Hormonal Control of Grape Berry Ripening

Grape berry ripening, like many other developmental processes, clearly involves the coordination of a large number of events. Some metabolic activities that occur prior to véraison, such as photosynthesis and organic acid accumulation, are either turned off at véraison or are at least down regulated. Other processes, such as the accumulation of anthocyanins in berry skins, commence at véraison. In this chapter we will use the last time-point before an accumulation of sugars is recorded as the working definition of véraison. Where possible the data from papers has been reinterpreted to align with this definition. The changes that occur as the berry begins to ripen have received considerable attention at the physical and biochemical level (Ollat et al. 2002, Conde et al. 2007), but their overall control and coordination remains poorly understood. Not only are the timing and extent of changes in the berry coordinated but this control has to extend over a range of diverse primary and secondary metabolic pathways. In addition, many of the ‘subprograms’ that make up the greater ripening ‘program’, such as colour and sugar accumulation, are responsive to environmental conditions which influence their progress. The control system that initiates and maintains the ripening phase must therefore be complex, able to coordinate diverse portions of metabolism and must be to some extent flexible.