EFFECT OF BUNCH SHADING ON COLOR AND QUALITY OF RED TABLE GRAPES (Vitis vinifera L.)

Abstract

Color is the most important external quality attribute in red grapes (Vitis vinifera L.). It is conferred by anthocyanins, which are highly influenced by environmental conditions. In this study we evaluated the effect of bunch shading on quality parameters and anthocyanins content in order to select the variables defining color development. Bunches of the cv. ‘Flame Seedless’ cultivated during the 2003-2004 growing season were used. They were covered in preveraisson with a white plastic net or a black net (assumedly both retained 50 % of luminosity) and a control treatment without shading. Significant shading effects were found on color parameters (hue, CIRG), but not on internal quality characteristics. Bunches covered with black net showed CIRG = 3.18 and accumulated 688 μg g^-1 of anthocyanins at harvest, which exceeded those of the control (CIRG = 3.10, 678 μg g^-1) and those bunches covered with white net (CIRG = 2.61, 653 μg g^-1). The correlations between color vs. total soluble solids, pH and titrable acidity were 0.69, 0.53 y -0.71, respectively. A logarithmic function (R²= 0.70) modeled the relationship between light intensity and bunch temperature. Minimum temperatures registered during the night defined color, described by a quadratic function (R²=0.86).