Progress 11/02/03 to 01/08/08
Outputs
Progress Report Objectives (from AD-416) This project has three main objectives, all related to broadening the genetic base of the U.S. corn crop by identifying favorable genes in exotic genetic resources and creating genomics-assisted breeding techniques to incorporate them into the U.S. maize gene pool. Objective 1: Identify chromosomal regions at which exotic maize lines possess genes with agronomic effects superior to those carried in Corn Belt lines. At the same time, the exotic gene regions that cause photoperiod sensitivity, the major problem of adaptation of tropical corn to U.S. growing environments, will be mapped. This will permit rapid elimination of these unfavorable genes when introducing tropical maize germplasm into Corn Belt populations. Objective 2: Identify sources of resistance to Fusarium ear rot disease and accumulation of the mycotoxin fumonisin, map the genes conferring resistance, and combine multiple resistance genes into a single breeding line. Genetic research on Fusarium ear rot and the causes of fumonisin accumulation is to be strenghtened to focus on identifying genes that prevent or reduce accumulation of fumonosin. Additionally, research on gray leaf spot and other emerging diseases of corn is to be expanded to assist plant-breeding efforts to prevent losses from these diseases. Objective 3: Characterize the frequency and importance of gene interactions (epistasis) on agronomically important traits of varying complexity. If a gene's effect depends on the presence of specific forms of other genes in the genetic background, then epistasis is important, and DNA marker-assisted selection and exotic germplasm breeding schemes will require modification to exploit this genetic phenomenon. Approach (from AD-416) Gene mapping techniques based on DNA markers and linkage analysis will be used to identify chromosomal regions affecting the traits studied. DNA marker-assisted selection will be used to transfer favorable genes from exotic sources into adapted genetic backgrounds, verify their effects, and provide unique germplasm lines that can be incorporated easily into commercial hybrid breeding programs. Phenotypic expression of target traits will be assayed by using large-scale field evaluations (for yield and related traits), greenhouse and field environments with divergent daylengths (for photoperiod sensitivity), and by inoculating mapping lines with fungi that cause Fusarium ear rot and fumonisin contamination (for disease resistance). Fumonisin contamination will be assayed using antibody-based laboratory analyses. Significant Activities that Support Special Target Populations New genetic mapping lines that will allow higher resolution mapping of genes for response to photoperiod were constructed. Analysis of 14 complex traits measured on 26 new genetic mapping populations was completed, permitting very high-resolution analysis of this diverse population for genes controlling these traits. More than 20 genome regions containing southern leaf blight resistances were identified in this population. The best 80 backcross-derived families were tested in two locations for resistance to Fusarium ear rot and in four locations for hybrid yield potential. The best 20 lines from a new genetically diverse population segregating for resistance to Fusarium ear rot were intermated to form a new cycle population for continued selection in the future. 50 advanced lines from the USDA Germplasm Enhancement of Maize project and the North Carolina State University maize inbred development programs were tested for resistance to Fusarium ear rot and fumonisin resistance. We have begun the analysis of several near isogenic lines in controlled growth chamber conditions and have shown that resistance observed in the field is also usually observed under control environment conditions (with much younger plants). We have begun fine-mapping two quantitative trait gene regions for southern leaf blight using F2:3 populations. This progress addresses Component 3 Genetic Improvement of Crops, Problem Statement 3C Germplasm Enhancement/Release of Improved Genetic Resources and Varieties of the National Program 301 Plant Genetic Resources, Genomics, and Genetics Improvement. Replacement project 6645-21220-013-00D.
