Exogenous abscisic acid increases the anthocyanin concentration of berry and juice from 'Isabel' grapes (Vitis labrusca L.)

Abstract

Vitis labrusca grapes are widely cultivated in some countries such as Brazil and the United States, especially for juice production. 'Isabel' is one of the main cultivars because of its high production and disease tolerance, but the juice is deficient in color. The objective of this study was to evaluate the effect of timing and concentration of (S)-cisabscisic acid (S-ABA), a specific isomer of abscisic acid applied to 'Isabel' grapes, aiming to increase anthocyanin accumulation and to improve juice quality. The trial was conducted on two consecutive seasons (2011 and 2012) in a commercial vineyard located in Maringa, PR, Brazil. The vines were trained in an overhead trellis system and spaced at 4.0 × 1.0 m. The statistical model used was a randomized block design with four replications and five treatments: control; S-ABA at 200 mg·L-1 at 7 days after veraison (DAV); S-ABA at 400 mg·L-1 at 7 DAV; S-ABA at 200 mg·L-1 at 7 DAV + 200 mg·L-1 at 15 days after the first application (DAFA); and S-ABA at 400 mg·L-1 at 7DAV+ 400mg·L-1 at 15DAFA. There were no significant differences between treatments in relation to berry or cluster size or weight. S-ABA application resulted in increased anthocyanin concentrations in both berries and juices, mainly when 400 mg·L-1 was applied. Sensory analysis also revealed the efficiency of this plant growth regulator to promote better acceptance of grape juices. Thus, a single application of S-ABA at 400 mg·L-1 at 7 DAV is sufficient to increase the anthocyanins concentration of 'Isabel' grapes, improving the acceptance of juice by consumers.