Impact of late pruning and elevated ambient temperature on Shiraz wine chemical and sensory attributes

Background and Aims: Viticultural practices are needed to counteract widespread, deleterious effects of warming on fruit and wine attributes. Late pruning is an effective tool to delay fruit ripening and improve berry and wine attributes, but the interaction between late pruning and elevated ambient temperature on wine chemical and sensory properties is unknown. We thus investigated the effect of delayed pruning, warming and their interaction in two contrasting seasons. 

Methods and Results: A factorial combination of three pruning times (winter pruning Control, and two late pruning treatments when Controls reached budburst or two–three leaves) and two thermal regimes (ambient temperature, heated) were established to investigate the interaction between pruning time and temperature on wine chemical composition and sensory traits during two seasons in Barossa Valley Shiraz. Average daily mean temperature at canopy level of the heated treatment was 0.40°C above Control in 2013/14, and 0.68°C in 2014/15. Sensory and chemical assessments showed reduced colour parameters in wines made from heated vines. Wines made from heated fruit were lighter in body and lacked palate length in comparison to unheated Controls. Wine colour density, concentration of anthocyanin and phenolic substances correlated negatively with daily mean temperature in a short window (2 weeks) immediately after veraison. 

Conclusion: Interactions between pruning and temperature treatments indicated that pruning at two–three leaves has the potential to partially mitigate heating effects by increasing wine colour and fruit flavour intensity in two contrasting seasons. 

Significance of the Study: Delayed pruning can help to partially counteract realised and projected warming effects, with neutral or positive effects for vine phenology, yield and wine properties.