Vine water status and aroma potential: the behavior of Shiraz and Grenache N. in the Mediterranean area

Abstract

The scenarios on the climate changes seem to predict an increase of the water deficit in the Mediterranean area during the grape maturation period, both in frequency and in magnitude. If the effects of water constraint on the vine vegetative development and the berry composition (sugars, acidity, minerals, phenolics) is reported in literature, very few data are available for the aromatic potential. Thus, during a PhD thesis, we studied the impact of the vine water status on 3 components of the aromatic potential of both Shiraz and Grenache Noir, two varieties widly planted in the Mediterranean area. Rotundone, aroma glyconjugates and the dimethylsulfide potential (PDMS) were considered in this study, but in our conditions no signicant levels of rotundone could be analyzed. In contrast, the plots monitored during three vintages (2011-2013) yielded results which demonstrated a different behavior between these two varieties for aroma glycoconjugates and PDMS. Aroma glycoconjugate levels in berries were slightly influenced by the water status of Grenache Noir except when natural defoliation occurred, that induced a higher C₁₃-norisoprénoïde, terpenol, and phenol glycoconjugate accumulation in berries, likely due to the increase in sun exposure of the bunches. On the contrary, a higher glycoconjugate accumulation was observed in Shiraz berries under water deficit conditions. The PDMS levels in Grenache Noir berries were correlated with amino acid levels, and positively influenced by water deficit. Maturity state had a smaller influence. For Shiraz, this correlation was not observed but a water deficit, particularly on post veraison period, induced higher PDMS levels. The anisohydric behavior of Shiraz variety could be related to those PDMS levels.