The function of source-sink relationships in grapevines on grape and wine production

Abstract

The production and storage of carbohydrates in grapevines is influenced by vineyard management and environmental conditions. The general pattern of seasonal perennial reserve utilisation is characterized by a decrease following bud-break, and then an increase that can begin any time between flowering and leaf-fall. Stored carbohydrate reserves support early shoot growth and the availability of reserves can influence reproductive development, including grape composition. The crop load impacts on grape maturation and carbohydrates allocated to the perennial structure, whereas the length of the period after harvest and its conditions, determine the replenishment of carbohydrate reserves for the following season. The availability of assimilates from leaves or reserves is crucial for berry sugar accumulation and metabolite production, ultimately reflected in must fermentation and the final wine. Further knowledge of carbohydrate dynamics and the influence of cultural practises on these source-sink relationships is critical to enhance grape and wine production. Several studies were conducted under warm climatic conditions to understand the source-sink relationships of grapevines, by investigating the seasonal carbohydrate dynamics, conducting experiments under controlled conditions and incorporating various vineyard management practices. In a major field experiment, crop load, canopy size, or water supply was altered on ‘Shiraz’ and ‘Chardonnay’ grapevines, affecting winter carbohydrate reserve status and fruit productivity. However, these practices did not substantially alter the seasonal pattern of reserve dynamics, suggesting that developmental stage or seasonal climatic factors have a stronger influence. In contrast, the impact of varying source-sink biomass significantly impacted on fruit composition, including sugar accumulation. These results were also reflected in the composition and sensory attributes of experimental wines, with influence on wine quality being more pronounced for ‘Shiraz’ than ‘Chardonnay’. Further detailed evaluations of carbohydrate dynamics during grape maturation are required to clarify the impact of management practises on vine carbon balance and implications for wine production.