Impacts
(N/A)
Publications
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) This project has three main objectives, all related to broadening the genetic base of the U.S. corn crop by identifying favorable genes in exotic genetic resources and creating genomics-assisted breeding techniques to incorporate them into the U.S. maize gene pool. Objective 1: Identify chromosomal regions at which exotic maize lines possess genes with agronomic effects superior to those carried in Corn Belt lines. At the same time, the exotic gene regions that cause photoperiod sensitivity, the major problem of adaptation of tropical corn to U.S. growing environments, will be mapped. This will permit rapid elimination of these unfavorable genes when introducing tropical maize germplasm into Corn Belt populations. Objective 2: Identify sources of resistance to Fusarium ear rot disease and accumulation of the mycotoxin fumonisin, map the genes conferring resistance, and combine multiple resistance genes into a single breeding line. Genetic research on Fusarium ear rot and the causes of fumonisin accumulation is to be strenghtened to focus on identifying genes that prevent or reduce accumulation of fumonosin. Additionally, research on gray leaf spot and other emerging diseases of corn is to be expanded to assist plant-breeding efforts to prevent losses from these diseases. Objective 3: Characterize the frequency and importance of gene interactions (epistasis) on agronomically important traits of varying complexity. If a gene's effect depends on the presence of specific forms of other genes in the genetic background, then epistasis is important, and DNA marker-assisted selection and exotic germplasm breeding schemes will require modification to exploit this genetic phenomenon. Approach (from AD-416) Gene mapping techniques based on DNA markers and linkage analysis will be used to identify chromosomal regions affecting the traits studied. DNA marker-assisted selection will be used to transfer favorable genes from exotic sources into adapted genetic backgrounds, verify their effects, and provide unique germplasm lines that can be incorporated easily into commercial hybrid breeding programs. Phenotypic expression of target traits will be assayed by using large-scale field evaluations (for yield and related traits), greenhouse and field environments with divergent daylengths (for photoperiod sensitivity), and by inoculating mapping lines with fungi that cause Fusarium ear rot and fumonisin contamination (for disease resistance). Fumonisin contamination will be assayed using antibody-based laboratory analyses. Significant Activities that Support Special Target Populations Molecular marker maps of four new mapping populations segregating for response to photoperiod were constructed. Gene regions controlling flowering time response to photoperiod were identified with these maps. 25 new additional genetic mapping populations were made and tested in summer and winter nurseries for more than 20 complex traits related to adaptation and productivity. More than 400 backcross-derived families were tested in two locations for resistance to Fusarium ear rot, and the best 20 families were selected and sent to winter nursery to generate 80 new sub-lines for further testing. A genetically diverse population segregating for resistance to Fusarium ear rot and agronomic potential was created and self-fertilized one generation to produce 200 new experimental lines. These lines were planted in two locations in the summer season to evaluate their ear rot resistance and yield potential. 50 advanced lines from the USDA Germplasm Enhancement of Maize project and the North Carolina State University maize inbred development programs were tested for resistance to Fusarium ear rot and fumonisin resistance. Genes for quantitative (partial) disease resistance previously identified in this project were transferred by traditional breeding methods into a common background to verify their effects. Several provided significantly enhanced levels of resistance. Several genome regions containing genes for resistance to southern leaf blight (SLB), grey leaf spot (GLS) and northern leaf blight (NLB) were mapped in different segregating populations, including several using a high-resolution mapping population. Evidence for gene regions conferring multiple disease resistance was developed in two ways. First, several gene regions were identified that provided resistance to more than one disease; Second a strong genetic correlation was identified between resistances to GLS, SLB and NLB in a diverse 300-line population. Accomplishments High-resolution mapping of a quantitative disease resistance gene. Quantitative disease resistance genes contribute to durable control of diseases in commercial corn, but little is known about the identity or function of these genes. We demonstrated that the position of such genes in the genome can be identified with much greater precision using specialized populations resulting from several generations of random- mating compared to typical mapping populations. This discovery will lead to more rapid identification of the actual genes involved in quantitative disease resistance and improved capability to improve durable disease resistance in maize. This addresses Component 2 (Crop Informatics, Genomics, and Genetic Analyses), Problem Statement 2C (Genetic Analyses and Mapping of Important Traits) of the National Program 301 action plan. Technology Transfer Number of Web Sites managed: 2 Number of Non-Peer Reviewed Presentations and Proceedings: 3 Number of Newspaper Articles,Presentations for NonScience Audiences: 4
Impacts
(N/A)
Publications
- Krakowsky, M.D., Lee, M., Holland, J.B. 2007. Genotypic correlation and multivariate qtl analyses for cell wall components and resistance to stalk tunneling by the european corn borer in maize. Crop Science 47:485-488.
