Germplasm Enhancement of Maize

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Project Summary
Need for Research
Relevance to ARS
Potential Benefits
Anticipated Products
Scientific Background
Research Procedures
Literature Cited
Concern Statement

GEM Project Plan

Project Summary

The Germplasm Enhancement of Maize (GEM) Project is a cooperative research effort of the USDA-ARS, land grant universities, private industry, and international and non-governmental organizations to broaden the germplasm base of maize.  Genetic uniformity can lead to vulnerability to crop pathogens, insects, and abiotic factors, thereby compromising food security.  Breeding with unadapted germplasm is a long term process requiring a coordinated multi-site effort to develop procedures for breeding methodology, conduct nurseries, evaluation trials, and laboratory analyses for trait evaluation.  In addition to reducing genetic vulnerability, broadening the germplasm base can provide unique traits, thus enhancing value to our stakeholders, and ultimately to the consumer.  The products of the GEM Project include new sources of germplasm that will be available to all researchers free of charge through the North Central Regional Plant Introduction Station (NCRPIS).  Released germplasm is expected to have immediate utility for incorporation into corn breeding programs by the commercial and public sectors.  Commercial products are expected to be derived from the immediate progeny of GEM germplasm crossed to existing adapted lines.  New research information will be generated and shared with the scientific community, and includes (i) characterization of germplasm for agronomic performance and traits, (ii) breeding methodology for enhancement of unadapted (exotic) germplasm, and (iii) germplasm with unique value-added traits (VAT’s) for further research applications, e.g. genomics research.  Greater usage of released germplasm will ultimately broaden the germplasm base of maize.  The success of GEM may serve as a future model for germplasm enhancement of other crop species.   



Objective 1:     Coordinate the Germplasm Enhancement of Maize (GEM) Project by managing an extensive multi-site cooperative breeding and information sharing program with public and private cooperators.

Objective 2:     Develop genetically enhanced populations and inbred lines from GEM and other breeding crosses.  

Objective 3:     Evaluate genotypes in the breeding program for yield, agronomic traits, biotic and abiotic stress (including mycotoxins), and value-added traits (VAT).


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Need for Research

Description of Problem to be solved:

The U.S. maize germplasm base is extremely narrow and focuses on the development of inbred lines from historically important lines such as B73, Mo17, OH43, and A632.  In terms of food security and the national interest, it is critically important to have a more diverse maize germplasm base.  Although there are over 250 races of maize, the commercial sector focuses primarily on one race - Corn Belt Dent.  Exotic germplasm often refers to germplasm that originates outside the U.S.  But a broader definition of exotic germplasm by Hallauer (1978) is appropriate and can be considered to be “germplasm that does not have immediate usefulness without selection for adaptation to a given environment.”  Thus germplasm that originates in the southern US and is never used in a commercial breeding program can be considered exotic.  The process of introgressing exotic material into adapted germplasm is long-term by nature, and is too costly for any one program to successfully pursue alone.  Our understanding of the traits and/or characteristics that exotic germplasm can contribute to elite germplasm development is limited.  Effective breeding methodology to utilize this material is not well developed.   Additional nursery sites and/or diverse selection environments may be required.  Pre-breeding and selection for adaptation is needed in order to address maturity and photoperiod issues.   Experimental hybrids containing exotic germplasm require extensive evaluation in order to identify and minimize the high genotype x environment interaction commonly associated with exotic, unadapted material. 

Broadening the germplasm base reduces the risk of genetic vulnerability, provides essential diversity for VAT’s, and increases the response to selection.  Although the importance of genetic diversity is understood by plant breeders, commercial breeding for diversity is not emphasized due to a necessary focus on rapid product development and breeding from an elite narrow based germplasm.  Therefore the two key questions are (1) Can diverse sources of germplasm be found and utilized in a breeding program while maintaining performance goals, and (2) What is the best methodology to utilize genetic diversity?


Relevance to ARS National Program Action Plan:

This program supports the Mission Statement of NP301 to safeguard and utilize germplasm to enhance agricultural productivity in order to assure a high quality, safe supply of food and industrial products.  It also supports the Vision of NP301 to furnish raw materials and tools for crop improvement.   The program is closely allied to Component I (Genetic Resource Management), and to Component IIb of NP301 (Genetic Improvement).  Component IIb is also closely allied with IIa (Genomic Characterization).  The general objectives of IIa and IIB are to increase the long term economic value of genetic material; development of superior crops that are competitive in world markets is a desired outcome.  While Genetic Improvement focuses on germplasm development and classical plant breeding, Genomic Characterization focuses on identification of important genes, gene sequences, and elucidation of genetic mechanisms.  The project also supports elements of NP303 (Plant Diseases), NP304 (Crop Protection and Quarantine), and NP306 (Quality and Utilization of Agricultural Products).


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Potential Benefits:

New, enhanced germplasm will be developed and made available to all researchers via the NCRPIS.  This will encourage greater usage of exotic material, ultimately broadening the germplasm base.   A safer and more secure food supply will result from reduced genetic vulnerability to diseases, insects, and abiotic stress. Improved collaboration and research synergies with plant breeders, pathologists, entomologists, and researchers involved in plant genomics are foreseen.  Expected benefits include germplasm improved for yield, stability of yield, value added traits, disease and insect resistance, and resistance to mycotoxin production (aflatoxin and fumonisin).   More cost efficient maize production is an expected benefit, particularly for application of enhanced germplasm to sustainable agricultural systems.   A greater understanding of appropriate breeding practices for exotic germplasm will result.  


Anticipated Products:

New enhanced germplasm with improved agronomic, VAT’s, and other traits will be publicly available, via the NCRPIS.  While most of the germplasm is not expected to be directly useable in commercial products, GEM lines will be developed that are desirable sources for immediate introduction to breeding programs.   The germplasm will provide a source of novel traits and allelic diversity for applied breeding and basic research programs.  Products will also benefit researchers in sustainable agriculture programs who require germplasm sources for development of open pollinated varieties with value added traits and weed competitiveness.  Some of the anticipated products include sources of germplasm (S3 lines, broad based breeding crosses, and synthetics) with resistance to drought, heat, and to mycotoxins such as aflatoxin and fumonisin.  New sources of European Corn Borer and corn ear worm resistance have already been identified; expectations that corn root worm resistance will follow are based on preliminary rootworm studies by USDA-ARS researchers in Missouri.  New S3 lines for grey leafspot resistance and anthracnose are now in the advanced yield trial stages, and high yielding sources of disease resistance are expected in the next 1-2 years.  VAT’s include high amylose, and starch with unique thermal properties, high protein, oil, silage, and genetically low phytate grain. 



Our stakeholders include public and private researchers, collaborators, administrators, and educators.  The germplasm is used for research and development programs in public and private corn breeding programs, as well as for basic research projects such as inheritance studies, molecular marker research, and trait development.  The diverse nature of the germplasm is sought by scientists from a variety of disciplines, including plant breeding and genetics, entomology, agronomy, plant pathology, starch, oil, and protein chemistry, food science, weed science, plant physiology, seed science, evolutionary biology, and ethnobotany.  Educators routinely visit the GEM Project nurseries and trials with students as part of their university plant breeding training.  Customers include a broad group of researchers and product development specialists interested in obtaining GEM Project germplasm, including the international community.  In the US, most major and many medium size seed companies are active supporters and customers of GEM and include companies such as Pioneer Hi-Bred Intl., Inc., Monsanto Company, Syngenta Seeds, Inc.,  Golden Harvest Research Inc, and NC+ Hybrids.  Most U.S. universities with public corn breeding programs such as the University of Illinois, Ohio State University, and the University of Nebraska are active customers or collaborators with the GEM Project. International customers include Empresa Brasileira de Pesquisa, Agropecuaria (EMBRAPA) in Brazil, AgriSource Co., Ltd. Thailand, and Instituto Nacional de Tecnologia Agropecuaria (INTA) Argentina, as well as companies in Argentina, and Mexico.  The superior germplasm developed benefits growers, producers, and end-use processors in the food, and non-food industries.  Consumers benefit from development of products with enhanced quality or nutritional properties, as well as from a safe and stable food supply.


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Scientific Background:

Coordinate the Germplasm Enhancement of Maize Project:

The issue of genetic vulnerability was always a major concern but came to light in maize following the 1970 epidemic of Southern Corn Leaf Blight in the US (Nat. Acad. Sci., 1972).  Surveys (Darrah and Zuber, 1985) indicate that the maize germplasm base is relatively uniform and has not changed appreciably.  A series of surveys determined that a small increase occurred in the amount of exotic germplasm used from 1984 to 1996.  Temperate exotic usage increased from 0.8% to 2.6%, and tropical exotic usage increased from 0.1% to 0.3% in the same period.  Although surveys of this type are highly subjective and depend upon a respondent’s interpretation of “exotic,” it is clear that genetic vulnerability remains a national issue impacting food security. 

