Abstract
Higher temperatures caused by climate change are responsible for early maturation process which is often linked to low quality of grapes and wines. In this study, different canopy management techniques were tested and compared over three consecutive years (2017–19) with the aim to evaluate their capacity to delay ripening of Sauvignon blanc/SO4 grapes. These included a defoliation performed at veraison and the applications of antitranspirant (containing pinolene), kaolin and chitosan at bunch closure and veraison. The effects of the treatments on grapevine leaf gas exchanges, chlorophyll content and overall water status were measured during the three vegetative seasons. Moreover, soluble solids content and titratable acidity of berries were monitored from veraison until harvest, when final yield and berry composition were assessed. Pinolene transiently reduced the carbon assimilation rate and, independently from the growing season, significantly reduced sugar concentration in berries at harvest by -1.5°Brix as compared to the control. The defoliation reduced vine yield by 10–15 %, without significantly affecting total sugar and acid concentrations at harvest when compared to control. Kaolin and chitosan increased significantly berry acidity at harvest as compared to other treatments (i.e. defoliation and pinolene), but not to control. Under the temperate and rainy growing conditions of northeastern Italy, the antitranspirant product proved its potential as ripening retardant on a white grapevine cultivar. The high frequency of the rainfall events during the considered seasons partially hindered the full potential efficacy of the considered products sprayed to the canopy, questioning their overall efficacy under such conditions and mode of application.