Location: Plant Introduction Research2012 Annual Report
1a. Objectives (from AD-416):
The long-term objectives of this project are to identify and incorporate useful maize genetic diversity to support sustainable productivity of the most important crop in the United States, as measured by acreage planted, farm gate value, product value and strategic importance. To accomplish this, we will: 1) manage and coordinate a multi-site, cooperative program of maize germplasm evaluation, genetic enhancement, inbred line development, and information sharing focused on broadening the genetic base for U. S. maize; 2) evaluate maize germplasm with a broad spectrum of non-U.S. and mixed U.S./non-U.S. pedigrees for adaptation, yield, resistance to biotic and abiotic stresses, and key value-added traits; 3) breed and release genetically-enhanced populations and inbred lines, derived from non-U.S. and/or mixed U.S./non-U.S. germplasm sources, that are commercially-competitive and/or which contain key traditional or novel traits; and 4) develop innovative means of managing and transferring evaluation and breeding information to multiple project cooperators and germplasm users.
1b. Approach (from AD-416):
Extensive collaboration efforts on the part of 60 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. Approximately 1,500 -1,600 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. 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's maize curator. An effort will be made to develop lines derived from approximately 250 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 are made in winter nurseries, and one backcross to the adapted line (BC1). 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 applications. Technologies and methodologies can be utilized such as SNP or SSR markers for genomic profiling and association analysis that offer potential to translate genomic knowledge to germplasm enhancement and utilization applications. Genotypes will be screened in selected environments to maximize selection for priority agronomic, biotic and abiotic stress, reduced mycotoxin, and value-added traits.
3. Progress Report:
Severe drought and heat in all Midwest states will impact trial results and the productivity of the Ames nursery; extent of losses will not be known until harvest. Six new GEM releases were distributed to cooperators for the 2012 season. One release, GEMS-0226, had protein content of 13.4% (vs 9-10% for most Corn Belt hybrids). Presently, 244 lines have been released by the GEM Project, of which 170 are publicly available via the Genetic Resources Information Network (GRIN). Approximately 13,100 yield trial plots were planted at 46 trial locations with the combined efforts of the GEM Project and 12 private cooperators. The evaluation of breeding crosses is an important objective to determine adaptability and prioritization of exotic material for development. One hundred breeding crosses were planted at three locations in 2012 in collaboration with two cooperators, AgReliant, and G and S Crop Services. The objective of the Allelic Diversity (AD) project is to develop adapted exotic inbred lines representing ~300 races of maize. To achieve this objective, traditional selfing and doubled haploid methods are used. Approximately 594 nursery rows were devoted to traditional selfing of AD germplasm, comprised of 115 races from 14 countries in 2012. More than 300 accessions from 200 races are in use in the AD project's developmental pipeline. The haploid inducer line currently used is very early, has low seed yield, and is not adapted to the Midwest. Breeding efforts to develop a new inducer consisted of 90 rows of S3 families that were self pollinated and crossed to a tester line to evaluate their potential as new haploid inducer lines. A testcross isolation block of 452 BC1S2 families of a CUBA164 mapping population was planted in collaboration with Pioneer Hi-Bred, a DuPont business. This includes an equal number of BC1S2 families from CUBA164 x B73) x B73, and BC1S2 families from CUBA164 x PHB47) x PHB47 (~226 families each). Future objectives of this project include identification and mapping of genes involved in adaptation to high plant density, and distribution to the maize community for other studies. Aflatoxin content: two lines were identified with reduced content in collaboration with the USDA-ARS Corn Host Plant Resistance Research Unit (CHPRRU) in Starkville, MS. Inbred KO679Y (PI 591017), and GEM inbred CUBA117:S15-101-1-B-B-B-B were reported to contribute to reduced content in crosses with two inbreds developed by CHPRRU, Mp717 and Mp794, and with other two GEM lines, GEMN-0130 and GEMN-0140. (Henry et al. 2012). Additional crosses with KO679Y and CUBA117:S15-101-1-B-B-B-B were made in the 2012 nursery for future use.
1. New sources of Doubled Haploid (DH) inbreds. The corn germplasm base in the U.S. is extremely narrow and lack of genetic diversity can lead to genetic vulnerability to pathogens and insects, and limit genetic gain from selection. The Germplasm Enhancement of Maize (GEM) Project utilizes doubled haploid (DH) technology to expedite development of inbreds from populations derived from exotic races. In the past year, 38 additional DH inbreds from 11 races were developed; 417 total DH inbreds now represent 85 maize races. The DH lines are being increased in 2012 for future research and distribution to the maize community. Utilization of DH technology accelerates the inbreeding process by reducing cycle time from the traditional 8 generations to 3 generations, and will provide valuable genetic resources to broaden the germplasm base with potentially unique alleles.
Brenner, E., Blanco, M.H., Gardner, C.A., Lubberstedt, T. 2012. Genotypic and phenotypic characterization of isogenic doubled haploid exotic introgression lines in maize. Molecular Breeding. 30:1001-1016. Available: http://www.springerlink.com/content/g6l3662104697881/?MUD=MP.