The predecessor of GEM was the Latin American Maize Project (LAMP). GEM would not exist if the Latin American Maize Project (LAMP) had not come first. The LAMP project was a 5 year (1987-1992) combined effort of 11 Latin American countries and the U.S. (12 members) to evaluate over 12,000 accessions comprising 74% of the known races of maize (Salhuana and Sevilla, 1995).  The LAMP project was funded by Pioneer Hi-Bred and administered by the USDA.  From over 12,000 accessions evaluated during LAMP, 268 accessions were identified with favorable yield and agronomic performance.  From these 268 accessions, 51 were selected to initiate the GEM Project (Pollak, 2003). In addition, Dekalb donated 7 tropical hybrids as accessions to be used by GEM.  The GEM Project started in the 1993-94 winter nursery, and is considered the first coordinated international project for enhancing and evaluating a major world crop (Pollak, 2003).  The history and origin of LAMP and GEM is comprehensively covered in several papers (Pollak, 2003; Pollak and Salhuana, 2001; Salhuana and Sevilla, 1995).

The cooperative GEM network consists of private companies, public cooperators, international, and non-governmental organizations.  The operational foundation of GEM is based on “in-kind support,” and consists of essential breeding and testing services provided by the companies.  Private companies provide proprietary germplasm by crossing their material to GEM accessions to generate breeding crosses for development.  This material is freely shared with other GEM Cooperators for research, or further development.  Participating companies may use the genetic materials in their breeding programs for internal proprietary development. In return, agreed upon materials designated as “in kind support” are returned to the GEM Coordinator.  It is imperative that all in-kind support commitment be clearly understood by the Cooperators and the Coordinator. GEM Cooperators agree that materials are not to be shared outside of the GEM participant group prior to public release (via the NCRPIS) - the ultimate goal of GEM.  GEM Cooperators have working access to germplasm approximately two years prior to public release, and germplasm recipients benefit from the long term commitments the participants have made.

In addition to GEM, a European collaborative program has been involved on a local level to use exotic germplasm for broadening the germplasm base (Gallais and Monod, 2001).  The French Cooperative Program Groupe INRA, and Promais, a group of 13 private breeding companies, formed a collaborative group in 1985 to collect, multiply, and evaluate early exotic material.  The impetus for this effort was the genetic uniformity of French flint germplasm in which 85% of the commercially grown crop involved a single inbred male, F2.  The germplasm collected included land races, synthetics, and tropical x temperate pools, mostly from CIMMYT.  Unlike GEM, companies did not provide proprietary germplasm, but assisted with per se evaluation, breeding, and trials with tester crosses.  Although their results provided positive correlation of per se and test cross performance (indicating additive effects), no hybrids were found (as of 2001) that out-performed the elite commercial check, F250xF252.

The benchmark of success in any breeding program is competitive yield (preferably better) with commercial products.  Several reports (Pollak and Salhuana, 2001; Pollak, 2003), have shown that GEM S2 topcrosses have out performed leading commercial checks in multi-site trials.   During the past 4 years (1999-2002), GEM topcrosses were identified that exceeded check means in a wide range of material including breeding crosses with accessions originating from the U.S., Brazil, Cuba, Mexico, Peru, Chile, and Uruguay (data on GEM web site: High yielding lines have also been identified from most of the tropical hybrid breeding crosses from the NC program; 30 lines are projected to be released in 2003.  Germplasm enhancement is a long term process; the early success of GEM may be attributed to using elite adapted lines crossed to the best accessions from LAMP.

Develop genetically enhanced populations and lines from GEM and other breeding crosses:

Two important factors influencing the successful development of enhanced populations are the choice of germplasm and the proportion of exotic material comprising the breeding cross.  GEM research addresses both of these questions. Wellhausen (1978) emphasized that the majority of maize races are non-productive, and stressed that breeders should focus on the four most productive racial complexes which include Tuxpeño (and its related Caribbean dents, and US dents), Cuban Flint, Coastal Tropical Flint, and ETO.  Goodman and Brown (1988) cite the same races, but expand upon it to include Cuban flint-cateto, Chandelle, Haitian Yellow, Tusón, and Suwan 1 and 2 (Thailand).  The most important tropical sources preferred by Goodman (1999) are commercial hybrids or public inbreds, due to less likelihood of inbreeding depression.  The proportion of exotic parentage appropriate for use in the breeding cross has been discussed throughout the literature, but there is not a substantial amount of empirical data.  Goodman (1999) emphasized that the appropriate effort in Raleigh, NC for GEM development is with 50% tropical breeding crosses.  Albrecht and Dudley (1987) concluded that 25% was the preferred starting material, which is in agreement with Wellhausen (1965), and Hoffbeck, et al. (1995).  All of the latter work was done in midwestern environments.  Opinion about the importance of random intermating is also changing.   Earlier breeders made adapted x exotic crosses and followed with several generations of random mating to break unfavorable linkages. More recent research suggest that random mating also breaks up favorable epistatic interactions, and there is more emphasis given to selection directly from crosses without random mating (Hoffbeck et al. 1995; Lamkey et al 1995).  This research supports changes to modern breeding practices; GEM protocol does not call for random mating of breeding crosses prior to selection.

Several researchers have proposed methods to select germplasm for breeding based on prediction formulae. Kraja and Dudley (2000) concluded from an evaluation study of GEM accessions that Dudley’s method (Dudley, 1987) of identifying favorable alleles for yield may not be useful when the gene frequencies of favorable alleles are low. The basis of their conclusion was that no yield improvement was found when the target hybrid was FR1064xLH185, a popular commercial hybrid in the Midwest.  However, in a companion study for multiple disease resistance, GEM accessions were identified having favorable dominant alleles for disease resistance not found in either parent of the target hybrid, FR1064xLH185 (Kraja et al. 2000).  Melchinger (1998) found that prediction of means and genetic variances in segregating generations could help assess the breeding potential of the base populations.  Using European germplasm they found that test cross means of the parental breeding crosses could be used as a predictor of test cross means of the F3 progeny. GEM’s original protocol was to test all breeding crosses by crossing with stiff stalk (SS) or non-stiff stalk (NSS) inbreds.  The highest performing breeding crosses in yield trials were given priority attention for development.  Once promising accessions were identified, the practice of yield testing breeding crosses was discontinued as a standard practice.  The results of the Salhuana et al. (1998) evaluation of performance of temperate accessions when crossed to SS and NSS testers were particularly interesting.  The accession x tester hybrids were evaluated in Argentina, Chile, Uruguay, and the USA and ranked for mean performance across all regions.  The best accessions identified included URZM10001, ARZM16026, and URZM11002 when crossed to stiff stalk testers, and ARZM16035, URZM13085, and URZM11003 when crossed to non-stiff stalk testers. The authors concluded that these accessions would be good sources for yield enhancement.  GEM trials from 1999-2002 confirmed all but two of these accessions as valuable sources for yield enhancement. 

Heterotic pattern identity influences the choice of tester lines and is not simply addressed with exotic germplasm.  The advent of molecular marker technology has made it possible to group germplasm into a larger number of sub-groups particularly with tropical material (Gethi et al. 2002; Reif et al. 2003).  U.S. breeders normally classify material as SS  or NSS, but further subdivision is possible into additional groups derived from crosses between the major groups, between adapted x exotic, or distantly related material such as Minnesota 13 (Gethi et al. 2002).  Eberhart et al. (1995) indicated that heterotic pattern identification is the key factor to maximizing performance, and suggested that breeders use common heterotic patterns to make exchange and evaluation meaningful.  GEM makes an effort to encourage international cooperators to identify their proprietary materials into SS and NSS groups in order to facilitate further development and testing of GEM breeding crosses.   Abel and Pollak (1991) emphasized the importance of the tester used in a study that demonstrated differences in performance rankings, and on the amount of root lodging observed in test crosses.  GEM-Ames currently uses commercial inbred tester lines provided by our private GEM cooperators to evaluate S2’s. This provides a comparable benchmark of performance of GEM derived lines with commercial hybrids.   Unfortunately, the NC location cannot use inbred testers in the southern environment due to poor pollen shed, therefore single cross commercial testers are used first, followed by separate testing of the best lines with both SS and NSS testers (Tallury and Goodman, 2001). 

Breeding methods for adapting exotic germplasm usually fall into two generalized categories - mass selection, and the multi-stage evaluation procedure used by the LAMP/GEM and NC programs (Tallury and Goodman, 2001).  Mass selection is a gradual introgression of germplasm into adapted material and was used by Troyer and Brown (1972) to introduce favorable alleles from Mexican material into Corn Belt germplasm over a 10 year selection period.  Hallauer (1994) used mass selection effectively for the development of populations BS28 (Tuxpeno), and BS29 (Suwan 1) adapted to Iowa.  Mass selection has been very effective for selecting against photoperiod sensitivity, silk delay, smut, and other deleterious traits. An excellent overview of the multi-stage breeding process using an alternate winter and summer nursery is provided by Holland et al. (1996).

Once exotic germplasm is adapted or “semi-adapted,” to the US, standard breeding procedures can be followed. Hallauer (1978) emphasized recurrent selection as a procedural follow-up to mass selection.  Eberhart et al. (1995) discuss several recurrent selection procedures including modified ear-to-row, full-sib family, S1 or S2 selection per se, and the pedigree method.  While each of these methods can be discussed at length, the salient feature emphasized by the authors is that the selection process should include strong visual selection for reduced anthesis-silking interval (ASI), and evaluations under high plant density to maximize genetic gain.  

