonoid content (mg 100g^-1). The chemical characteristics were not influenced by the treatments, except for the first season, when treatment with ABA40 had the highest titratable acidity. For the flavonoid content, in the first season, treatment with ABA20 obtained the highest value (71,8 mg 100g^-1), but did not differ from the control (70,5 mg 100g^-1). In the second season, ABA40 and ABA60 significantly increased the flavonoid content between 130 and 133% relative to the control. This increase in the concentration of flavonoids promotes improvement in the coloring of the berries.