USE OF MOLECULAR MARKERS IN PLANT-POPULATION BIOLOGY - PROCEEDINGS OFA SYMPOSIUM ORGANIZED BY THE ROYAL-BOTANICAL-SOCIETY-OF-BELGIUM, THE UNITY-OF-ECOLOGY-AND-BIOGEOGRAPHY (CATHOLIC-UNIVERSITY-OF-LOUVAIN) ANDTHE LABORATORY-OF-PLANT-GENETICS-AND-ECOLOGY (UNIVERSITY-OF-BRUSSELS), HELD AT LOUVAIN-LA-NEUVE, OCTOBER 18, 1996 - FOREWORD