Déterminisme de l’effet terroir: influence de la surface foliaire primaire de la vigne en début de cycle sur le potentiel vendange

ln the Mid-Loire Valley, in France, for the fast twenty years a network of experimental plots has been used to analyse the terroir effect on the behaviour of the Cabernet franc variety of grape. The study of the primary leaf area (SFI) for several vintages shows that it differs greatly from one terroir to another. The SF1 can be characterized by the precocity of its setting in relation with bud-break earliness, and the effective area in place at flowering time. At this stage, differences between precocious and late terroirs can be more then 100%. The further evolution depends on the vigour originated by the terroir, which is main/y related to its water supply capacity. The type of evolution and the consequences on the composition of the berries can be appraised through the kinetics of the SF1 growth during the pre-flowering period. This analysis of a differentiation in the setting of the primary leaf area in relation with the terroir indicates that the construction of quality may begin very soon, at the early stages of the grapevine cycle. A model of physiological pathways of the ripening process is proposed, for the Northern vineyards. lt takes into account the importance of the “precocity” factor during the first part of the cycle, and the “water supply” during the second part.