Published online 21 November 2006
Published in Crop Sci 46:2555-2560 (2006)
© 2006 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
PLANT GENETIC RESOURCES
Availability and Analysis of Proprietary Dent Corn Inbred Lines with Expired U.S. Plant Variety Protection
Mark A. Mikel*
Dep. of Crop Sciences and Roy J. Carver Biotechnology Center, Univ. of Illinois, 901 S. Mathews Ave., Urbana, IL 61801 and Maize Lineage LLC, 3408 Mill Creek Ct., Champaign, IL 61822
* Corresponding author (mmikel{at}uiuc.edu)
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ABSTRACT
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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.
Abbreviations: DK, DEKALB Genetics • LH, Holden's Foundation Seeds • NCRPIS, North Central Regional Plant Introduction Station • NK, Novartis Seeds • PH, Pioneer Hi-Bred International • PVPA, Plant Variety Protection Act
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INTRODUCTION
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DARRAH AND ZUBER (1986) surveyed the American Seed Trade and found a diminishing role of public inbreds in commercial dent corn hybrid formulas. Other than the public inbred B73, very few public lines were used commercially. Shortly thereafter, molecular fingerprint analysis of commercial corn hybrids confirmed that public inbred lines were rarely used in commercial hybrids (Smith, 1988; Smith and Smith, 1991). This was because proprietary corn lines outperformed and subsequently replaced public inbreds in commercial hybrid formulas. The combination of PVPA and Patent protection of corn inbred lines, the absence of new elite public inbreds, and rapid expansion of proprietary product development programs resulted in a concomitant shift in the overall germplasm base into closed proprietary systems. Mikel and Dudley (2006) surveyed U.S. PVPA and U.S. Patent records and demonstrated that much of today's proprietary germplasm traces back to seven progenitor lines: B73, LH82, LH123, PH207, PH595, PHG39, and Mo17. Today's germplasm can be generalized into two somewhat divergent pools: Pioneer Hi-Bred (Maiz Amargo, Stiff Stalk, Iodent, and Oh07Midland lineages) and other proprietary entities outside of Pioneer Hi-Bred (Stiff Stalk, Lancaster-Mo17, and derived from Pioneer Hi-Bred hybrid 3535, 3558, and 3737 lineages). The public inbred line B73 was prominent in the development of stiff stalk germplasm within both programs.
U.S. Congress approved the PVPA in 1970; originally granting protection of registered germplasm for 18 yr and then in 1995 protection was extended to 20 yr (Janis and Kesan, 2001). Proprietary corn inbreds were not widely PVPA protected until after 1980. The PVPA does allow breeding of protected lines. This is common in crops where the registered cultivar is not patented and is directly marketed, as for example in soybean [Glycine max (L.) Merr.] and wheat (Triticum aestivum L). Commercial corn is marketed as an F1 hybrid of two inbred corn lines and, therefore, the PVPA registered inbreds are not directly identifiable or available. The originator controls access and use of these inbred corn lines. Companies at their discretion can allow use of PVPA/Patent protected corn lines through licensing, but, otherwise, there is no legal access to these inbreds for breeding.
In 1985 the U.S. Patent and Trademark Office facilitated the patenting of seed propagated plants and consequently most proprietary corn inbreds and some commercial hybrids have been patented (Janis and Kesan, 2001). The U.S. Patent grants protection for 20 yr from the date of application and, unlike PVPA, does not allow breeding rights (Evenson, 1999). The PVPA certificates of the first registered protected inbred lines have expired and these lines are now available for unrestricted use with additional lines added yearly.
Corn inbreds granted PVPA protection before 1985 were registered before the availability of U.S. patenting of corn became available. After 1985, protection of inbred lines can be from either or both U.S. PVPA or U.S. Patent protection and these dual protected lines are not acquirable until both sources of protection have expired. Samples of PVPA registered lines are deposited in the National Plant Germplasm System and held at the National Center for Germplasm Resource Preservation in Ft. Collins, CO. Upon PVPA certificate expiration, lines are transferred to the active site for maize curation, the North Central Regional Plant Introduction Station (NCRPIS) in Ames, IA for maintenance and distribution. Patented lines have seed deposited by the patent assignee with the American Type Culture Collection in Manassas, VA for distribution for use allowed by patent law, until the patent has expired and for general use thereafter, as long as applicable PVPA protection has also expired.