- Holland, J.B. 2007. Genetic Architecture of Complex Traits in Plants. Current Opinion in Plant Biology. 10:156-161.
- Holland, J.B., Robertson-Hoyt, L., Betran, J., Payne, G., White, D., Isakeit, T., Maragos, C.M., Molnar, T. 2007. Relationships among resistances to Fusarium and Aspergillus ear rots and contamination by fumonisin and aflatoxin in maize. Phytopathology. 97(3):311-317.
- Balint Kurti, P.J., Krakowsky, M.D., Robertson, L., Jines, M., Molnar, T., Goodman, M., Holland, J.B. 2006. Identification of quantitative trait loci for resistance to southern leaf blight and days to anthesis in a maize recombinant inbred line population. Phytopathology. 96:1067-1071.
- Robertson, L., Jines, M., Balint Kurti, P.J., Kleinschmidt, C., White, D., Payne, G., Maragos, C.M., Holland, J.B. 2006. Qtl mapping for fusarium ear rot and fumonisin contamination resistance in two populations of maize (zea mays). Crop Science 46:1734-1743.
- Jines, M.P., Balint Kurti, P.J., Robertson-Hoyt, L.A., Molnar, T., Holland, J.B., Goodman, M.M. 2006. Mapping resistance to southern corn rust in a semi-tropical recombinant inbred topcross population.. Theoretical and Applied Genetics. 114:659-667.
- Gonzalo, M., Vyn, T.J., Holland, J.B., Mcintyre, L.M. 2007. Mapping reciprocal effects and interactions with plant density stress in zea mays l.. Heredity. 99:14-30.
- Szalma, S.J., Hostert, B., Ledeaux, J., Stuber, C.W., Holland, J.B. 2007. Qtl mapping with near-isogenic lines in maize. Theoretical and Applied Genetics. 114:1211-1228.
- Carson, M.L., Balint Kurti, P.J., Blanco, M.H., Duvick, S.A., Millard, M., Hudyncia, J., Goodman, M. 2006. Registration of 9 high-yielding maize germplasms adapted for the southern US, derived from tropical by temperate crosse. Crop Science. 46:1825-1826.
- Gao, X., Shim, W., Gobel, C., Kunze, S., Feussner, I., Meeley, R., Balint Kurti, P.J., Kolomiets, M. 2007. Disruption of a maize 9-lipoxygenase results in increased resistance to fungal pathogens and reduced levels of contamination with mycotoxin fumonisin. Molecular Plant-Microbe Interactions. 20:922-933.