The pedigree method was adopted by GEM as recommended by the TSG, and is discussed in detail under the objectives. As the most widely used procedure for commercial plant breeding in the U.S., it is expected to continue in popularity in the future (Hallauer, 1988). Molecular marker technology is expanding our options for plant breeding and providing new opportunities.  The classic procedure by Tanksley and Nelson (1996) of advanced backcross quantitative trait loci (QTL) analysis and transfer of genes from unadapted tomato may have wide applicability to other crops such as maize.  Recently, Ho et al. (2002) applied the technique to maize and transferred 4 grain yield QTL’s which had a phenotypic effect of 11% and 6.7% yield gain at two locations.

Evaluate genotypes in the breeding program for yield, agronomic traits, biotic and abiotic stress (including mycotoxins), and VAT’S:

The stability of yield across environments is very dependent on abiotic and biotic stress factors (Eberhart et al., 1995).  The most important abiotic stresses include heat and drought tolerance.  Both are physiologically complex and involve various mechanisms.  Extensive breeding and selection research by Edmeades et al. (1999) concluded that reduced ASI is an important attribute for selection, and is correlated with barrenness and drought tolerance.  Other phenotypic factors associated with drought resistance were stay green and reduced tassel size.  Perhaps the two most important findings were the necessity to utilize drought stressed environments to reliably identify drought resistance, and that genotypes that performed well under drought stress often performed favorably in non-stress environments.  Genetic gains of 5% per year were also reported when using S1 recurrent selection.  Betran et al. (2003) in Texas reported similar findings,  that selection in drought stressed environments was effective for identifying and developing drought resistant germplasm, and that those genotypes performed favorably in non-stress environments.  Both researchers demonstrated the importance of tropical germplasm as a source for abiotic stress resistance.

Stress tolerance is frequently associated with mycotoxin accumulation (Betran et al. 2002; Campbell and White, 1995).  Aspergillus flavus produces the toxic carcinogen, aflatoxin.  Although some sources of aflatoxin resistance have been identified, most of the available germplasm is too late or non-adapted to the Midwest.  USDA-ARS researchers Williams and Windham (2001) released the inbred Mp715 (derived from Tuxpan) as a source of aflatoxin resistance.   Betran et al. (2002) reported in a diallel study that the most resistant yellow hybrids included FR2128 x Mp715, Tx772xMp715, and Tx772xCML326.  Resistance was correlated with the primary trait, ear rot, as well as husk cover, kernel texture, poor ASI, and insect damage from corn ear worm, and fall armyworm.  Campbell and White (1995)  reported that Aspergillus ear rot ratings and aflatoxin accumulation were weakly associated (r=0.35 to 0.49) across the whole range of ear infection, but generally low levels of ear rot infection (ratings below 4.0) were indicative of aflatoxin levels less than 300ng/g.  The authors suggested that as a cost saving measure, breeders should visually screen ear rot on F2 plants initially, and analyze aflatoxin content in subsequent generations with appropriate ELISA test, etc.  Naidoo et al. (2002) conducted a diallel analysis and found highly significant GCA effects for ear rot and aflatoxin levels. The most promising sources were Tex6 and Oh516.  Future research will determine if the two inbreds share common resistance genes.  

Fumonisins are a family of mycotoxins produced by Fusarium verticillioides and F. subglutinans.  Current FDA Guidance levels are between 2-4 micrograms/gr of grain.  Since levels often exceed 5 micrograms/gr, the US grain crop is sometimes impacted although Federal guidelines are not yet in place (Clements et al. 2003).  Fusarium infection and fumonisin production are highly influenced by the presence of ear feeding insects such as the European corn borer, or corn ear worm which commonly carry spores of the fungus throughout the maize plant.  Preliminary screening in Illinois reported that ear rot ratings due to Fusarium were positively correlated (r=0.83) with fumonisin concentration (Clements et al. 2002).  This suggests that breeding for fumonisin resistance may be more successful than breeding for aflatoxin resistance.

Reports of resistance to corn insects found in exotic germplasm are abundant in the literature.  Abel et al. (2001) identified the first GEM source of non-DIMBOA resistance to the European corn borer; this was released as GEMS-0001. Research on the corn root worm (Hibbard et al. 1999), identified exotic sources of germplasm with levels of resistance equivalent to the chemically treated check. Differences in levels of resistance to corn root worm among GEM breeding crosses was reported by Hibbard for studies in 1999-2001 (GEM web site, Public Cooperator Reports). Southern rust caused by Puccinia polysora is an important southern pathogen in the U.S., Brazil, and other regions of the world   Resistant tropical sources have been identified and reported by Holland et al. (1998).  Some of these accessions are being used in a collaborative effort with GEM Ames, Raleigh, and Pioneer Hi-Bred to assemble germplasm differentials for screening trials, and to monitor and learn more about the pathogen racial variability.

Exotic germplasm has been found to be an important source of genetic variability for many VAT’s, including the quantity and quality of starch, oil, and protein (Pollak, 2003).  Jellum (1967) evaluated 1,850 foreign accessions for oil content and quality and reported very wide variability for all the major fatty acids.  Palmitic acid (16:0) ranged from 6-22%; stearic (18:0) ranged from 0.6-15%; oleic (18:1) from 14-64%; and linoleic (18:2) from 19-71%.  The range of variability is limited in Corn Belt lines.  Improvement for fatty acid modification should be feasible by selection (Lambert, 2001).  Fergason (2001) reported limited variability for amylose modifier genes in Corn Belt germplasm.   Research on amylose modifiers is of particular interest since amylose modifiers were identified in a GEM breeding cross with a Guatemalan accession by Dr. Mark Campbell.  There is also a lack of variability in domestic U.S. sources of waxy starch used for commercial breeding (Fergason, 2001), with improvements confined primarily to backcross conversions of existing cornbelt germplasm.  Exotic germplasm is also a source of diversity for the starch synthesis pathway - a key factor for yield.  Research on the maize starch pathway found that approximately two thirds of the genes in the starch pathway of U.S. maize germplasm had little diversity, while maize relatives Tripsacum and teosinte had more allelic diversity (Whitt et al.2002). This supports the premise that the allelic diversity found in exotic germplasm and wild relatives can be tapped for greater efficiency of maize starch synthesis and possibly yield.

Corn is the major source of starch produced worldwide and comprises 95% of starch manufactured in the U.S. (White, 2001). Germplasm from the GEM project was found to be a valuable source of starch with unique characteristics for thermal properties and starch granule structure (Ji et al. 2003).  Researchers found that the amylopectin from GEM sources had different branch chain distribution; other sources had two types of starch granules with unique gelatinization peaks.  Singh et al. (2001) reported differences in paste and gel behaviors from several GEM accessions but believed the differences were not substantially different enough from commercial sources to be of immediate value to the starch industry.  However, a recurrent selection program was recommended to enhance starch quality of the better accessions. Ji et al. (2002) reported that genotype x environment interaction was a factor in starch thermal properties during 3 successive years in the same environment.  The same study reported fixation of starch thermal properties in some lines derived from GEM and was encouraging.  No reports were found in the literature for reciprocal differences among crosses for starch thermal properties; a study is in progress to determine the effects of maternal inheritance and will be discussed under objective 3.

The advent of molecular marker technology and plant genomics will open new opportunities for GEM germplasm research.  Projects of interest include identifying the contribution of alleles from the exotic source and their impact on phenotypic expression and overall performance.  Ragot et al. (1995) reported that 17% of 70 maize alleles identified from exotic origins were favorable for yield enhancement.  As genes from exotic sources become introgressed into adapted germplasm several key agronomic questions arise - effects on yield stability, impact on phenotypic effects, and heritability.  These questions require close interaction with plant breeders and genomics groups.  Kresovich et al. (2002) emphasized the importance of “molecular characterization,” in addition to phenotypic characterization used by plant breeders and germplasm curators.  Allelic diversity studies may identify differences between agronomically elite lines and non-elite sister lines.  Technologies such as association analysis will help link information on DNA polymorphism to phenotypic characterization. (Remington et al., 2001).


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The GEM Project works closely with the NCRPIS’ Program for Conservation, Management, Enhancement, and Utilization of Plant Genetic Resources (CSREES IOW01018).  All population accessions used by the GEM Project are maintained and freely distributed.   New releases from the project are assigned Plant Introduction (PI) designations, and maintained and distributed through the NCRPIS maize curator, Mark Millard.  Collaboration with Linda Pollak (USDA-ARS, Ames) includes providing germplasm and technical information to meet the objectives of the new CRIS 3625-21000-040-00D, Breeding High Quality Corn for Sustainable, Low-Input Farming Systems.

GEM researchers at Ames collaborate closely with Major Goodman (NC State), and Joe Hudyncia (USDA-ARS) in Raleigh, NC. The Raleigh site provides a unique southeastern U.S. testing environment, from which a broad range of lines are derived from 100% and 50% tropical germplasm through GEM support and CSREES NC06634.  Collaborative research with USDA-ARS geneticist Jim Holland, and NC State Geneticist Major Goodman is in progress for Fusarium resistance, fumonisin evaluation, and genetic mapping of GEM germplasm (CRIS 6645-21000-021-01S).  Collaborative research with Michael Clements and Paul Williams (USDA-ARS based at Mississippi State, CRIS 6406-21000-009-02T) includes evaluation of GEM breeding crosses and S3 lines for resistance to ear mold and aflatoxin production.   European corn borer resistance and other insects are being studied by Craig Abel (USDA-ARS, Stoneville, MS) for various selected GEM lines (CRIS 6402-22000-034-00D).  A collaborative research project with David Willmot and Larry Darrah of USDA-ARS in Columbia, Mo, (CRIS 3622-21000-016-00D) includes QTL analysis for yield and other traits in a very important GEM accession, CUBA164.  Willmot and Bruce Hibbard (USDA-ARS, Columbia, MO) are research collaborators for evaluation and breeding research of GEM germplasm for Western Corn Root Worm resistance. 