Mikel and Dudley (2006) found 908 proprietary corn inbred lines that are registered for either U.S. patent or PVPA protection. Protection is expiring on these lines and they are becoming available for research and commercial applications. Although dated by several cycles of recombination and selection, these lines can offer genetic diversity to programs that previously did not have access to them. As a consequence of being proprietary, little is known about these lines outside of the program of origin.
The objective of this work is to assist efforts in using this germplasm once protection has expired: (i) by drawing awareness to the availability of and how to obtain this germplasm; (ii) through studying their pedigree derivation, gain an understanding and classification of their backgrounds; (iii) and assembling phenotypic information to facilitate introgression into agronomic research and product development programs.
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MATERIALS AND METHODS
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Phenotypic information on these lines was derived from PVPA certificates available through the Plant Variety Protection Office. A listing of all PVPA protected lines is available at http://www.ams.usda.gov/science/PVPO/CertificatesDB.htm (verified 4 Sept. 2006). Table 1 summarizes information gathered from PVPA certificates: name of each line, last recorded owner in PVPA database, and pedigree derivation of the line. Other information includes maturity measured as heat units to 50% silk, number of kernel rows on the ear, kernel endosperm and cob color.
Figures 1
and 2
represent lines of stiff stalk and non-stiff stalk backgrounds, respectively. The lines with expired PVPA protection are in shaded boxes. The pedigree derivation of each line is shown. A best effort is made to link pedigree information in the PVPA certificate with other sources from the U.S. Patent Office, published literature, and information from PVPA certificates of other lines to facilitate tracing each line back to recognizable public inbred lines, land races, or synthetic populations. The inbreds are linked by descent, with each arrow originating at the parental line and pointing to its progeny. The background of some lines could not be determined or they were derived from unrelated or unfamiliar crosses, and these lines were not included in the figures.
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Fig. 1. Stiff Stalk Lines with expired Plant Variety Protection.  Public inbreds are noted by standard station release prefix. The PVPA lines with expired protection are shown in shaded boxes. Proprietary lines are from Asgrow Seed, DEKALB Genetics (DK), FFR Cooperative, Illinois Foundation Seeds (FR), Edward J. Funk & Son, Holden's Foundation Seeds (LH), Pfister Hybrid Seed, Claeys Semences, Novartis Seeds (NK), DowElanco, and Pioneer Hi-Bred International (PH). Arrow originates at parent and points to progeny. Pedigree derivation for each line is determined from Plant Variety Protection Act (PVPA) certificates referenced in Table 1, except where noted.  Smith et al., 1997;  PVPA certificate number 8800152; ¶PVPA certificate number 9500208; #Gerdes et al., 1993; PVPA certificate number 8700214; PVPA certificate number 9500211; PVPA certificate number 8700036; ¶¶PVPA certificate number 8700173.
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Fig. 2. Non-Stiff Stalk Lines with expired Plant Variety Protection. Public inbreds are noted by standard station release prefix. The PVPA lines with expired protection are shown in shaded boxes. Proprietary lines are from Asgrow Seed, J.C. Robinson Seed (JCR), DEKALB Genetics (DK), Holden's Foundation Seeds (LH), Iowa State, Novartis Seeds (NK), Pioneer Hi-Bred International (PH), Quality Research Associates, and Rothermel Seed. Arrow originates at parent and points to progeny. Pedigree derivation for each line is determined from Plant Variety Protection Act (PVPA) certificates referenced in Table 1, except where noted. Smith et al., 1997; Gerdes et al., 1993; ¶Smith and Smith, 1987; #PVPA certificate number 9800383; PVPA certificate number 8700197.
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RESULTS AND DISCUSSION
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The 89 released lines in Table 1 are predominately yellow dent corn lines registered to 15 seed corn companies. Four companies, Pioneer Hi-Bred (29 registered lines), Holden's Foundation Seed (21), DEKALB Genetics (14), and Novartis (11), developed 75 of these 89 lines. They were developed and registered during the transition from public to proprietary germplasm. Consequently many are first cycle proprietary lines with one or more public inbred line(s) as parents. Fifty originated from one or more proprietary inbred parental lines, 48 from one or more public inbred parents, 27 were derived exclusively from proprietary lines, and the derivation of 27 was entirely from public inbred parentage. The lineage of those lines derived from one or more pubic inbred corn lines frequently trace back to B73 (parent of 20 lines), Mo17 (12), A632 (8), B37 (5), W117 (5), A634 (3), H99 (3), CM105 (2), and B14 (2). Of the 29 Pioneer Hi-Bred registered lines used in this dataset, only five lines were derived from public inbred lines and these were B73, B37, B64, SD105, and A632. The recycling of public lines was not directly involved in the development of this set of Pioneer PVPA protected lines. It is ostensible that Pioneer Hi-Bred began using proprietary germplasm sooner than the rest of the American seed trade, perhaps one or two recombination cycles earlier.
