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a Dept. of Horticulture and Crop Science, Ohio Agricultural Research and Development Center, The Ohio State Univ., Wooster, OH 44691
b USDA-ARS, Dep. of Agronomy, Iowa State Univ., Ames, IA 50011
c Illinois Foundation Seeds, Champaign, IL 61824
* Corresponding author (pratt.3{at}osu.edu)
GEMS-0002 (Reg. no. GP-400, PI 632413) is a maize (Zea mays L.) partially inbred germplasm line released by The Ohio State University (OSU) Ohio Agricultural Research and Development Center (OARDC) in accordance with the Germplasm Enhancement of Maize (GEM) protocol (Pollak, 2003). GEMS-0002 was released in March 2002 for use in the development of genetically diverse, elite, maize parental lines.
An S2 breeding line (OSU 43-2) was selected from GEM breeding population FS8A(S):S09 using pedigree selection methods. FS8A(S) is a synthetic population released by the University of Florida in 1988. Its pedigree consists of approximately 35% southeastern United States, 23% U.S. Corn Belt, and 42% tropical maize germplasm (Horner, 1990). S09 is an Iowa Stiff-Stalk Synthetic (BSSS)-related proprietary inbred. Thus, the source population was estimated to be comprised of approximately 62% Corn Belt Dent germplasm (50% BSSS-related, plus an additional 11.5% diverse Corn Belt Dent containing a high proportion of inbred C103A), 17.5% southeastern U.S., and 21% tropical maize germplasm. FS8A(S) was noted in earlier research (Dudley et al., 1996) as a population containing favorable alleles not present in elite Corn Belt hybrids. Breeder seed was increased by controlled full-sib pollination of nearly 200 S3 plants in the 2002 OSU nursery. Seed for distribution was increased by controlled full-sib pollination at the USDA-ARS nursery in Ames, IA, during 2003 and 2004. GEMS-002 is an S3 bulk composite that relates back to the S2 line OSU 43-2, theoretically 75% homozygous. According to GEM protocol (Pollak, 2003), S2 lines displaying agronomic variation are selected for release so that further inbreeding and selection may be practiced.
Several thousand plants from the GEM FS8A(S):S09 breeding population were grown at the OARDC in 1997 and 441 S1 progenies were produced by self-fertilization of S0 plants. The progenies were planted in single-row plots in the 1998 field nurseries in Iowa and Ohio. Two plants were self-pollinated per row and visual selection for agronomic traits was undertaken at both locations. Additionally, selection for resistance to green-snap was practiced in Iowa, and selection for resistance to Cercospora zeae-maydis (Tehon & Daniels) infection (causal agent of gray leaf spot) and to infestation of tassels by corn leaf aphids [Ropalosiphum maidis (Fitch)] was practiced in Ohio. Postharvest selection for good ear fill, sound kernels, and absence of ear rot occurred at both locations. S2 progeny lines (70 from Iowa and 100 from Ohio) were planted in the winter (1998–1999) topcross isolation nursery and testcrosses were made using the elite proprietary inbred LH185, a non-BSSS related line.
Performance trials were conducted in 1999 at Limagrain Genetics test-sites near Savoy and Clay City, IL; Hedrick, IA; and Shelburn and Worthington, IN; as well as at USDA-ARS sites near Carroll, Crawfordsville, and Rippey, IA; and at OSU sites near Custar, South Charleston, and Wooster, OH. The OSU 43-2/LH185 testcross was fourth among the top five experimental entries yielding 10128 kg ha–1, within 6% of the mean of the commercial checks (10723 kg ha–1), evaluated across a total of 10 locations in 1999 (LSD at P < 0.05 = 1016 kg ha–1). Commercial check hybrids in 1999 were LH198/LH185, LH200/LH262, Pioneer brand 3163, Pioneer brand 3223, and Pioneer brand 33G26.
S2 progenies that produced testcrosses in the top 10% for yield in the 1999 trials were selected and testcrossed to two non-BSSS proprietary inbreds (Golden Harvest IN504 and IN354) during the winter season of 2000–2001. Performance trials were conducted in 2001 at USDA-ARS test-sites near Ames and Crawfordsville, IA; at OSU sites near Wooster, OH; and at Golden Harvest sites near Cerro Gordo, Clinton, Mt. Erie, and Stonington, IL. Testcrosses with OSU 43-2 had the highest grain yield performance of the experimental testcrosses (8090 and 8171 kg ha–1), equal to 95 and 96% of the mean of the commercial checks (8466 kg ha–1), respectively, across seven locations in 2001 (LSD at P < 0.05 = 1016 kg ha–1). Commercial check hybrids in 2001 were Pioneer brand 3223, Pioneer brand 33G26, Pioneer brand 34B23, LH198/LH185, and LH200/LH262.
