Availability and Analysis of Proprietary Dent Corn Inbred Lines with Expired U.S. Plant Variety Protection

Abstract

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.

Identification of heterotic patterns between expired proprietary, NDSU, and industry short-season maize inbred lines

“…Lp5, therefore, seems to be in agreement with the PVP documents as presented in Table 1 (Mikel 2006). DK78010 combined well with both Iodent type tester T1 and SS tester T7.…”

“…Our evaluation infers that PH207 has a non-SS background, in addition to Iodent. NK779 combined well with the SS tester T4.NK779 evaluation seems to agree with the non-SS heterotic group assignation, which supports the line's MN13 and unrelated composition (Mikel 2006).…”

“…Inbreds that were combining well with two contrasting testers (belonging to different heterotic groups) are also presented in Table 1. Mikel (2006) and GRIN have proposed heterotic groups of ex-PVP inbred lines based on the disclosure made by industry. Our study wanted to validate the classification.…”

“…The combining ability of DJ7 was above average with SS tester T2. Therefore, it showed the inbred may not belong to the SS group as published by Mikel (2006). The unrelated proportion of DJ7 could combine well with SS testers.…”

“…Inbred NK807 combined well with non-SS tester T5, therefore,it could belong to the SS group. However, NK807 has Lancaster background so further testing might be needed (Mikel 2006). DKFAPW combined well with the Iodent tester T3.…”