during this period: Yield gains were 18% for rice, 30% for corn and 43% for sweet potato. The study argues that improved varieties which had been introduced due to stricter plant variety protection contributed to this development, and that 74 million people could be fed with the additional sweet potatoes. However, in the case of sweet potato that had the highest gain, no new variety had been protected and also for the other crops, productivity gains can be explained with other factors. A Study published by an Asian NGO finds that implementation of UPOV 91 in Vietnam did not lead to an increase of investment in breeding or in gains of productivity. Instead, it strengthened international commercial breeders at the cost of weakening the public breeders and threatening the farmers' seed sector. Impacts on food security and poverty reduction Smallholder farmers in the global South are amongst the groups most prone to poverty and hunger. They predominantly rely on seeds that are produced by farmers themselves, often also including varieties originally bred by public and private breeders. These farmers’ seed systems are often highly resilient and more accessible to famers than seeds offered by breeding companies. Through the implementation of strict plant variety protection in line with UPOV 91, and the restrictions on the use, exchange and sale of farm-saved seeds, farmers become more dependent on the seeds offered by breeding companies which often are unaffordable for the most vulnerable groups. As a consequence, adherence to UPOV would most likely have negative effects for poverty reduction and food security in developing countries. The risk for food security that come with the implementation of strict regulations for plant variety protection might be an important reason why many countries of the global South hesitate to join UPOV or to update from UPOV 78 to UPOV 91 (APBREBES 2021). The UN Special Rapporteur on the Right to Food, Olivier De Schutter, came to similar findings in his study of UPOV in 2009. He found that IP-related Monopoly rights could cause poor farmers to become "increasingly dependent on expensive inputs" and at risk of indebtedness. Further, the system risks neglecting poor farmers’ needs in favour of agribusiness needs, jeopardising traditional systems of seed saving and exchange, and losing biodiversity to "the uniformization encouraged by the spread of commercial varieties. In a report from 2009 the UN Special Rapporteur on the Right to Food, Olivier