Performance of cv. Cornalin under pedoclimatic conditions of the Valais region (CH)

The experiment carried out between 2005 and 2010 in 24 plots of Vitis vinifera cv. Cornalin in the Valais region, enabled to show the high impact of water restriction and magnesium deficiency on the physiology of cv. Cornalin. Regions with stronger water restriction had lower vigour. In moderate water constraint, appeared a plateau with optimum residual sugar and total acidity levels in terms of must quality. Ten plots were under Mg deficiency. The intensity of Mg deficiency was growing from up- to downstream parts of the Valais region. Highest Mg deficiencies were observed in plots under lower water restriction. A relation between rachis necrosis and Mg level in leaves was established. Mg level was a good indicator of grape quality: total acidity was higher (+1 g/l as tartaric acid) and residual sugar content lower (-1 °Brix) when Mg deficiency symptoms on leaves were the highest ( 75 % of the canopy), in comparison to a situation without Mg deficiency.