Bunch sizing of ‘BRS Nubia’ table grape by inflorescence management, shoot tipping and berry thinning

Abstract

Abstract ‘BRS Nubia’ is a new seeded table grape with dark black color, high yield, neutral flavor, and crunchy large berries. However, this cultivar frequently presents very dense bunches, limiting its commercialization. The aim of this work was to obtain uniform and loose bunches of ‘BRS Nubia’ table grape by means of inflorescence and bearing shoot management associated to berry thinning. The trial was conducted during two consecutive seasons of 2015 and 2016, in a 2-year old commercial vineyard located in Marialva, Parana, Brazil. The vines were trained in an overhead trellis system and spaced at 2.5 × 9.0 m distance. The experimental design was randomized block with four replications in a 2-factor arrangement with two additional treatments (factorial 2 × 2 + 2). The following factors were evaluated: inflorescence management (with tipping before anthesis and without tipping), bearing shoot tipping (before or after anthesis), and two additional treatments consisted of two controls (with or without berry thinning). The berry thinning was performed in all treatments, except in control without berry thinning, by means of picking when berries were at pea size. Physico-chemical analysis of the berries as well as bunch compactness and yield were evaluated at harvest time. Means were subjected to analysis of variance and compared using Tukey’s test at 5% probability. Additionally, the Principal Components Analysis (PCA) was used to describe the relation of physico-chemical and productive characteristics of grapes with the inflorescence and shoot management. The inflorescence tipping before anthesis is a useful practice by facilitating and saving time to perform berry thinning of ‘BRS Nubia’ table grapes, while the bearing shoot tipping after the anthesis may accelerate the bunches ripening. Combined to these practices, berry thinning is a mandatory procedure in order to obtain medium loose bunches of ‘BRS Nubia’ table grape, with larger and uniform berries.