Gibberellic acid and trunk girdling effect on ‘rubi’ table grape clusters

Abstract

This research was an attempt to compare the gibberellic acid and trunk girdling effect on some clusters characteristics of table grapes in the northwest of Parana State, Brazil. The trial was carried out in a commercial vineyard of a 5-year-old ‘Rubi’ (Vitis vinifera L.). A randomized block design with 5 treatments and 5 replications was used as a statistical model. Each plot was composed by 6 clusters. For gibberellic acid application, the commercial product ProGibb®, containing 10% of the plant regulator, was used. The following treatments were evaluated (dosis of active ingredient): Control (without application); b. 1,5 g/100 L; c. 3,0 g/100 L; d. 6,0 g/100 L and; e. Girdling. All treatments were applied 30 days after bloom. For treatments b, c and d, the plant regulator was applied on clusters using a manual sprayer until run-off, adding no spread sticker. Girdling (treatment e) consisted of removing a narrow ring of bark entirely round of the trunk using a double-bladed 3.1 mm knife, 1.5 m far from the ground. During the harvesting, the following production characteristics were evaluated: weight and size of clusters and; weight, width and total soluble solids of berries (TSS) (oBrix). It was not observed differences between treatments in relation to the weight and size of clusters, however, for weight and width of berries, the best results were observed for treatments c e e (dose 3,0 g/100 L and girdling, respectively). Girdling also provided higher TSS in relation to other treatments.