Factors affecting berry composition of Tempranillo grapevines before the arrest of phloem transport

Abstract

It is already known that berry ripening is determined by the leaf area/fruit ratio, as well as temperature and leaf physiology. The aim of this work was to assess the influence of these parameters on Tempranillo cultivar throughout stage III of berry development. More specifically, the study was focused on the phase preceding the arrest of phloem transport, when the increases in berry weight and sugar accumulation are significant. The sugar concentration, titratable acidity, pH, and total phenolic content of the berries were quantified. Leaf area, canopy surface area, yield, cumulative growing degree days (GDD), leaf water potential, and stomatal conductance were measured during stage III of berry development. The relationship between berry composition parameters and agronomic indexes was determined by multiple regression analysis. The study was done from 2005 to 2008 in two Tempranillo vineyards, vertically shoot positioned, under regulated deficit irrigation, in which several alley widths, canopy heights and shoot densities were set. Concentrations of sugars and phenols were best estimated when surface area/yield, GDD and stomatal conductance, measured between veraison and maturity, were taken into account jointly. For titratable acidity and pH estimations, the use of surface area/yield, GDD and leaf water potential was found to be the best approach. Moreover, as grape acidity is conditioned by stage I of berry development, it was also necessary to include the GDD values from berry set to veraison for the study of titratable acidity and pH. These results point out that it is of great importance to take into consideration at least one indicator of vine balance, annual climate variation, and also physiological activity when estimating grape maturity. The monitoring of these parameters is already widespread among commercial vineyards, and a joint study of them would allow adapting cultural practices to yearly variations in climate in order to meet set production objectives.