Botanical Files. A study of the real chances for spontaneous gene flow from cultivated plants to the wild flora of the Netherlands

Separate ‘Botanical files’ have been made for 42 species of cultivated plants. Each file gives information about the cultivated plant itself (use, origin, etc.), its wild relatives in the Netherlands, a report on actual hybridization and/or crossing (indicating gene flow by pollen), and observations on escapes from the field to nature (indicating gene flow by diaspores); the information is summarized to a conclusion and a numerical code, indicating the possible ecological effects of the cultivated plant on the wild flora of the Netherlands. This study was especially undertaken for questions regarding biosafety research on Genetically Modified Organisms (GMO’s). The sources are the herbarium collections of the State Herbarium at Leiden, floristic archives and botanical literature, as well as expert judgment on the flora of the Netherlands and crop plants. An important consideration is that the absence of certain hybrids in the State Herbarium can be interpreted as a decisive indication that such a hybrid does not occur in the wild in the Netherlands. The botanical files show that in c. 50% of the cases no gene flow is expected; in c. 15% of the cases small, often local-scale effects are expected; in c. 25% of the cases considerable gene flow to the wild is expected; in c. 10% of the cases further research should be done before a definite conclusion can be drawn (most of the cases need further taxonomic research).