Availability and analysis of proprietary dent corn inbred lines with expired U.S. plant variety protection

Current U.S. commercial hybrid corn (Zea mays L.) is produced using proprietary inbred corn lines as parents. Most proprietary corn inbred lines have been protected by the U.S. Patent and/or U.S. Plant Variety Protection Act (PVPA) since approximately 1980. Currently there are 89 dent inbred corn lines (with more each year) whose intellectual proprietary protection has expired. These inbred lines are now available from the U.S. National Plant Germplasm System with freedom to operate for applications in research, plant breeding, and direct commercial use. This study facilitates an understanding of this germplasm by utilizing detailed pedigree and phenotypic information available from U.S. Patent and PVPA records to enhance their application to research and product development. This germplasm is mostly yellow dent and ranges in maturity from early (1000 heat units to mid-silk) to full (1708 heat units to mid-silk) season. These proprietary lines are from diverse backgrounds that include Iowa Stiff Stalk Synthetic, Argentine Maiz Amargo, Oh43, Minnesota 13, Iodent, Lancaster, Oh07Midland, Commercial Hybrid derived, and uncharacterized broad base sources from exotic, synthetic, and open pollinated populations.