Girdling timing effect on maturation hastening of ‘Rubi’ table grape

Abstract

This research was an attempt to evaluate the girdling timing effect to hasten the maturation of table grapes produced out of season in the northwest of Parana State, Brazil. The experiment was carried out in a commercial vineyard of ‘Rubi’, Vitis vinifera L. (Vitaceae) and the following treatmentes were evaluated: a. control; b. girdling 3 weeks after full bloom; c. girdling at the beginning of ripening (véraison) and; d. double girdling (treatments b and c). Girdling consisted of removing a narrow ring of bark entirely round of the trunk using a double-bladed 3.1 mm knife, at 1.5 m from the ground. A randomized block design with four treatments and four replications was used as a statistical model. Each plot was composed by one plant. Total soluble solids (TSS) and titratable acidity (TTA) were evaluated weekly through berries samples collection, from the establishment of the experiment up to its harvesting, totalizing eight samplings. During harvesting, some clusters characteristics as weight and length and berry size were also analyzed. Both TSS and TTA presented linear correlation as function of time for all treatments and through linear regression, it was estimated the period to the clusters reached the maturation, considering 14 oBrix as standard. The treatments b and c showed the highest periods of maturation hastening in relation to the control (13 and 5 days, respectively). There was no difference in relation to the ATT decrease pattern in berries not even to the clusters characteristics among treatments