Control of the initiation and progression of ripening can alleviate problems associated with increasingly narrow harvest windows and undesirable shifts in the timing of the ripening phase. The aim of this project is to further develop, optimise and commercialise the use of pre-veraison plant growth regulator (PGR) applications to control ripening (thereby expanding the harvest window) and improve berry quality. Ripening-delaying treatments using auxins such as NAA (1-naphthaleneacetic acid) and other PGRs will be fined tuned and treatments adapted to a commercial setting. The project will further investigate the effect of ripening-delaying treatments on fruit quality parameters, focusing on a selection of flavour/aroma compounds and on the improvement of ripening synchronicity between berries/bunches. Developing mass spectrometry-based methods for the analysis of non-volatile grape metabolites will allow the classification of pre-veraison grapes into defined developmental stages and identify those stages most responsive to PGR treatments. These methods will allow vineyard managers to reliably predict the best time to treat the fruit for optimal effect on ripening.