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

Vine balance is a concept describing the relationship between whole vine carbon uptake and its utilisation, as sugar, for fruit production. It is commonly considered that composition of the berry, and resulting wine, is strongly affected by vine balance. Field manipulations of vine balance were replicated, in three contrasting regions, for three seasons. In addition, the effect of defoliation was simulated, without changing bunch environment, by enclosing whole vines in chambers and supplying them with low CO2 air to reduce photosynthesis.
Changing vine balance consistently altered the rate of ripening, but did not correlate with treatment effects on fruit composition, where they occurred. Late defoliation extended the maturation period, but reduced total anthocyanin content. Crop removal shortened the maturation period, but had little effect on the fruit. Interestingly, early defoliation had no clear effect on vine balance, but resulted in both increased anthocyanin and increased tannin content. The chamber experiment also extended the maturation period, but had no effect on the relationship between sugar
and anthocyanins. Overall, there was no conclusive evidence that the changes in vine balance achieved had any significant effect on fruit or wine
composition when fruit were harvested at the same sugar ripeness.