Plant material

Fruiting cuttings of Vitis vinifera L. cv Cabernet Sauvignon (Ollat and Gaudillère, 1998) were grown in a greenhouse, in 0.5 L pots containing a mixture of perlite, sand and vermiculite (1:1:1). A drip irrigation system supplied water and a complete nutrient solution to the roots five times a day all along the experiment, avoiding any water or nutrient shortage. All fruiting cuttings bore only one single cluster and lateral shoots were removed as soon as they appeared during growth. Before the experiment, the tip of each shoot was removed as soon as 16 leaves per plant were produced to maintain approximately the same leaf area in all plants and a high leaf to fruit ratio (Ollat and Gaudillère, 1998). Therefore, all bunches were assumed to experience neither water nor assimilate limitation. In addition, the fruit cuttings were selected on the basis of similar vegetative growth and vigor as well as size and compactness of bunches.