Das Projekt "Genfluss in ausgewaehlten Nutzpflanzen der Schweiz und verwandten Unkraeutern, Risikoeinschaetzung fuer den Feldanbau von genetisch veraenderten Pflanzen in der Schweiz - Phase 2" wird vom Umweltbundesamt gefördert und von Universite de Neuchatel, Institut de Botanique durchgeführt. Aim: Evaluation of gene flow from crops to related weeds under regular agricultural conditions. Means: 1) bibliographical database, 2) field work: collection of wild relatives in zones of contact; screening for hybrids by the methods of biometry and genetics/ elaboration of distribution maps and of risk indices (Dpdf codes) as a synthesis of all the gathered data. Evaluation of risk of gene flow between crops and wild relatives by sexual reproduction is carried out in a first step by bibliographical work and herbarium examination. Then, spontaneous occurrence of the crop and the wild relatives is censused on test areas. Populations of the wild species close to the cultivated field are sampled. Depending on the species, the plants themselves or their progeny are are analysed in order to detect spontaneous hybrids or introgressive individuals. Moreover, artificial crosses and natural hybridisations are carried out. The synthesis of the results is expressed by risk indices (Dpdf) codes, which translate hybridisation rate with the local flora, the risk of escape of diaspores in the wild and the distribution frequency of wild relatives.^Moyen: 1) base de donnees bibliographiques, 2) travail de terrain: collecte de plantes sauvages proches dans des zones de contacts, recherches d'hybrides par des approches en biometrie et des analyses genetiques/ elaboration de cartes de distribution et d'indices de risques (codes Dpdf) qui synthetisent l'ensemble des donnees. (FRA)