Résumé
The invention relates to the use of a gene encoding a new outward potassium channel of Vitis vinifera for modifying at least one phenotype linked to the size and organic acid composition of grape berries. The gene is used to increase the size of the berries and the tartaric acid build-up therein. For this purpose, for example, the gene product is overexpressed by transgenesis. The invention also relates to a label comprising a nucleotide sequence encoding a polypeptide sequence that is at least 40 % identical to a polypeptide sequence deduced from gene VvSOR (SEQ ID NO 1). The label enables genes to be identified in other plant species, which genes code for new potassium channels identical to the grape berry potassium channel in order to modify the size and/or organic acid composition of plant storage organs.