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Approach and Research Procedures

Objective 1: Coordinate the GEM Project by managing an extensive multi-site cooperative breeding program and information sharing with public and private cooperators.

Hypothesis: Broadening the germplasm base requires the cooperative effort of private and public collaborators to provide genetic resources, sufficient yield testing environments, expertise and facilities for germplasm evaluation, and data management technology to facilitate information exchange.

Summary:  Evaluate research requirements for nursery, trials, and lab analyses, and arrange for in-kind support.  Manage germplasm curation, including regeneration, storage, inventory, and transfer of germplasm.  Serve as the liaison for the GEM TSG and the GEM Cooperators to foster effective interaction, arrange for in kind support, and technology transfer (research information sharing and germplasm exchange).   Coordinate effective interaction with the Raleigh, NC GEM personnel for germplasm exchange, evaluation, and information sharing.  Serve as the Authorized Departmental’s Officer’s Designated Representative (ADODR) for Specific Cooperator Agreements (SCA), facilitate procedures for reporting results, and summarize information.  Expand the scope and volume of GEM data and computer network management activities.

Methods: A key priority of GEM is to coordinate the necessary in kind support to effectively meet the requirements of GEM S2 and S3 topcrosses, and the nursery support needed to provide germplasm for testing. The coordinator functions by organizing the yield trial program, testing environments, and identifying and working with trial cooperators.  Data are returned to the coordinator and analyzed at the conclusion of the harvest season and results are prepared for presentation at the Annual GEM Cooperator’s Meeting held during the American Seed Association (ASTA) in Chicago in December.

In kind support nursery and disease observations are arranged in a similar manner as the yield trial program.   Each cooperator agrees upon a pre-arranged level of in kind support but the choice of germplasm and breeding generation provided (make S1, S2, new crosses, etc) is made by the Coordinator and driven by GEM project needs. An effort is made to work closely with each cooperator to identify trial and nursery environments, maturity zone, and the biotic and abiotic stresses prevalent which offer potential for evaluation.  This information is used for assigning pedigrees to regions for evaluation and/or development.  (Procedures used to select germplasm for development are discussed under objective 2.)

The Coordinator is responsible for managing the inventory and life cycle of GEM germplasm.  This includes seed preparation, regeneration, cold storage, inventory management, and distribution (technology transfer). Seed storage is in a new 10,000 square foot cold storage facility at the NCRPIS. Day-to-day-management of GEM germplasm is provided by the GEM Technician, Mr. Brian Alt.

Effective guidance and interaction among GEM TSG members impacts program direction.  The TSG consists of seven members from the maize industry, one public member, and three ex- officio representatives from the USDA-ARS including the Coordinator.  Collectively, the TSG represents more than 200 years of corn breeding experience with several members having extensive knowledge in tropical germplasm and breeding.  Industry representation consists of membership from large, medium, and small companies with rotating membership terms of 3 years.  Meetings with the GEM TSG are held three times per year to review results and procedures, evaluate and discuss germplasm, and finalize plans for each new cycle.

Research targets considered to be “priority traits” are defined by the GEM TSG and reviewed annually. During the March, 2003 TSG meeting the most important targets identified included the abiotic traits of heat and drought stress; resistance to biotic stresses with focus on anthracnose, grey leafspot, and corn root worm; resistance to the major mycotoxins, aflatoxin and fumonisin; and VAT’s such as grain quantity and quality of starch, protein, oil, including silage quantity and quality.  The importance of agronomic traits such as yield, lodging, rapid dry-down, and high yield/moisture ratio is paramount and cannot be assumed.   The VAT targets include protein content at 13%, oil content >6%, and starch content of 75% (Pollak, 2003).  Since corn protein is known for its lower quality due to prolamines found in zein, emphasis is given to identifying germplasm with above average content of amino acids such as lysine, tryptophan, and methionine.  For fatty acids (oil), focus is on identifying germplasm with extremes for saturated fatty acid content (above 30, or below 6%); and oleic content >65%, and ideally =80%.  Starch quality parameters were defined by Pollak (2003) as thermal properties which are predictive for the functionality of starch for food or industrial applications, and determined by the differential scanning calorimeter (DSC).   

Raleigh, North Carolina is another site of GEM germplasm activities, and is under the leadership of the USDA-ARS southeastern Coordinator, Joe Hudyncia, working closely with Dr. Major Goodman.  Mr. Hudyncia has an MS degree in plant pathology from NC State and is responsible for nursery and testing programs for the southeastern US.  The focus of Raleigh’s GEM effort is line development from 50% tropical breeding crosses.  The rationale for the focus on 50% tropical germplasm (as opposed to 25%) is greater genetic diversity, and higher levels of disease resistance may be attained (Goodman, 1999). The late maturity environment of Raleigh is conducive to working late 50% tropical breeding crosses. Important diseases prevalent in Raleigh include grey leafspot, southern rust, and Fusarium ear rot.  There is an important gap in our knowledge about the utility of lines developed in Raleigh for Midwest breeding programs.  Midwest breeders are usually reluctant to use material from the southern regions due to late maturity and lack of adaptation to the Midwest.  GEM-Ames evaluates the Raleigh lines in the Midwest as lines per se and in hybrid combination with common commercial check lines used in the Ames yield trials.  Release notices will be prepared and submitted to Crop Science after the 2003 yield trial data are analyzed and coding decisions are completed.

SCA’s are an important aspect of the GEM Project and serve as a means to provide technical expertise, facilities, and/or testing sites to help GEM meet its objectives. The Coordinator, as ADODR for the GEM SCA’s, functions by representing the Authorized Designated Officer (ADO) in the administration and supervision of the agreements.  Interactions with the SCA Principal Investigators and the Coordinator include choice of germplasm, methodology, and discussion of preliminary data results.  Progress reports of each SCA project are done annually in July/August, and presented by the Principal Investigator each December at the GEM Cooperator Meeting. Project proposals for funding are evaluated by the coordinator and recommendations are made to the GEM TSG.  Funding decisions are based on relative project importance with preference given to priority targets, feasibility, justification for resources needed, and facilities and expertise of the Principle Investigator.  SCA Projects funded in 2003 and their research targets (maybe be multiple) are summarized in Table 1.  

Information sharing is an important aspect of technology transfer and drives the successful utilization of our germplasm.  The coordination effort includes expanding the scope and volume of GEM data and computer network activities such as implementing the relational database Plant Research Information Manager (PRISM).  Planned PRISM enhancements include linking pedigrees to traits (VAT’S, disease, yield, etc.), and management of nursery and collaborator assignments, seed inventories, and shipping records.  Bar coding of germplasm will also be implemented following the priority enhancements. GEM maintains an active web site at ( to share information for yield, VAT’s, and announcements of new germplasm releases for GEM Cooperators and to the general public.   Trial results are posted to the website after being reviewed.  The web site includes1999-2002 yield data; 1996-1998 data is available on CD ROM.  VAT data will appear on the web beginning in 2003-2004.  Presently, VAT summaries are given in the GEM Annual Reports (also on the GEM website) for the pedigrees having the highest values for percent starch, oil, and protein based on near infrared reflectance spectroscopy (NIRS) data.  Starch quality data based on starch thermal properties from differential scanning calorimetry (DSC) will be posted in 2004.

Summarizing, GEM’s policy is to share all research results openly to maximize knowledge for germplasm performance, utilization, and breeding methods.  GEM private Cooperators conducting in-kind yield trial support provide data directly to the IT Specialist in Ames via e-mail on Excel spreadsheets.  Reports from Public Cooperators (SCA reports) are sent directly to the GEM Coordinator.  Following review and revision (if necessary), the data is shared with the GEM TSG, and then made available to all the GEM Cooperators. The two major vehicles for sharing research results is the GEM web site, and the Annual Cooperator’s meeting in Chicago held in conjunction with the ASTA meeting in December.  All of the results presented in the December Meeting are included on the web site that is updated annually in January, and at various times throughout the year as needed.   To facilitate “user friendliness,” a section entitled “what’s new” on the GEM website includes all the year’s most recent data and reports.  Results from past year’s research can also be found by searching the respective year of interest.  Currently GEM results on the web include: Yield Trial Data from the Midwest and southern region trials coordinated from Raleigh. This includes S2 topcrosses, and second year S3 topcrosses.  Public Cooperator Reports (all SCA reports from 1996-2003), and the GEM Annual Report ( 2-year recommendations,  protocol/policy revisions recommended by the TSG, lab data summaries, new GEM Cooperators, etc.).  Hard copies of all reports are distributed at Chicago and are available upon request.  The most recent addition to the GEM website is a section entitled “Public Cooperator’s Contributions” citing the name, institution, year, and study area.  This facilitates search for specific SCA project reports by subject such as root worm, VAT, silage, etc   The Coordinator and IT Specialist also provide additional data on a per request basis for information not readily available via the web.  This includes miscellaneous notes such as nursery observations, disease notes, and additional data such as VAT’s not covered in Annual Report summaries or lab reports.  Dr. Major Goodman also provides similar information upon request for southern regions.  

