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ARS Home » Midwest Area » Ames, Iowa » Plant Introduction Research » Research » Research Project #424734

Research Project: Genetic Enhancement of the U.S. Maize Genepool with Unadapted Maize Germplasm

Location: Plant Introduction Research

Project Number: 5030-21000-059-000-D
Project Type: In-House Appropriated

Start Date: Feb 5, 2013
End Date: Feb 4, 2018

Objective 1: Manage and coordinate the Midwestern United States component of an ongoing, multi-site, cooperative program of maize germplasm evaluation, genetic enhancement, germplasm and inbred line development, and information sharing which seeks to broaden the genetic base for U.S. maize. Sub-objective 1A. Coordinate and manage in-kind support for evaluation, development, and genetic enhancement of GEM germplasm. Sub-objective 1B. Manage GEM field nurseries, germplasm exchange, and seed inventories to ensure that new sources of germplasm and information reach stakeholders annually. Sub-objective 1C. Implement website enhancements to identify GEM lines best suited for particular uses. Objective 2: Evaluate a wide diversity of unadapted temperate, sub-tropical and tropical maize germplasm for adaptation, yield, resistance to biotic stresses, tolerance to environmental extremes, and selected value-added, product quality traits. Sub-objective 2A. Evaluate 50-100 maize exotic breeding crosses and new sources of exotic germplasm annually for their adaptation to Midwestern U.S.; identify favorable agronomic traits; choose and prioritize germplasm for incorporation into breeding programs. Sub-objective 2B. With public and private-sector cooperators, evaluate maize germplasm for globally important leaf and stalk rot diseases, reduced ear mold and mycotoxin production, abiotic stress tolerance, host plant resistance to corn rootworm (CRW), multiple pest resistance for above ground insects, and key value-added traits such as highly digestible starch and resistant starch, bioenergy (ethanol) potential, and silage nutritional quality and productivity. Objective 3: Breed and release genetically-enhanced maize populations and inbred lines, derived from unadapted sub-tropical and tropical maize germplasm, that can contribute more diverse genetic resistance to biotic stresses, tolerance to environmental extremes, higher yield, unique product qualities, and other valuable new traits to new commercial hybrids. Sub-objective 3A. Develop and release a novel set of “adapted” maize races resulting from the allelic diversity (AD) project as tools for gene discovery and genomic research. Sub-objective 3B. Develop germplasm with key agronomic traits, such as enhanced silage value, reduced mycotoxin level, and biotic stress resistance. Disseminate germplasm information. Sub-objective 3C. Evaluate adaptation and topcross performance of a CUBA164 mapping population planted at multiple population densities. Objective 4: Apply and assess the efficacy of doubled-haploid and genomic technologies as tools for accelerating the incorporation of exotic genes into U. S.-adapted maize genepools. Sub-objective 4A. Develop doubled haploid (DH) maize lines from selected races in the AD project. Sub-objective 4B. Conduct phenotypic trait evaluation and genetically characterize DH lines.

Extensive collaboration efforts on the part of 52 current cooperators from the private, public and international sectors are required to broaden the germplasm base in effective ways that provide germplasm of use for food, feed, fuel, and industrial applications by producers and end-users. The Coordinator serves as the liaison for collaborators and the Technical Steering Group (TSG), selects germplasm, facilitates germplasm acquisition and stakeholder interactions, arranges for in-kind-support, information sharing, and technology transfer. The Ames location will develop germplasm derived from 50% and 25% exotic breeding crosses developed by crossing tropical and temperate racial accessions with adapted, elite proprietary Corn Belt lines. Breeding crosses will also be developed from GEM x GEM releases, and other models to maximize useful exotic germplasm contributions. Approximately 100 breeding crosses will be evaluated in three environments and ~30 selected annually for development in Ames or collaborator nurseries. Approximately 2,000 S2 top crosses will be made and evaluated annually in yield trials, disease nurseries, and for value-added traits such as ethanol, protein, oil, and starch. Germplasm will be further evaluated by a network of cooperators with expertise, facilities, and favorable selection environments for the traits of interest. Important traits include mycotoxin resistance, abiotic stress tolerance, and insect resistance. A concerted effort will be made to evaluate and develop germplasm for globally important diseases through our international network of cooperators. Germplasm lines will be released to cooperators and selected lines registered and publicly released. Released lines will be maintained by the National Plant Germplasm System. A tropical accession, CUBA164, will be studied for adaptability to high plant densities using a mapping population of ~400 BC1S2 plants that were top crossed to a common tester. Tissue will be sampled from the BC1S2 plants and genotyped by a collaborator. The genomic information from this study will be used to develop a genomic model to select lines for recycling. An effort will be made to develop lines derived from approximately 300 races of maize to broadly represent the allelic diversity of the maize races. Initial crosses of racial accessions with expired PVP lines or other public lines and one backcross to the adapted line (BC1) are made in winter nurseries. The resulting BC1 generation will be used for selecting lines in Midwest nurseries in order to release a unique set of (F5 generation) adapted, racial derivative lines for research and discovery. BC1 populations will also be used to develop doubled haploids (DH), and will be further studied by phenotypic evaluation and genotypic characterization using current technologies such as genotype by sequencing (GBS). Genotypes will be screened in selected environments to maximize selection for priority agronomic, biotic and abiotic stress, reduced mycotoxin, and value-added traits.