Improving industry capacity to manage the yield and wine quality relationship through understanding the influence of vine carbon balance on berry composition

Summary

Objectives

To determine how vine balance influences berry ripening, secondary metabolite production and subsequent, wine quality. This will lead to new knowledge on the mechanistic effects of vine balance on fruit composition, and the methods and tools to allow this knowledge to be used in practice by grape growers and winemakers.

Background

Most growers rely on vine balance assessments from previous seasons and/or visual assessment of the canopy to determine if canopy manipulation is required. Previous experience is often used to determine the type and severity of canopy manipulation required, without clear understanding of how this influences vine physiology and wine quality.

Research approach

The project will investigate how pre- and post-veraison management practices determine the relationship between berry tannin, anthocyanin and sugar accumulation in berries and finished wine. Assessment of vine physiology, berry composition and final wine will be undertaken on field and pot-based experiments with a focus on Shiraz over three consecutive seasons. A range of field treatments are planned, including control, leaf removal prior to veraison, bunch removal prior to veraison, leaf removal prior to flowering and minimal pruning.

The pot-based, CO2 scrubbing treatment will reduce photosynthesis of vines (equivalent to increasing crop load) without needing to remove fruit or leaves and therefore without altering fruit exposure. This component aims to determine when berry ripening and metabolite production are most sensitive to changes in carbohydrate balance. The experimental design will help to understand how timing and severity of canopy manipulation influence fruit and wine quality.

Industry Benefit

Crop load and vine balance have been shown to strongly influence berry composition, but information on how to consistently achieve desired outcomes for sugar, acids, colour and tannins is lacking. This project will enable canopy and crop management techniques to be used more effectively in the management of berry composition and wine quality and will provide tools to assist in crop management decision making.