GEM Staff: The USDA-ARS GEM Technician, Brian Alt, joined GEM in July 2002 and has a background in soybean and corn breeding with an MS from Iowa State.  Mr. Alt is responsible for handling most of the technical aspects of seed curation and seed shipping, and is an important part.  He is also an important part of the management of pollination nurseries and yield trial sites. Data management is the responsibility of USDA-ARS Information Technology Specialist, Nuo Shen.  Dr. Shen officially joined GEM in March 2003, but served as GEM’s Acting Database Manager while working as a post doc for corn oil research for USDA-ARS Research Geneticist, Dr. Linda Pollak.  Dr. Shen has a Ph.D. in Food Science from Iowa State University, and a background in statistics and data management. Sue Duvick is the USDA-ARS Quality Traits Lab Manager. Ms. Duvick has been involved with quality traits research since 1991.

Collaborators:  Private industry GEM Cooperators conducting trials and nursery support- David Bubeck, Pioneer Hi-Bred International, Inc.; Mike Graham, Monsanto Company; Randy Holley, Syngenta Seeds, Inc; Jim Deutsch, Garst Seed Co; Joel Holthaus, Holden’s Foundation Seed, L.L.C.; Duane Potrezba, NC+ Hybrids; Jerry Rice, Mycogen Seeds; Kevin Montgomery, Golden Harvest Seeds, Inc; Freeman Whitehead, AgReliant Genetics, L.L.C.; Kevitt Brown, FFR Cooperative; Roger Levy, Beck’s Superior Hybrids, Inc; Tom Hoegemeyer, Hoegemeyer Hybrids Inc.; Bill Forgey, Pau Seeds, Inc.; Dave Deutscher, Illinois Foundation Seed, Inc.; John Schillinger, Schillinger Seeds; David Benson, Benson Seed Research L.L.C.; Brad Ostrander, National Starch and Chemical Co.; Robert Hughes, SEEDirect; Jim Dodd, Professional Seed Research, Inc.

SCA’s and Public Cooperators- Javier Betran, Wenwei Xu, Texas A&M; Martin Bohn, U of IL; Mark Campbell, Truman State University; Marcelo Carena, U of ND; Jim Coors, U of WI; Jim Hawk, U of DE; Manjit Kang, LSU; Rich Pratt, Ohio State; Margaret Smith, Cornell; Dennis West, U of TN; Ken Russell, U of NE; Major Goodman, NC State; Ken Ziegler, Kendall Lamkey, Arnel Hallauer, Mark Westgate, Pamela White, Susana Goggi, and Jay-Lin Jane, ISU.  SCA projects can be found in Table 1.

Non-governmental organizations- Walter Goldstein, Michael Fields Agricultural Institute, evaluates GEM breeding crosses for sustainable agriculture applications, including weed competitiveness and yield.

USDA-ARS-Jim Holland conducts Fusarium/fumonisin evaluations of GEM breeding crosses and lines in Raleigh; Craig Abel evaluates GEM material for insect resistance in MS; Larry Darrah and David Willmot conduct QTL analysis of yield factors in CUBA164 with Ames and other collaborators; Bruce Hibbard and Willmot are conducting a corn root worm molecular breeding project in Missouri; Michael Clements and Paul Williams evaluate GEM germplasm for aflatoxin in MS; Paul Scott in Ames evaluates germplasm for amino acid content with focus on lysine, methionine, and tryptophan;  Linda Pollak investigates applicability to sustainable agriculture systems, and quality trait research.

International Collaborators- Empresa Brasileira de Pesquisa, Agropecuaria (EMBRAPA); Brazil; - Instituto Nacioanal de Tecnologia Agropecuaria (INTA) Argentina; Nidera, and Sursem S.A., Argentina; Maharlika Genetics, Mexico; AgriSource Co., Ltd., Thailand; Hyland Seeds, and the U of Guelph; Canada.  All provides germplasm by making breeding crosses and conducts breeding and/or disease evaluations such as Mal de Rio Cuarto (Argentina), and downy mildew (Thailand), etc.

The collaborator network for data management includes Greg Van Holland (owner of PRISM), and a team from Ames including USDA-ARS maize researchers Paul Scott, Sue Duvick, Linda Pollak, Candice Gardner, Mike Blanco, and ISU Agronomy Professor, Kendall Lamkey.  The team regularly reviews database design needs, and implementation plans.  Dr.  Lamkey’s extensive experience with PRISM is a key asset.

Contingencies:  In kind support efforts will be reevaluated and potentially re-assigned to other cooperators in the event that some cooperators reduce support of programs contributing to the GEM Project’s objectives.  In the event PRISM does not serve GEM’s requirement, a modification of PRISM will be implemented, or alternative software will be investigated.


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Table 1. GEM SCA's and USDA-ARS Projects Supporting GEM's Objectives




Yield / Agrono-mics

Stress Tole-rance

Quality Traits


Stalk Rot Res

Other Dis

Root Worm

Other Insect

Silage Quality

Javier Betran

Texas A&M

Aflatoxin evaluation of GEM advanced lines with different fatty acid content







Martin Bohn

U of I

Evaluation of Advanced GEM Lines for Multiple Insect Resistance and Fumonisin Concentration








Mark Campbell

Truman State U

Combining GEM Lines for the Development of Amylomaize VII (>70% amylose) Germplasm with Increased Starch Content and Improved Yield Potential








Marcelo Carena


Early GEM: Incorporating GEM elite lines in early maize









James Coors

U of WI

Development of Inbreds, Hybrids, and Enhanced GEM Breeding Populations with Superior Silage Yield and Nutritional Value







James Hawk


Inbred Line Development and Hybrid Evaluation in GEM Breeding Crosses







Manjit Kang


Identifying Resistance to Infection by Aspergillus flavus and Fusarium in GEM Breeding Crosses and Advanced Breeding Lines









Richard Pratt


Optimization of Protein and Oil Value-Added Traits and their Combination with Elite Ames and Southern GEM Lines








Margaret Smith


Anthracnose Stalk Rot Resistance from Exotic Maize Germplasm








Wenwei Xu

Texas A&M

Characterization and Use of GEM Breeding Crosses for Drought Tolerance, Grain Mold Resistance and Corn Earworm Resistance






Dennis West


Breeding lines with exotic germplasm









Ken Russell


Selection for phosphorus concentration in maize grain







Hibbard & Willmot


Molecular Breeding for Corn Rootworm Resistance in Maize





















GLS = Grey Leaf Spot      ECB=European Corn Borer    CEW=Corn Ear Worm











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Objective 2:  Develop genetically advanced populations and inbred lines from GEM Project germplasm and other breeding crosses.

Hypothesis:  An effective approach to developing genetically advanced germplasm is the modified pedigree breeding method.  Developed lines will be evaluated as S2 and S3 topcrosses relative to the mean yields of five commercial check hybrids over a two year period.

Summary:  Manage and direct the breeding nursery at Ames by developing S3 lines from GEM breeding crosses with emphasis on the priority research and development (R&D) targets identified by the TSG (see objective 1).  Considerations include choice of germplasm, breeding procedures, and testing environments to meet the priority target goals.  Adhere to the GEM protocol for developing S3 lines from GEM breeding crosses that involve LAMP accessions crossed with the proprietary lines from GEM private Cooperators.  Advance and select the lines in the nursery in preparation for objective 3, evaluation.

Methods: The priority objectives of GEM Ames include the development of adaptable germplasm having VAT’s, with yield and agronomics competitive with commercial germplasm.  Germplasm developed in Ames feeds into other studies such as SCA projects for further selection and evaluation of other traits.  The central Iowa Ames location provides a suitable nursery site for the development of germplasm ranging from 105-118 days, and is very representative of the Midwest. Information and products developed here can be transferred to most regions of the central Corn Belt. Although disease pressure is seldom severe, levels of smut, grey leafspot, anthracnose, rust, and various leaf blights periodically occur at levels adequate for selection.  European corn borer, root worm, and aphids, are usually prevalent at selectable levels.

An important part of any breeding program is the choice of germplasm. The Ames program makes an effort to utilize 25% and 50% temperate breeding crosses, and 25% tropical breeding crosses for most developmental work.  The major focus is on 25% and 50% temperate (given equal attention as source material), followed by 25% tropical.  Only a few of the earliest 50% tropical breeding crosses are worked in Ames or the Midwest.  Individual breeding crosses selected for development in Ames (or to be assigned to Cooperators) are chosen by a combination of methods.  Breeding crosses are phenotypically evaluated per se for general adaptability in Ames, and at 2 additional locations provided by GEM Cooperators.  The most important traits are flowering date and photoperiod sensitivity, followed by root lodging, stalk lodging, ear and plant height.  Tassel sterility is not uncommon in breeding crosses and breeding crosses with a high percentage of sterility are eliminated.  Breeding crosses that are satisfactory in all three locations are reported, reviewed by TSG and Raleigh group, and prioritized, using previous knowledge and experience based on the LAMP accession involved in the breeding cross.  The TSG Chairman, Dr. Wilfredo Salhuana, and Dr. Major Goodman, provide valued insight from years of experience with LAMP accessions and exotic germplasm. 

