From the UPOV Act of 1978 to the Act of UPOV 1991, some fundamental changes were made:
- Farmers cannot freely save seeds from protected varieties for their own use: UPOV 91 restricts the rights of farmers to freely use their seeds or other propagation material for further cultivation. This right is limited to those countries which make special provision for it. Article 15.2 of UPOV 91 provides for an optional exception “to permit farmers to use for propagating purposes, on their own holdings, the product of the harvest which they have obtained by planting, on their own holdings, the protected variety”, which member countries could implement, if they wish. But this exception is very limited. It excludes propagation material which is not the product of the harvest (eg. fruits or berries) and it prohibits all exchange and selling of protected material - as farmers are only allowed to reuse their seed on their own holding. And in addition this exception has to be implemented “safeguarding of the legitimate interests of the breeder,” which means that even where seed saving is allowed, at least bigger farmers have to pay royalties to the breeders.
- Varieties can be patented: Plants, and in some countries also varieties, can also be patented now, in addition to PVP protection. Under previous UPOV Acts there was a specific ban on such 'double protection', while for UPOV 91, this ban was deleted.
- Harvest belongs to the breeder: UPOV 91 also extends breeders' rights to "harvested material" in case of unauthorized use of the propagation material. If the farmer sowed his or her field with a PVP variety without paying the royalty fee, the breeder can claim ownership of the harvest and the products made from the harvest.
- Further breeding is restricted: Anyone using a PVP variety in breeding has to make major changes or else the 'new' variety will not be considered 'new', but it will be considered an 'essentially derived' variety, falling to the ownership of the first breeder. The idea, according to UPOV, is to discourage small changes in the variety's characteristic from being passed off as true innovation.
- GRAIN (1998) Ten reasons not to join UPOV