【正文】 (4) subsidiaries of foreign seed panies which want protection of their varieties and breeding lines in order to enter the Latin American seed markets。 (2) domestic cultivators of fruit and cut flowers for whom PBR protection is a condition to improve access to breeding lines and varieties from foreign breeders。 (3) the access to public germplasm。 rights (PBR) system is in use in most OECD countries as well as in some developing countries, but it is controversial. Private seed firms advocate PBR as it would stimulate innovation in plant breeding. Others argue that PBR may hamper the seed supply to farmers and may decrease geic diversity. A notable problem in the controversy is that empirical evidence on the impact of PBR is lacking. A recent study has attempted to collect some experiences in Latin America, with an emphasis on Argentina. In early 1995, 27 countries had PBR legislation enforced and were member of the International Union for the Protection of New Varieties of Plants (UPOV). Apart from these countries, Zimbabwe and Chile also have an operational PBR system, and, due to the new GATT agreement, many more countries will follow suit. Even though the PBR system is being considered by many countries, knowledge about its socioeconomic effects is poor. Apart from one or two studies on the effects of PBR in the USA, no assessment studies have been carried out. This situation was the reason for the InterAmerican Institute for Cooperation on Agriculture (IICA, Costa Rica) and University of Amsterdam, the Netherlands, in collaboration with researchers in five Latin American countries, to collect information on the debate and impact of PBR in Latin America. The study, carried out in 1994, tried to find data on the effects of PBR on: (1) investments in plant breeding by private seed panies。 ? rules for accession to the Convention, national treatment and priority of applications. The following section provides a general overview on important amendments brought about by the 1991 Act. With regard to the standard criteria for protection, no major changes were made in 1991. However, it was decided to introduce a number of de?nitions, among them de?nitions of ‘‘breeder’’ and ‘‘variety’’, which further clari?ed the UPOV system and contributed to harmonization in its operation. Important clari?cations were also made with regard to the scope of protection, to the varieties and to the material of these varieties covered by a breeders right. In that context, the concept of Essentially Derived Varieties (EDV) was developed: The EDV concept implies that a variety which is deemed to be essentially derived from a protected variety (the initial variety) may qualify for protection. Its exploitation, however, is subject to the authorization of the breeder of the initial variety. The aim is to provide suitable incentives to all forms of plant breeding, thereby also facilitating the integration of biotechnological inventions, which may be protected by patents, into modern plant breeding. In respect of the exceptions to the breeders right, their scope was rede?ned. It is now speci?ed that the relevant acts done for experimental purposes or done privately and for nonmercial purposes are not subject to the breeders right. The latter exceptions may be relevant, for example, in relation to subsistence farming or to private gardening. With regard to the use of a protected variety for breeding other varieties, the authorization of the breeder of the protected variety is not required in either the 1978 Act or in the 1991 Act (‘‘breeders exemption’’). In addition, acts done with these varieties (. marketing) do not require the authorization of the breeder of the protected variety except for the circumstances speci?ed in the 1978 Act or in the 1991 Act. The 1991 Act speci?es that the authorization is required, inter alia, for the mercial exploitation of an essentially derived variety. As an optional exception to the breeders right, a provision on farmsaved seed was introduced which allows UPOV members to permit farmers, under certain conditions, to save seed within reasonable limits and in a way which safeguards the legitimate interests of the breeder. The minimum duration of protection was extended to 25 years for varieties of trees and vines and to 20 years for other varieties. Of particular relevance in the context of this article is the provision on the minimum number of plant genera and species whose varieties must be protected. When the Convention was revised in 1991, speci?c provisions on the examination of the application for a breeders right were introduced which offered a broad range of options for variety testing involving cooperation, for example, with breeders and other authorities on a national and international level. Thus, no particular diffculty was seen in providing protection for varieties of all plant genera and species. Accordingly, the 1991 Act requires the grant of protection for the varieties of all plant genera and specie