In addition to the phenotypic observations, choice of germplasm is based on research targets and knowledge of the material.  Previous data collected by the Quality Traits Lab on breeding crosses and lines derived from an accession with known attributes are particularly helpful.   For example the accession AR16035 is known for its high protein and oil; CUBA164 provides extreme values of starch thermal properties. Information from multi-year data and SCA Public Cooperator reports can be found on a multitude of traits such as yield, maturity, diseases, insects, aflatoxin, fumonisin, silage, grain quality, etc., and is extremely helpful in selecting germplasm for breeding.

The pedigree method is the procedure used to develop lines from GEM breeding crosses.  The decision to use this method and the associated selection protocols, sampling numbers, testers, etc., evolved over several years of TSG discussions and planning sessions.  It was decided that the pedigree method was a procedure all companies were familiar with and had a desirable rapid turnover time (Pollak, 2003).  A descriptive flow chart depicts the modified pedigree breeding protocol (Fig. 1) used by GEM, modified from the original (Pollak, 2003), and was adopted by the TSG in March, 2003.  Revisions include decreasing the number of plants sampled per breeding cross from 1,000 S1 selfs, and 200 top crosses tested, to 250-300 S1 selfs, and 50 S2 topcrosses tested per breeding cross.  Eberhart, stressed the importance of effective population size, and suggested that 160-400 S2 top crosses be evaluated from a population originating from 1,000-2,000 selfed S1 plants.  Although the importance of adequate sample size is recognized, the revision in protocol was based on three factors.  First, companies were reluctant to make 1,000 selfs in unadapted material, and more typically returned 300-500 selfed ears.   Second, the resources required to develop one breeding cross were extensive (projected relative costs are $7,000-8,000 from initial selfing through testing) and only 10-12 breeding crosses were being worked per year throughout the combined GEM and Cooperator nurseries.  Third, performance of S2 topcrosses from most breeding crosses (66%) were significantly below the mean of the 5 commercial checks and routine selfing was not justified on all breeding crosses, considering the resources required.   Selected breeding crosses are extensively re-sampled for those populations having good initial performance, providing better return on research investment.  Several breeding crosses such have already been resampled, including those with Cuba 164.

The GEM line development graphic (Appendix Table 1) illustrates the number of rows (or plots) required each year for nursery, isolations, and yield trials (YT) for one breeding cross.  It does not exactly parallel the generations of the flow chart (Fig. 1) since winter nursery isolations for Ames developed lines are seldom used due to resource allocation needs for priority selfing.  (Private companies often utilize winter nursery isolations for making GEM S2 topcrosses therefore their activity follows Fig. 1; Ames developed lines follow the development plan of Table 1).  Using Appendix Table 1 as an example for one breeding cross initiated in summer, and one initiated in winter, an Excel formula was developed to illustrate the number of nursery rows, isolation rows, and YT plots (1 plot=2 rows) required. Since S1’s can be made in winter or summer, working 1 breeding cross in winter and 1 in summer requires 50 rows for making S1 (20 seeds/row) in winter and summer nurseries; 500 S1 family rows for making S2 in summer (S2 can only be made in summer), 240 isolation rows, and 760 plots (50 entry x 6 locs for year 1; and 10 entries x 8 reps for year 2 for each of the two breeding crosses).  Appendix Table 2 summarizes the projected number of rows and plots required under different scenarios of numbers breeding crosses that need to be managed.  It was concluded that with available resources and in kind support, the GEM network (includes Ames and Midwest cooperators) can adequately manage 30 breeding crosses per year using winter and summer nurseries.

Collaborators:  See collaborators listed under objective 1.

Contingencies:  Time lines may be impacted in the event of crop failure, or due to lack of performance of chosen germplasm. The best available germplasm will be used until a better source is found. In the event of crop failure, alternative nurseries are expanded to accommodate needs.  If nursery resources become limited, alternative breeding strategies such as single seed descent (requires less resources) may be considered.  The data will be closely monitored to determine if initial sampling numbers adequately reflect breeding potential of breeding crosses.


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Objective 3:  Evaluate genotypes in the breeding program for yield, agronomic traits, biotic and abiotic stress (including mycotoxins), and value-added traits (VAT).

Hypothesis:  Genotypes will be evaluated for yield, agronomic traits, biotic and abiotic stress including mycotoxins, and value-added traits.  The objective of the Ames evaluation will focus on yield, agronomic and value-added traits; SCA collaborations support the objectives by focusing on specific priority traits such as aflatoxin, rootworm resistance, silage, etc.

Summary:  Conduct “in house” yield trials at Ames, Raleigh, and outlying locations managed by each GEM site.  According to the standard protocol, genotypes are evaluated for yield as S2 top crosses prior to initiating laboratory evaluation for VAT’s.  Ten percent of the S2 lines in topcross yield trials are chosen based on agronomic performance for further laboratory evaluation of VAT’s.  Some genotypes are further evaluated for starch composition and/or lysine, methionine, and tryptophan content.   The protocol of evaluating yield first is not necessarily followed in certain experiments focused on traits such as root worm resistance, aflatoxin, and material with unique specialty traits; the frequency of desirable alleles for these traits may be rare. 

Methods:  Meeting GEM’s objective for the evaluation of germplasm for priority targets requires the support of GEM-Raleigh, the private Cooperator trial network, and a network of public cooperators having the required expertise, facilities, and environments for adequate evaluation. New breeding crosses are made only by GEM’s private Cooperator network since proprietary germplasm is used.  Although GEM has no control of the proprietary material used, elite inbreds used in commercial hybrid production is the standard practice when making GEM breeding crosses.  Generally, companies use germplasm from previous generation hybrids (one generation removed from new released hybrids).  To maximize GEM’s probability of success, new breeding crosses are made every year to capitalize on the newest germplasm available.

It is imperative that a system of accountability and understanding be in place to assure that research results and germplasm are available and freely shared among GEM Cooperators.  Cooperators agree to freely share germplasm and data by adhering to the terms of a “Proprietary Material Contributors Agreement,” signed upon joining GEM.  In addition, Cooperators agree to provide in-kind support according to the GEM protocol for nursery, trials, disease/insect evaluations, VAT’s, etc.  The type and level of in-kind support is documented annually via an Appendix that includes the statement, “It is understood that any seed or data generated as defined in this appendix is considered in-kind support and shall be returned to the GEM Coordinator.  Such seed and/or data shall be shared with other GEM Cooperators, who shall have the right to freely use such seed or data.”  To further encourage the utilization of GEM germplasm among Cooperators, recommendations are made each year based on two years of trial performance data.  The S3 lines (involved in recommended topcross data) are made available on a per request basis to Cooperators.

The program at Ames serves as a “general model” for the evaluation of most priority traits.  S2 topcrosses are initially evaluated for yield using 1 commercial inbred tester.  Testing at the S2 stage is considered early testing (Fehr, 1987).  Goodman (1999) emphasized the importance of early testing, particularly for exotic material to maximize the additive genetic variation contributed by the exotic accession.  Yield trials are planted as randomized complete block designs (RCBD) at 6 locations, using 1 rep per location.  The basis for agronomic performance is comparison of the GEM lines to the mean of 5 commercial checks.  Generally, the VAT’s are measured by NIRS analysis only on the top performing S3 lines (upper 10%) from the yield trials.  It would be too costly and labor intensive to do NIRS on all genotypes. NIRS is a non-destructive method and requires approximately 250 grams of seed.  Seed is harvested as a bulk sample from approximately 8 selfed ears per row. In addition to NIRS analysis, the top 10% of GEM entries in the trials also are analyzed for starch thermal properties by DSC. The DSC method is a destructive technique, but requires 5 seeds.  Samples for DSC analysis are taken from a single S3 ear.  Public release and subsequent registration in Crop Science requires a second year of yield testing on 2 inbred testers at 8 locations (see Fig. 1), and lab quality analysis.  Flexibility is desirable until more is known about the interrelationship of the traits with agronomic performance desired.  Consistent performance for yield and VAT traits over 2 years is the one prerequisite for release at this time.

A starch quality experiment is being conducted by the Ames Coordinator and lab traits manager, Sue Duvick.  In 2002 nursery, lines were identified with extreme values of various starch thermal properties including 5 traits: peak temperature onset of gelatinization, range of gelatinaztion, enthalpy of retrogradation, percent retrogradation, and the peak height index of the thermogram.  Although GEM lines have been identified having extreme values for starch thermal properties (Pollak, 2003), information is limited on the consistency of these traits over years, or if trait heritability is sufficient to warrant efforts to enhance the levels of the extreme values. To study this,  crosses are needed among lines with high values (HxH), or low (LxL), and high crossed to low (HxL).  Approximately 20 within heterotic group crosses were made reciprocally (40 total) in summer 2003 of lines having extreme values.  The F1’s (F2 seed) will be analyzed to determine any reciprocal differences, the F2’s will be selfed in winter nursery, and F3’s will be planted in 2004 summer to determine if transgressive segregants can be found with extreme values.  This germplasm can serve as a source of germplasm for enhancement of starch quality, and provide preliminary information for other genetic studies.

Evaluating a line as an S2 top cross prior to initiating selection for other traits is not practical for traits, if the corresponding gene frequencies for the trait phenotype are low in the gene pool.  Aflatoxin resistance would be an example.   Li et al. (2002) evaluated 61 GEM breeding crosses for per cent ear rot infection for the two years 1995-1996.  Mean percent kernel infection ranged from 48% to 11%, with LSD 0.05=12.71.  Some of the best breeding crosses included accessions from Argentina and Uruguay.  Breeding crosses and respective progeny are being evaluated in 2003 for ear rot and aflatoxin content by Dr. Manjit Kang in Louisiana, and USDA-ARS researcher Michael Clements, in MS.