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Progress 10/01/05 to 09/30/06
Outputs
Progress Report 1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter? This research is relevant to National Program 301, Plant Genetic Resources, Genomics, and Genetic Improvement. The genetic base of U.S. field corn is narrow relative to the total genetic diversity available in the species worldwide. The limited genetic base of U.S. corn may leave the crop susceptible to newly evolved strains of pathogens and it may limit breeding gains for important agronomic traits. This project has two main objectives, all related to enhancing understanding of the genetic diversity in maize and the inheritance of complex traits, with the practical goal of broadening the genetic base of the U.S. corn crop by identifying favorable genes in exotic genetic resources and creating genomics-assisted breeding techniques to incorporate them into the U.S. maize gene pool. The
first major objective is to develop the genetic resources and methodologies to identify both favorable and unfavorable genes in exotic maize affecting agronomically important traits. Specific projects with this objective include mapping genes in exotic maize lines possess that cause photoperiod sensitivity (the primary cause of poor adaptation of tropical corn to the U.S. Corn Belt) or improved agronomic performance. The second major objective is to identify and analyze genes for resistance to major corn diseases, including Southern Corn Leaf Blight, Gray Leaf Spot, and Fusarium ear rot. Multiple genes control resistance to these diseases, so we are examining diverse sources of resistance for useful genes and developing resources for the in depth analysis of some of these genes. Potential impact of the work is the creation of improved corn lines that can improve the productivity and disease resistance of hybrids grown by farmers. In addition, a diversity- based collection of maize
populations will be made publicly available to be used for mapping the specific genetic components responsible for phenotypic variation of quantitative traits, which could be directly incorporated into worldwide breeding efforts. 2. List by year the currently approved milestones (indicators of research progress) The milestones for this project are a combination derived from the merger of this CRIS with a former CRIS project researching quantitative disease resistance in maize. FY2004- Initiate greenhouse evaluations of photoperiod-sensitive and insensitive lines and backcross (introgress) exotic lines to a standard temperate line; Begin phenotypic evaluations for Fusarium/fumonisin resistance; Begin development of genetic stocks with pairs of introgressed chromosome segments to test epistasis. FY2005-Complete greenhouse evaluations of photoperiod-sensitive and insensitive lines and backcross (introgress) exotic lines to a standard temperate line for two generations; Complete 2nd year
of phenotypic evaluations for Fusarium/fumonisin resistance; Complete development of genetic stocks with pairs of introgressed chromosome segments to test epistasis; Develop a controlled environment assay for southern leaf blight and use it to map quantitative trait loci (QTLs); Develop a cercosporin bioassay; and Develop a controlled environment assay for gray leaf spot. FY2006-Complete photoperiod mapping population development and parental screenings and to create backcross-inbred introgression lines; Complete genetic mapping of Fusarium resistance genes; Complete genotyping and phenotyping of stocks used for epistasis mapping; Complete construction of southern leaf blight and gray leaf spot QTL near-isogenic lines; Determine resistance phenotypes of selected mutants; and complete QTL mapping in RIL populations. FY2007-Complete field and greenhouse phenotyping of photoperiod mapping populations and complete first year of phenotyping of introgression lines; Identify new sources of
resistance to Fusarium ear rot and initiate new mapping populations; Identify chromosomal regions interacting at molecular and phenotypic levels; Complete phenotypic analysis of disease resistance near-isogenic lines FY2008-Complete mapping of photoperiod response genes and favorable genes from exotic maize stocks; Complete introgression of Fusarium resistance genes into an adapted genetic stock; Release superior genetic stocks with two introgressions; and finish screening of 302 lines and determine relationships between maturity and disease resistance 4a List the single most significant research accomplishment during FY 2006. This accomplishment is aligned with ARS National Program 301 Plant Genetic Resources, Genomics, and Genetic Improvement Component 3, Genetic Improvement of Crops. Resistance to southern leaf blight and to gray leaf spot diseases are genetically correlated across a diverse sample of maize lines. This accomplishment addresses problem statement 3B, Capitalizing on
