1. School of Agriculture, Aristotle University, 541 24, Thessaloniki, Greece; AMPELOENIKI Ltd., Viti-vinicultural research centre, 570 01 Thessaloniki, Greece; Agricultural University of Athens, 75 Iera Odos, 118 55 Athens, Greece; and ENITA de Bordeaux, 1 Cours du Général de Gaulle, CS40201, 331 75 Gradignan-Cedex, France