Xu and Blanco (2003) reported that breeding crosses that have resistance to drought, corn earworm, and grain mold are good sources for developing lines for similar attributes of abiotic stress resistance.  Lines were selected and developed under the same stress regime as the parental breeding crosses.  Breeding crosses were evaluated since 1999, and lines were extracted from the most resistant crosses and tested in yield trials with promising results.  Testing in 2003 also includes Elisa testing for aflatoxin.   Lines for stress tolerance, corn ear worm, and grain mold resistance are scheduled for release in fall, 2003.

Collaborators:  See collaborators under objective 1.  See Table 1 for list of SCA project titles.

Contingencies:   Newer methods for non-destructive analytical measurement (i.e., quantifying amino acid content) are in various stages of development and must be validated versus accepted standard methods.  Consistency of VAT results will be analyzed using additional years of testing if required.  Success of disease and insect infestations will be monitored and inoculations or infestation repeated if necessary.  Projections for released lines from SCA projects may be contingent on future funding and continuation of projects.


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Personnel and Supplies:  Current GEM CRIS project funds support salary and benefits for 1 CAT IV, GS-14 SY; 1 Biological Science Lab Technician, GS-7; 1 Plant Biologist, GS-11; 1 Information Technology Specialist, GS-11; and 4 Federal Student Temporary Employees.

Facilities: GEM has offices, lab space, and cold seed storage facilities at the NCRPIS headquarters owned by the ISU Agricultural Experiment Station in Ames, and leased by the USDA-ARS. This site also provides access to a machine shop and maintenance facilities, and seed drying facilities.  The seed cold storage facility was built in 2002, and consists of 10,000 square feet of space to adequately provide storage and maintenance of GEM germplasm.  Land used for Ames nursery and yield trials is owned Iowa State University; the lab for quality traits analysis is located in ISU’s Agronomy Hall.  GEM has access to lab equipment for trait analysis that includes a Perstorp 6500 analytical grade near infrared spectrometer with sample transport module and natural product cell; Perkin-Elmer DSC7 differential scanning calorimeter, and a Hewett Packard gas chromatograph.  Field equipment includes a tractor, an Almaco Twin Plate II Precision Planter, and a Gleaner K combine that was donated by Pioneer Hi-Bred.




Increased exchange of information will ultimately result in greater knowledge of germplasm and its use for plant breeding programs.  Information transfer results from GEM Field Days, SCA Progress Reports, the GEM Cooperator meetings, and the web site.  Implementation of the PRISM database is projected by the fall of 2004 for agronomic traits, and for VAT’s in 2005.  A manuscript will be submitted for the GEM lines developed in Ames and Raleigh in early 2004.  New public releases are expected thereafter each year through 2007.  Greater knowledge will result  about the utilization of southern germplasm for Midwest breeding programs, the feasibility of 50% vs. 25% exotic germplasm for developmental breeding crosses, and the identification of the most useful sources of germplasm for agronomic and priority target traits.  The success of the GEM public/private collaboration will hopefully serve as a model for other crops.


It is projected that the change in breeding protocol (reduction of number of plants selfed and tested per population) will result in development and evaluation of 30 new breeding crosses per year in the GEM network.  A continuous effort is made to incorporate new proprietary germplasm from private cooperators; each company is requested to make new breeding crosses about every three years.  New sources of exotic germplasm are identified by searching germplasm databases such as GRIN, and making within heterotic group crosses among GEM S3 lines.  Greater knowledge of breeding methodology for enhancing exotic germplasm will result (particularly pertaining to the pedigree method), as well as identifying a priori the best germplasm for development.  Further information collected will document appropriate heterotic groupings, and reflect the multi-stage evaluation results of germplasm enhancement.


New products include S3 germplasm of agronomically useful material having VAT’s such as higher levels of starch, oil, and protein.  The primary source of this germplasm originates from GEM Ames and Raleigh, with yield evaluations made by GEM private and public cooperators.  Germplasm is projected for public release in 2004.  Starch quality germplasm having unique thermal properties from the Ames program is projected for release to GEM cooperators in early 2004, and for public release in 2005.  Products from SCA’s include germplasm for stress tolerance and yield in 2004/2005, a potentially high yielding source of anthracnose resistance, a source of germplasm for high amylose, and high yielding silage germplasm with nutritional quality. Release of corn root worm and mycotoxin resistant germplasm is projected for 2006/2007.  An early maturity source of aflatoxin resistance is a key objective. Greater knowledge will result from evaluation/analytical methodology such as biochemical analysis for amino acids (USDA-ARS collaboration with Paul Scott).  Also new knowledge will be available on QTL’s impacting yield from CUBA164 germplasm (USDA-ARS collaboration with Willmot and Darrah). 


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Abel, B.C. and L.M.  Pollak.  1991.  Rank comparisons of unadapted maize populations by testers and per se evaluation.  Crop Sci. 31:650-656.

Abel, C.A., L.M. Pollak, W. Salhuana, M.P. Widrlechner, and R.C.  Wilson.  2001.  Registration of GEMS-0001 maize germplasm resistant to leaf blade, leaf sheath, and collar feeding by European corn borer.  Crop Sci. 41:1651-1652.

Albrecht, B. and J.W. Dudley.  1987.  Evaluation of four maize populations of exotic germplasm.  Crop Sci. 27:480-486.

Betran, F.J., D. Beck, M. Banziger, and G.O. Edmeades.  2003. Genetic analysis of inbred and hybrid grain yield under stress and nonstress environments in tropical maize.  Crop Sci. 43:807-817.

Betran, F.J.,T. Isakeit, and G. Odvody.  2002. Aflatoxin accumulation of white and yellow maize inbreds in diallel crosses.  Crop Sci. 42:1894-1901.

Campbell, K.W. and D.G. White. 1995.  Inheritance of resistance to Aspergillus ear rot and aflatoxin in corn genotypes.  Phytopathology 85:886-896.

Clements, M.J.  2002.  Resistance to Fusarium ear rot and fumonisin in corn.  Proc. 38th Annual Illinois Corn Breeder’s School, p. 54-65.

Clements, M.J., K.W. Campbell, C.M. Maragos, C. Pilcher, J.M. Headrick, J.K. Pataky, and D.G. White.  2003.  Influence of Cry1Ab protein and hybrid genotype on fumonisin contamination and Fusarium ear rot in corn.   Crop Sci. 43:1283-1293.

Darrah, L.L. and M.S. Zuber. 1985.  United States farm maize germplasm base and commercial breeding strategies.  Crop Sci. 26:1109-1113.

Dudley, J.W.  1982.  Theory of transfer of alleles.  Crop Sci. 22:631-637.

Eberhart, S.A., W. Salhuana, R. Sevilla, and S. Taba.  1995. Principles for tropical maize breeding.  Maydica 40:339-355.

Edmeades, G.O., J. Bolanos,  S.C. Chapman, H.R. Laffite, and M. Banziger.  1999.  Selection improves drought tolerance in tropical maize populations: I.Gains in biomass, grain yield, and harvest index.  Crop Sci. 39:1306-1315.

Fehr, W.R.  1987.  Early-generation testing.  p. 339-346.  In Principles of Cultivar Development.  Vol.1.  MacMillan Pub. Co., New York.

Fergason, V.  2001.  High amylose and waxy corns. p. 63-84.  In  (A.R. Hallauer, Ed.),  Specialty Corns.  CRC Press LLC.

Gallais, A., and J.P. Monod.  2001.  A French cooperative program for management and utilization of maize genetic resources. p. 331-340.  In H.D. Cooper, C. Spillane, and T. Hodgkin (eds.).  Broadening the Germplasm Base of Crop Production.   CABI  Publishing, FAO and IPGRI.

Gethi, J.G., J.A. Labate, K.R. Lamkey, M.E. Smith, and S. Kresovich.  2002.  SSR variation in important U.S. maize inbred lines.  Crop Sci. 42:951-957.

Goodman, M.M. 1998.  Research policies thwart potential payoff of exotic germplasm.  Diversity 14:30-35.

Goodman, M.M. 1999.  Broadening the genetic diversity in maize by use of exotic germplasm. p. 139-148.  In J.G. Coors and S. Pandey (eds.).  International Symposium on the Genetics and Exploitation of Heterosis in Crops.  ASA,  Madison, WI.

Goodman, M.M. and W.L. Brown.  1988.  Races of Corn. P. 33-79.  In G.F. Sprague and J.W. Dudley (ed.)  Corn and Corn Improvement.  3rd ed.  Agon. Monogr. 18.  ASA, CSSA, and SSSA, Madison, WI.

Hallauer, A.R., W.A. Russell, and K.R. Lamkey. 1988.  Corn Breeding.  p. 463-564.  In G.F. Sprague and J.W. Dudley (ed.) Corn and Corn Improvement.  3rd ed.  Agon. Monogr. 18.  ASA, CSSA, and SSSA, Madison, WI.

Hallauer, A.R. 1978.  Potential of exotic germplasm for maize improvement. p. 229-247.  In D.B. Walden (ed.) Maize Breeding and Genetics.  John Wiley and Sons, New York.

