Overview
Open-top chambers warmed Barossa Valley grapevines by about 2 °C over two seasons. Warming advanced maturity less than long-term records suggested. It delayed anthocyanin accumulation relative to sugars in Shiraz and Cabernet Franc, which could disrupt colour–alcohol balance in red wines; water deficit before veraison partly restored this ratio. Warming raised juice pH in Cabernet Franc, Chardonnay and Semillon, and accelerated berry shrivel in Shiraz. Commercial records from three regions showed earlier maturity was driven mainly by earlier onset of ripening, so the report suggested practices to delay maturity should target onset. The common assumption of 1 °Bé per week biased harvest predictions in 8 of 9 cases, while locally calibrated ripening rates improved predictions.
This project belongs to Program 3 Grapes for Purpose, with a dominant element of Vine Performance and some elements of Berry Composition. The key strategy is “Collaborative investments in vine physiology” and the measure of success is “A better industry understanding of temperature, water and vine relationships”. Against this background, three major R&D needs had been identified:
(i) Scaling-up to the 3-way interaction between heat, water and variety.
(ii) Variety-dependent tools for in-season prediction of ripening for logistic purposes, i.e. harvest, transport and winery scheduling, and irrigation planning.
(iii) Viticultural practices to reduce heat damage.
This project had four objectives:
Enabling objectives:
1. To quantify the responses of Shiraz vines and wines to the combined effects of high temperature and water deficit under realistic vineyard conditions.
2. To quantify variety-dependent responses to high temperature and the interaction between temperature and fruit load per unit canopy size.
Practical objectives:
3. To develop user-friendly, robust models for variety-specific prediction of maturity. This will assist in harvest and winery scheduling, reduce costs, and help irrigation trusts in planning regional demand accounting for shifts in phenology and peak demand of irrigation water.
4. To develop management guidelines with emphasis on the interaction between heat stress, water supply and fruit load per unit canopy size.
Abstract
Temperature is one of the main environmental factors influencing vine physiology, berry composition and wine attributes. However, much of our understanding on the effects of temperature on vine physiology and berry composition has been gained from experiments under controlled conditions.
Categories
Climate adaptation
Viticulture
