The paper applies the framework of semicommon property arrangement to analyze the effects of the expansion of property rights in the development, exchange and conservation of crop genetic resources.With the rise of biotechnology in plant breeding and the threat of genetic erosion in agro-biodiversity rich areas, strong intellectual property rights have emerged for crop innovation while national sovereign rights over raw genetic resources have been created with the Convention of Biological Diversity (CBD). The new international regime should provide effective incentives for the sustainable use and conservation of crop genetic resources, but it may be ill suited in a field where 1) crop development is a cumulative process based on a networked environment of innovators and 2) traditional farmers and public institutions are still relevant stakeholders in crop development sector.The understanding of crop genetic resources management as a semicommon arrangement may help to unveil normative prescriptions in order to avoid the distort effects of the enclosure. New institutional devices, which guarantee access to germplasm among traditional farmers and the public agricultural research system, may limit the distortions caused by the expansion of exclusion rights.The new FAO Treaty (signed in 2001), which sets up a multilateral system of facilitated germplasm exchange and affirms the concept of Farmers' Rights, seems to be an institutional mechanism that shares this policy vision.