Atypical ageing and hydric stress: insights on an exceptionally dry year

Atypical ageing (ATA) is a white wine fault characterized by the appearance of notes of wet rag, acacia blossoms and naphthalene, along with the vanishing of varietal aromas. 2-aminoacetophenone (AAP) – a degradation compound of indole-3-acetic acid (IAA) – is regarded as the main sensorial and chemical marker responsible for this defect. About to the origin of ATA, a stress reaction occurring in the vineyard has been looked as the leading cause of this defect. Viticultural, climatic and pedological factors are the main triggers and among them, drought stress seems to play a crucial role. [1] Available water capacity (AWC) is defined as the amount of water a soil can store that is available for use by plants. This index might be employed to gauge a predisposition to hydric stress which could ultimately lead to the onset of ATA. Considering previous research which has demonstrated that ATA development is likely to occur in fields having 30-40 mm AWC [2] , this relationship was further investigated in the present study in an exceptionally dry year such as 2022. 11 fields located in Trento (Italy) were grouped according to their AWC (low, medium, high) and closely monitored over the course of the harvest season. Given the climate conditions of the year, all of the fields under examination were subjected to drought. While grapevines belonging to the ‘low’ class experienced severe stress conditions (midday leaf water potential, Ψleaf>15 bar), the ‘medium’ and ‘high’ classes were only moderately stressed (15>Ψleaf>12). Accordingly, all wines obtained were affected by ATA, displaying concentrations of AAP above the odour threshold (0.5 μg/L). Nonetheless, the AAP content of the ‘low’ class was significantly higher than the other classes. It was concluded that in exceptionally dry years, grapevines planted on fields characterised by a low AWC are more subjected to produce faulty wines characterised by ATA.