Grapevine Berry Growth and Sugar Loading During Ripening Are Differentially Impacted by Environment X Management Interactions

Abstract

Background and Aims: Grapevine berry ripening is driven by water and sugar loading from the phloem, beginning with berry softening and ending at physiological maturity. This study aimed to characterise the kinetics of sugar and water accumulation at the berry population level under different climatic, vigour and crop management conditions. Methods and Results: The experiments were conducted in a commercial vineyard of the ‘Tannat’ cultivar in Uruguay, for 8 years. Two zones with high (H) and low (L) vigour were delimited. In two contrasted rainy and dry years, specific treatments (nitrogen, water availability and leaf/fruit ratio) were carried out. The sugar and water accumulation kinetics were studied on populations of berries, which were both synchronised from the onset of ripening to maximum sugar loading and normalised by their maximum volume. A bilinear model between berry growth and sugar accumulation was fitted, indicating an apparent uncoupling between water and sugar loading. Wet and high-vigour conditions accentuated this apparent uncoupling compared to dry and low-vigour conditions, with maximum berry growth reached earlier than the maximum sugar content. In addition, management practices favouring plant water and carbon status positively influenced the duration of ripening (up or down). Conclusions and Significance: This study provides a deeper understanding of how management practices can be harnessed to improve grape production. Water management was a key lever to counteract the climatic and/or vigour impact both on the apparent uncoupling between berry growth and sugar loading at the population level and the asynchrony of berry development within the population.