Eugenol:  a new marker of hybrid vines? The case study of Baco Blanc in Armagnac

Sulfonated monomeric and dimeric flavan-3-ols are recently discovered in wine and proved to have great importance in understanding wine chemistry and quality [1, 2].

The Champagne vineyard extends over 35,300 ha under the Appellation d’Origine Contrôlée, of which 30,000 are in production. It mainly covers 3 departments: in order of importance, Marne (68% of the appellation area), Aube (22%) and Aisne (10%), and more anecdotally Haute Marne and Seine and Mame. It is a young vineyard (for more than half of the surface, the winegrowers have the experience of only one generation of vines), and fragmented (more than half of the exploitations extend over less than 1 ha; the average size of a cadastral parcel is 12 ares).

Plant water status of grapevine plays a critical role in affecting berry and final wine chemical composition. The environmental variabilities existing in vineyard system have significant impacts on plant water status, but it is challenging to individualize environmental factors from the temporal and spatial variabilities in vineyard. Therefore, there is need to monitor the ecophysical variation through utilizing precision viticulture tools in order to minimize the separation in berry composition. This study aims at delineating vineyard into different management zones based on plant water status explained by soil texture, and utilize differential harvest to equilibrate the final berry and wine composition.

The current climate changes are directly threatening the balance of the vineyard at harvest time. The maturation period of the grapes is shifted to the middle of the summer, at a time when radiation and air temperature are at their maximum. In this context, the implementation of corrective practices becomes problematic. Unfortunately, our knowledge of the climate effect on the quality of different grape varieties remains very incomplete to guide these choices. During the Innovine project, original experiments were carried out on Syrah to study the combined effects of normal or high air temperature and varying degrees of exposure of the berries to the sun. Berries subjected to these different conditions were sampled and analyzed throughout the maturation period. Several quality characteristics were determined, including anthocyanin content. The objective of the experiments was to investigate which climatic determinants were most important for anthocyanin accumulation in the berries. Temperature and irradiance data, observed over time with a very thin discretization step, are called functional data in statistics. We developed the procedure SpiceFP (Sparse and Structured Procedure to Identify Combined Effects of Functional Predictors) to explain the variations of a scalar response variable (a grape berry quality variable for example) by two or three functional predictors (as temperature and irradiance) in a context of joint influence of these predictors. Particular attention was paid to the interpretability of the results. Analysis of the data using SpiceFP identified a negative impact of morning combinations of low irradiance (lower than about 100 μmol m−2 s−1 or 45 μmol m−2 s−1 depending on the advanced-delayed state of the berries) and high temperature (higher than 25oC). A slight difference associated with overnight temperature occurred between these effects identified in the morning.

L’observation est effectuée entre 1996 et 1998. L’expérience a commencé avec des clones numérotés: 75, 95, 96 et 227 de la variété Chardonnay. Le porte greffe est le Kober 5 BB. La forme de conduite est le cordon. La taille est longue. La densité de plantation est 3,5 x 1 mètre (2857 ceps par 1/ha).