Interactions of summer pruning techniques and vine performance in the white Vitis vinifera cv. Ortrugo

The increasing interest by the wine market in sparkling white wines challenges how the desired grape composition can be achieved under the pressure of global warming. The aim of the present study was to assess the viability of summer pruning as a tool to pilot ripening towards desired compositional patterns. Methods and Results: Ortrugo was subjected to basal leaf removal applied either at pre-flowering (ELR) or in lag-phase (LLR) and to bunch thinning (BT; removal of 50% of crop at lag-phase) in comparison with untreated control (C). Treatments induced large variation in bunch mass (30% less in ELR vs BT), yield per vine (37 and 21% less in BT and ELR vs C) and total soluble solids at harvest (BT scored 2.9°Brix higher than that of C). Conversely, given the same harvest date, all practices failed to maintain titratable acidity (TA) at the threshold of 6.5g/L. Conclusions: The data suggest that crop regulation achieved in the high yielding Ortrugo, through either BT or ELR, increases sugar accumulation rate so that concurrent optimal TA level (≅6.5g/L) can be easily achieved by slightly anticipating harvest date. Under conditions of thermal or light stress, or weather conducive to bunch rot, preference should be given to ELR. Significance of the Study: Suitable summer pruning techniques might be used as flexible and powerful tools to direct ripening towards the desired crop composition.