Hibbard, B.E., L.L. Darrah, and  B.D. Barry.  1999.  Combining ability of a new resistance source for western corn rootworm (Coleoptera:Chrysomelidae) larvae in corn.  Maydica 44:133-139.

Ho, J.C., S.R. McCouch, and M.E. Smith.  2002.  Improvement of hybrid yield by advanced backcross QTL analysis in elite maize.   Theor. Appl. Genet. 105:440-448.

Hoffbeck, M.D., S.J. Openshaw, J.L. Geadelman, R.H. Peterson, and D.D. Stuthman.  1995.  Backcrossing and intermating in an exotic x adapted cross of maize.  Crop Sci. 35:1359-1364.

Holland, J.B., D.V. Uhr, D. Jeffers, and M.M. Goodman.  1998.  Inheritance of resistance to southern rust in tropical-by-corn-belt maize populations.  Theor. Appl. Genet. 96:232-241.

Holland, J.B., M.M. Goodman, and F. Castillo-Gonzalez.  1996.  Identification of agronomically superior Latin American accessions via multi-stage evaluations.  Crop Sci. 36:778-784.

Jellum, M.D. 1970.  Plant introductions of maize as a source of oil with unusual fatty acid composition.  J. Agric. Food Chem. 18:365-370.

Ji, Y.,  K. Seetharaman, K. Wong, L.M. Pollak, S. Duvick, J. Jane, and P.J. White.  2003.  Chapter 3.  Thermal and structural properties of unusual starches from developmental corn lines. In Carbohydrate Polymers (accepted).

Ji, Y.,  K. Seetharaman, L.M. Pollak, S. Duvick, J.-L. Jane, and P.J. White.  2002.  Effect of genotype and environment on the thermal properties of starches from developmental corn lines.  Corn Utilization Conference,  Kansas City, MO.

Kraja, A. and J.W.  Dudley.  2000.  Identification of tropical and temperate maize populations having favorable alleles for yield and other phenotypic traits.  Crop Sci. 40:941-947.

Kraja, A., J.W. Dudley, and D.G. White.  2000.  Identification of tropical and temperate maize populations having favorable alleles for disease resistance.  Crop Sci. 40:948-954.

Kresovich, S., A.J. Luango, and S.J. Schloss.  2002.  ‘Mining the gold’:  Finding allelic variants for improved crop conservation and use.  p. 379-386.  In J.M.M. Engels, V.R. Rao, and A.H.D. Brown (eds.).  Managing Plant Genetic Diversity.  CABI Publishing, Oxon, UK.

Lambert, R.J.  2001.  High-oil corn hybrids.  p. 131-154.  In (A.R. Hallauer, Ed.), Specialty Corns.  CRC Press LLC.

Lamkey, K.R., B.J. Schnicker, and A.E. Melchinger.  1995.  Epistasis in an elite maize hybrid and choice of generation for inbred line development.  Crop Sci. 35:1272-1281.

Li, R., M.S. Kang, O.J. Moreno, and L.M. Pollak.  2002.  Field resistance to Aspergillus flavus from exotic maize (Zea mays L.) germplasm.  Plant Genetic Resources Newsletter 130:11-15.

Melchinger, A.E., R.K. Gumber, R.B. Leipert, M. Vuylsteke, and M. Kuiper.  1998.  Prediction of testcross means and variances among F3 progenies of F1 crosses from testcross means and genetic distances of their parents in maize.  Theor. Appl. Genet.  96:503-512.

Naidoo, A.M., A.M. Forbes, C. Paul, D.G. White, and T.R. Rocheford.  2002.  Resistance to Aspergillus ear rot and aflatoxin accumulation in maize F1 hybrids.  Crop Sci. 42:360-364.

National Academy of Science.  1972.  Genetic vulnerability of major crops.  “Report of Committee on Genetic Vulnerability of Major Crops.”  Agric. Board., Div. Biol. Agric., NAS-NRC, Washington, D.C.

Pollak, L.M.  2003.  The history and success of the public-private project on Germplasm Enhancement of Maize (GEM).  Advances in Agronomy 78:45-87.

Pollak, L.M. and W. Salhuana.  2001.  The Germplasm Enhancement of Maize (GEM) Project: Private and public sector collaboration p. 319-329.  In H.D. Cooper, C. Spillane, and T. Hodgkin (eds.).  Broadening the Germplasm Base of Crop Production.  CABI Publishing, FAO and IPGRI.

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Singh, S.K., L.A. Johnson, P.J. White, J.-L. Jane, and L.M. Pollak.  2001.  Thermal properties and paste and gel behaviors of starches recovered from accessions used in the Germplasm Enhancement of Maize Project.  Cereal Chem. 78:315-321.

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Xu, W. and M. Blanco.  2003.  Mining genes from tropical maize germplasm to improve drought tolerance and corn earworm resistance.  CIMMYT  2003.  p.74-75. Book of Abstracts; Arnel R. Hallauer International Symposium on Plant Breeding, 17-22 August, 2003, Mexico City, Mexico, D.F.


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Significant Accomplishments – Michael H. Blanco


Ph.D. (Corn Breeding and Genetics), Univ. of Missouri – Columbia, MO, 1977.

M.S. (Plant Pathology), Pennsylvania State University – University Park, PA, 1973.

B.S. (Plant Pathology & Plant Genetics), Univ. of Georgia – Athens, GA, 1968.

Work Experience:

USDA-ARS, GS-14 Geneticist/GEM Project Coordinator, Ames, IA, 2002-present.

Director Plant Genetics and Breeding, Akkadix Corp, San Diego, CA 1995-2001.

Director-International Research, Mycogen Corp/Agrigenetics, San Diego, CA, 1989-1995.

Director of Research, McCurdy Seed Co, Fremont, IA, 1983-1989.

Research Station Manager, O’s Gold Seed Co., Farmer City, IL, 1977-1983.

Accomplishments over the past 10 years:

USDA-ARS, 2002-present:

GEM Project Coordinator, 2002-present.

Coordinated in kind support for nurseries, and yield trials with approximately 25 private companies and acted as ADODR for administration of SCA projects to support GEM’s objectives.

Managed on site breeding nursery in Ames, and supported activities for GEM in Raleigh, NC.

Akkadix Corp, 1995-2001:

Coordinated research collaboration for germplasm exchange, development, and yield testing for 25 companies throughout the world.  Registered the company’s first proprietary corn hybrid in Europe in 2001.  Worked with interdisciplinary teams including breeders, and plant scientists.

Mycogen Corp/Agrigenetics, 1989-1995:

Directed breeding activities and administrative operations of 3 international subsidiaries - Italy, France, Argentina,and a joint venture in India.  Registered 4 corn hybrids, and 7 sunflower hybrids in France along with Plant Breeder’s Rights documentation.  Developed 7 inbred corn lines that were used in 20 commercial hybrids in the US and Europe.

Research Interests:

Germplasm enhancement using temperate and tropical exotic germplasm that would have impact for broadening the germplasm base.

Identification of unique alleles for resistance to disease, insects, and mycotoxin production.

Applications of genomic technologies for phenotypic characterization and plant breeding.


Xu, W. and M. Blanco.  2003.  Mining genes from tropical maize germplasm to improve drought tolerance and corn earworm resistance.  CIMMYT 2003.  p.74-75. Book of Abstracts; Arnel R. Hallauer International Symposium on Plant Breeding, 17-22 August, 2003, Mexico City, Mexico, D.F.

17 publications authored or co-authored prior to 1993 included maize disease resistance studies.


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Health, Safety, and Other Issues of Concern Statement

Animal Care- Not applicable.

Endangered Species- Not applicable.

Environmental Impact Statement – The research project has been examined for potential impacts on the environment and has been found to be categorically excluded under ARS regulations for the National Environmental Policy Act.

Human Study Procedures – Not applicable.

Laboratory Hazards – Not applicable.

Occupational Safety & Health – The unit adheres to all USDA-ARS-MWA guidelines and also to those of Iowa State University.

Recombinant DNA Procedures – Not applicable.

While preparing the Project Plan, I, Michael Blanco, have carefully examined all aspects of the planned research to ensure that appropriate safety concerns are addressed, all necessary permits have been identified, and that environmental issues have been considered in making the National Environmental Policy Act (NEPA) decision documented in the statement.  All permits are hand or have been requested.  Documentation supporting NEPA decision is in the MU project file and available for review upon request.

I, Adrianna Hewings, Director, MWA certify that the proposed research conforms to current regulations and guidelines regarding the above issues and concerns.

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Appendix Table 2. Nursery & Testing Resources Required Relative to Numbers of Populations Worked








































Populations (W):




Selfing Rows in Each Year









S1 Nursery


S2 Nursery


Seed Increase


ISO Rows


Trial Plots

Populations (S):







































Populations (W):




Selfing Rows in Each Year









S1 Nursery


S2 Nursery


Seed Increase


ISO Rows


Trial Plots

Populations (S):

































































Populations (W):




Selfing Rows in Each Year









S1 Nursery


S2 Nursery


Seed Increase


ISO Rows


Trial Plots

Populations (S):







































Populations (W):




Selfing Rows in Each Year









S1 Nursery


S2 Nursery


Seed Increase


ISO Rows


Trial Plots

Populations (S):



























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We are grateful to our Cooperators for their support!

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