1970 USDA seed patent law allowed farmers to keep seeds
In 1970, Congress passed the Plant Variety Protection Act (PVPA). This Act empowered USDA to grant Certificates of Protection for novel sexually reproducing plant varieties grown from seed.16 The Certificates conferred exclusive marketing rights to the breeder for an 18-year term (subsequently amended to 20 years). However, the certificates established two critical exemptions: 1) farmers must be allowed to save seeds for replanting; and 2) patented varieties must be made available to researchers.
With these exemptions, Congress explicitly recognized that farmers and public interest breeders were vital partners in the continuing improvement of plant varieties and enshrined in law the millennia-old right of farmers to save seeds. The PVPA balanced the interests of seed firms, farmers, and public sector plant breeders. On the one hand, it granted strong protections to the seed industry by making it illegal for one firm to illicitly multiply and sell a seed variety developed by a corporate competitor. At the same time, Congress provided exemptions to farmers and breeders. As noted above, farmers could save and replant PVPA protected seed, while plant breeders could utilize protected varieties in further breeding work to develop still better plants. (A 1994 amendment to the law prohibited farmers from selling PVPA protected seed to other farmers, which the original PVPA had allowed)
CENTER FOR FOOD SAFETY & SAVE OUR SEEDS, "Seed Giants Vs. US Farmers" 2013 http://www.centerforfoodsafety.org/files/seed-giants_final_04424.pdf, p. 14 [verified 4/15/14]