Location: Plant Introduction Research2010 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
Progress was made on all four objectives and sub-objectives. On July 18, a severe wind storm in excess of 70 mph caused significant damage to various sections of the GEM nursery. The extent of damage ranged from as high as ~30% in some sections to about 5% in other sections of the nursery. Overall, approximately 15% of the 6,400 nursery rows were wind- snapped or severely root lodged making pollinations impossible or very difficult to reach the intended number required. As a result, an increase in winter nursery use will be necessary. An important objective is the development of adapted exotic inbred lines representing 300 races of maize using double haploid and traditional plant breeding methods. Through the combined support of two private GEM cooperators, 423 rows of doubled haploid (DH) families developed in Ames, IA, were planted in winter nurseries in Hawaii and Chile to increase seed for the 2010 GEM nursery. Approximately 300 DH families were returned from the two winter nurseries and planted for seed increase. In addition, 78 new haploid populations representing 42 races (4,030 plants) were treated at the three leaf stage with a chromosome doubling agent, colchicine, grown in the greenhouse for two weeks, and transplanted in the nursery. Since haploid tassels are very sensitive to intense sunlight, an overhead temporary shade structure (18 feet x 360 feet) was constructed above the haploid plants to reduce sun light intensity by 30%. (The shade structure was destroyed by the windstorm of July 18). Approximately 319 plants were identified as potential doubled haploids and self pollinated before the wind storm. For the traditional breeding program, approximately 419 nursery rows were devoted to the Allelic Diversity (AD) project which comprised 85 races from 10 countries. Presently, 176 races from 189 accessions are at the first back cross (BC1) stage (or later generation of inbreeding). Approximately 17,700 yield trial plots were planted at 49 trial locations with the combined effort of the GEM Project and 14 private cooperators. Efforts are continuing to create an exotic mapping population using CUBA164 (PI 489361) as the elite exotic source identified in the GEM Project. The second selfing (S2) generation was made from the backcross (BC) families to create the BC1S2 generation of 241 families of (CUBA164 x B73) x B73, and 241 families (CUBA164 x PHB47) x PHB47. Two new cooperators joined the Germplasm Enhancement of Maize (GEM) Project. Semilia Genetica, a private cooperator from Brazil, and the Louisiana State University Agricultural Center. The new cooperators will expand our access to exotic tropical germplasm, and enhance our ability to evaluate germplasm for aflatoxin resistance. Other research collaborations in progress with the public and private sectors include germplasm evaluation and/or development with nine Universities, two private companies, and five USDA-ARS research units for mycotoxin, abiotic stress, southern leaf blight, grey leafspot, corn root worm, multiple insect resistance, amino acid evaluation, and starch properties for ethanol potential and resistant starch.
1. Doubled Haploid's (DH) of allelic diversity germplasm. An important objective of the allelic diversity project is to capture the genetic variation represented in over 300 exotic corn races. This requires an extensive adaptation process by crossing exotic maize races to Corn Belt germplasm followed by selection and inbreeding. Collaborating with Iowa State University scientists, GEM ARS researchers at the Plant Introduction Unit in Ames, IA, implemented a DH method to attain homozygous uniform plants in two growing seasons versus the 8-10 seasons normally required for traditional inbreeding. Beginning in 2008, breeding populations from the GEM allelic diversity project were crossed to an inducer to make haploids (plants with half the chromosome number), and were doubled the following year to attain diploid homozygous (uniform) plants. Approximately 300 inbred lines representing 44 races were identified and planted for increase in 2010. This accomplishment can accelerate development of adapted inbreds derived from ~300 exotic races and potentially provide valuable genetic resources to the maize community.
Srichuwong, S., Gutsea, J., Blanco, M.H., Duvick, S.A., Gardner, C.A., Jane, J. 2010. Characterization of Corn Grains for Ethanol Production. Journal of ASTM International. 7(2):1-10.