These dent corn lines range in maturity from early (1000 heat units to mid-silk) to full season (1708 heat units to mid-silk). Kernel color is yellow with the exception of three white corn lines. Ear girth ranges from 10 to 22 kernel rows and cob color includes red, white, or pink. Sixteen lines were directly developed from wide or unrelated crosses consisting of exotic, synthetic/open pollinated, or competitor hybrid. Exotic germplasm used was Zapolote Chico (PHV63), Mexican Deep Kernel Open Pollinated (NK740), and Yugoslavian GLAMOS Open Pollinated (LP5). Synthetic and/or open pollinated populations used were Mankato Southern Dent (MKSDTE, PHG47), BS11(FR)C3 (LH93), ASA (LH61), BS16 (DJ7), Composite 800M (Lancaster background, DKMDF-13D), Composite 400M (DKMBPM), Iowa Long Ear (DK78371A), B-Line Composite (Synthetic from inter-mating 35 corn belt inbreds, DK4676A), and MDA-28 (BPA x EOOM Composite, DKMBNA). Competitor hybrids used were Pioneer Hybrid 3901, 3978, 3535, 3369, 3195, and 3199. These are diverse unrelated sources of germplasm that has been refined into what at one time were commercially elite lines.
The PVPA protection of these lines will have expired by the end of 2006. However, six of these lines are dual protected by both U.S. Patent and PVPA: DK78010 (U.S. Patent 4,654,466), DKHBA1 (4,594,810), PHK05 (4,806,669), PHK29 (4,812,600), PHR25 (4,806,652), and PHV78 (4,812,599). Patent protection has expired for DK78010 and DKHBA1, but has not expired for PHK05, PHK29, PHR25, and PHV78, which will remain under patent coverage until 2008. Corn lines whose protection has expired can be obtained through the United States Department of Agriculture NCRPIS at Ames, IA through their website http://www.ars-grin.gov (verified 4 Sept. 2006). Progenitors of much of today's elite germplasm, as well as a wide assortment of lines of many backgrounds, are available. This is a continuous process as more lines become available each year from the growing queue of registered lines with time-dependent expiration of protection. These lines have value in studies in entomology, weed science, plant pathology, physiology, plant nutrition, genetics, genomics, and breeding, such that interpretation of experimental results can have meaningful and relevant applications to today's germplasm. Certainly, these inbreds offer agronomists and corn breeders sources of elite diversity previously not accessible to their product development programs.
Use of this germplasm is but one way to invigorate corn breeding programs. Tapping exotic germplasm, exchange of proprietary corn lines between programs through licensing, and use of calculated wide breeding crosses are other options. This material has been discussed primarily based on their pedigree lineage. Little if any information is publicly available on their combining ability with other lines. To effectively breed with these lines there is a need to evaluate a diallel of representatives of the various backgrounds to gain a working understanding how they combine with each other and with today's elite corn lines in hybrid formulas.
These lines are dated by several cycles of recombination. Although this germplasm is antiquated, these lines were in many cases widely used as parents of commercial corn hybrids. This germplasm can invigorate many proprietary programs that have become banal from continuously recycling closely related lines. Ideally, by integrating this material into breeding programs, new opportunities for product improvement and discovery will be created.
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ACKNOWLEDGMENTS
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I wish to thank Candice Gardner, Mark Millard, and Stephen Smith for critiquing this manuscript and their comments have greatly improved this work. The assistance of Janice Strachan of the Plant Variety Protection Office is greatly appreciated. I wish to thank the Roy J. Carver Biotechnology Center of the University of Illinois for financing the publication of this research.
Received for publication May 31, 2006.
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REFERENCES
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ABSTRACT
INTRODUCTION