GEMS-0002 has demonstrated good combining ability with three non-BSSS proprietary inbred testers (Mo17 and Oh43 related). Average yield of the testcrosses across several states in the central and eastern Corn Belt during two seasons (1999 and 2001) was 95% of the mean of commercial check hybrids. Yields were equivalent or higher than those of the checks in test sites that experienced drought stress, and below that of the checks at the highest yielding test sites of 2001. Moisture content of the testcrosses was consistently below the average of the check entries at 158 vs. 183 g kg–1 in 1999 (LSD at P < 0.05 = 10 g kg–1), and 200 vs. 225 g kg–1 in 2001 (LSD at P < 0.05 = 10 g kg–1). Stalk lodging was approximately equal to that of the commercial checks' mean (1 vs. 3% and 9 vs. 9% in 1999 and 2001, respectively). Root lodging was negligible for both the testcrosses and commercial checks in the majority of tests.
Mid-silk date of GEMS-0002 is approximately 3 to 4 d earlier than that of B73 in Ohio across three seasons and 2 d earlier in Ames, IA, across two seasons. The mean plant height in 2003 across Ohio and Iowa nurseries in 2003 was moderate (185 cm), and ear placement was slightly below mid-plant height (86 cm). These values were both approximately 15 cm lower than the respective values for inbred B73. Ear and kernel characteristics of S2 and S3 populations were determined across 2002 and 2003 seasons from samples obtained in the OSU nursery near Wooster. Cob color is uniformly white and ears generally display 12 or 14 kernel rows (mean = 12.8 and range = 10 to 16) on pointed ears 13 cm in length and 3.8 cm wide. Kernels of GEMS-0002 are yellow-orange to orange in color and are slightly dented to flinty. The average weight of 100 kernels is 19 g. Grain protein composition (dry matter basis) is 129 g kg–1 (20 g kg–1 above B73), and average density is 1.35 g cm–3 (0.05 g cm–3 above B73). Kernel oil content (40 g kg–1) is essentially the same as that of B73.
GEMS-0002 is a prolific line that displays upright, dark green leaves. Ligules are cupped around the stalk. Moderate amounts of pollen are produced in tassels containing approximately seven branches. The color of silks and anthers is yellow. Susceptibility to temperate rust [incited by Puccinia sorghi (Schwein)] has been noted.
GEMS-002 is intended as a breeding resource for the improvement and diversification of elite, non-‘Lancaster Sure-Crop’ related inbreds. The line is unique in that it displays exceptionally early maturity and all-around agronomic quality for a line with such a high proportion of exotic germplasm in its pedigree. These attributes make it a potential breeding resource for programs throughout the majority of temperate maize producing regions. It is recommended that it be introduced into breeding programs by crossing with elite inbreds followed by modified pedigree selection. Using this method, it is anticipated the agronomic characteristics can still be improved since only one cycle of selection has been practiced. Requests for seed should be directed to Mr. Mark Millard, North Central Regional Plant Introduction Station, Iowa State University, Ames, IA 50011-1170. Recipients of seed are asked to make appropriate recognition of the original seed source if it is used to develop a new population, parental lines, or hybrids.
ACKNOWLEDGMENTS
We thank the GEM cooperators whose participation in the project made it possible for us to use FS8A(S):S09. We especially thank the USDA-ARS GEM cooperator grants program for funding support and GEM cooperators from Limagrain Genetics, Inc. and Central Golden Harvest, Inc., for in-kind support. We also thank Mike Blanco, David Francis, and Rouf Mian for reviewing an earlier draft of the manuscript. Mark Casey, Mack Shen, and Penny Meyerholz provided invaluable technical assistance. Mark Millard performed seed increase in the 2003 and 2004 Ames, IA, nurseries. Approved for publication as journal article No. HCS 04-10. The mention of firm names or trade products does not imply that they are endorsed or recommended by The Ohio State University over other firms or similar products not mentioned.
NOTES
Accepted for publication March 31, 2005.
REFERENCES
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