Evolution of north American dent corn from public to proprietary germplasm

Current corn (Zea mays L.) hybrids are produced using proprietary inbred lines as parents. These proprietary lines are protected by U.S. Patent and/or the U.S. Plant Variety Protection Act (PVPA) and their use is restricted, but as protection expires these lines become available to the entire corn breeding industry. Our objectives were to gain understanding of this protected germplasm by utilizing pedigree information available in the U.S. Patent and PVPA records to enhance the use of this germplasm in new line development as the lines become publicly available. Ownership, derivation, and lineage of corn inbred lines protected by U.S. Patent or PVPA from 1980 to 2004 were surveyed. Thirty-three companies have protected 908 corn inbred lines and four of these companies: Dekalb Genetics (DK), Holden's Foundation Seeds (LH), Pioneer Hi-Bred (PH), and Syngenta (SG) originated 685 of them. We identified the most significant lines by their cumulative use as parents in the development of new lines. Much of today's germplasm originates from seven progenitor lines: B73, LH82, LH123, PH207, PH595, PHG39, and Mo17. The germplasm surveyed is grouped by pedigree lineage into Oh43, Lancaster, Oh07-Midland, lodent, Stiff Stalk, Commercial hybrid derived, and Argentine Maiz Amargo backgrounds, with new diversity emerging from the two latter groups. Recycling elite inbred lines using two-parent crosses followed by pedigree breeding was the most prevalent method of new line development.