The legal act that sets the basis for the protection of plant varieties at international level is the International Convention for the Protection of New Varieties of Plants (UPOV): http://www.upov.int/upovlex/en/acts.html
The 1991 version of the UPOV Convention is in force in most countries, whereas the 1978 UPOV continues to have legal effects in few countries. For the UPOV Members see http://www.upov.int/upovlex/en/notifications.jsp
2. Other international acts
Other legal acts that influence the application of plant variety rights are the Trade Related Intellectual Property Rights Agreement (TRIPS), the Convention on Biological Diversity (CBD), the Nagoya Protocol implementing art. 15 of the CBD and the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA). Trade agreements may further influence PVP to the extent that they impose obligations on plant variety rights.