Manipulation of ripening via antitranspirants in cv. Barbera (Vitis vinifera L.)

Background and Aims: Accelerated berry sugar accumulation resulting in wines of excessive alcohol concentration, sub-optimal colour and atypical flavour has become increasingly frequent in warm growing districts, a trend induced by factors that include global warming. The application of a film-forming antitranspirant may be an effective way of reducing early sugar accumulation without affecting colour development. Methods and Results: An antitranspirant emulsion was applied in 2013 and in 2014 on field-grown cv. Barbera vines at pre-flowering (PF), pre-veraison (PV) and at both dates (PFPV), and compared with the unsprayed control. Post-treatment assessment included seasonal gas exchange, yield components, growth of berry organs and must composition. Although all treatments were effective in reducing gas exchange by as much as 46% compared with that of the control, berry growth was not affected. Conversely, whereas PF slightly modified the ripening pattern, PV and PFPV markedly delayed accumulation of sugar in the warm 2013 season (-2.4 and -3.7 degrees Brix, respectively, vs control) without detriment to colour development because the onset of anthocyanins occurred at lower TSS. In the cooler, wet 2014 season, PV and PFPV were again able to delay sugar accumulation without affecting colour development. Conclusions: Pre-veraison application of the antitranspirant alone or in combination with a PF spray proved effective in slowing sugar accumulation while avoiding concurrent delay of colour development. Significance of the Study: The use of antitranspirants is a practical and flexible way of regulating the sugar : anthocyanin ratio under conditions of excessively fast ripening.