Untapped Genetic Diversity. The maize crop of the USA has limited genetic diversity and is vulnerable to both southern leaf blight and gray leaf spot diseases. We discovered that the genetic basis of partial resistances to these two diseases are correlated in a set of more than 250 inbred lines sampled from breeding programs around the world. This result suggests that there may be common molecular mechanisms of resistance to these two diseases (caused by unrelated fungi) , and perhaps to other leaf blights as well. New sources of resistance were discovered in this set of lines. The outcome of this result will be to simplify the search for underlying disease resistance genes and their deployment in maize cultivars. 5. Describe the major accomplishments to date and their predicted or actual impact. NP301, component 3, problem statement 3B. Major accomplishments over the life of the project include the identification of semi-tropical maize inbred lines developed from crosses between
tropical maize accessions and a temperate-adapted inbred line that produce better hybrids than their temperate parent. Using DNA markers, we demonstrated these lines contain large amounts (at least 30%) of genes from Latin American maize collections, which are not otherwise represented in the USA maize breeding pool. A set of 29 semi-exotic lines with excellent hybrid production capacity that was developed as part of the Germplasm Enhancement of Maize project was publicly released. Another set of lines was tested to evaluate the effectiveness of a new marker-assisted breeding method, the near-isogenic line method. Yield trial results demonstrate that the method is effective at identifying favorable alleles from donor parents in standard inbred line backgrounds. It was also used to identify gene regions affecting resistance to stress associated with high planting density in corn. The relationship between genes affecting Fusarium ear rot and fumonisin contamination was clarified,
leading to a scientific basis for more efficient breeding programs to improve resistance to these aspects of corn ear rot. Similarly, the relationship between resistance to gray leaf spot and southern leaf blight diseases was uncovered. Our customers are primarily public and private maize breeders and geneticists. The methods developed have been adopted in other breeding programs, and the released germplasm has been used by other researchers and breeders for genetic mapping studies and applied maize breeding programs. We expect that this will lead to a broader genetic base and enhanced disease resistance for the U. S. corn crop, helping to ensure sustainable production. 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The near-isogenic line method of
introgressing specific chromosomal segments into a standard genetic background can be adopted by commercial corn breeding programs immediately. Semi-tropical inbred lines are being used by public maize breeding programs in Wisconsin and a new set of semi- exotic lines with improved performance has just been released to the public. The major constraints to the adoption of tropical maize-derived germplasm lines by commercial corn breeding programs is that even the lines that have good yield potential tend to have other agronomic deficiencies, such as poor seed production as inbred lines, poor lodging resistance, and unfavorable grain moisture characteristics. Nevertheless, such lines will be useful to commercial breeders as parents of new breeding populations.
Impacts
(N/A)
Publications
- Balint Kurti, P.J., Blanco, M.H., Duvick, S.A., Holland, J.B., Clements, M. J., Holley, R., Carson, M.L., Goodman, M.M. 2006. Release of 20 GEM breeding families adapted for the southern US. Crop Science. 46:996-998.
- Balint Kurti, P.J., Carson, M.L. 2006. Analysis of quantitative trait loci for resistance to southern leaf blight in juvenile maize.. Phytopathology.
- Lecain, D.R., Morgan, J.A., Milchunas, D.G., Mosier, A.R., Nelson, J.A., Smith, D.P. 2006. Root biomass of individual species, and root size characteristics after five years of CO2 enrichment on native shortgrass steppe. Plant and Soil Journal. 279:219-228.
- Gonzalo, M., Vyn, T., Holland, J.B., Mcintyre, L. 2006. Mapping density response in maize: a direct approach for testing genotype and treatment interaction. Genetics.
- Holland, J.B. 2006. Estimating genotypic correlations and their standard errors using multivariate restricted maximum likelihood estimation with sas proc mixed. Crop Science.
- Holland, J.B. 2006. Theoretical and biological foundations of plant breeding.. Symposium Proceedings.
- Holland, J.B., Bretting, P.K., Bubeck, D.M., Cardinal, A.J., Holley, R.N., Uhr, D.V. 2006. Major m. goodman: a laudation. Maydica.
- Long, J., Holland, J.B., Munkvold, G., Jannink, J. 2006. Responses to selection for partial resistance to crown rust in oat. Crop Science.
- Robertson, L.A., Kleinschmidt, C.E., White, D.G., Payne, G.A., Maragos, C. M., Holland, J.B. 2006. Heritabilities and correlations of Fusarium ear rot resistance and fumonisin contamination resistance in two maize populations. Crop Science. 46:353-361.
- Robertson, L.A., Payne, G.A., Holland, J.B. 2006. Marker assisted breeding for host resistance to mycotoxin contamination. Book Chapter.
- Starr, M.R., Robertson-Hoyt, L.A., Payne, G.A., Holland, J.B. 2006. Improviing resistance to fumonisin contamination in maize. Illinois Corn Breeders School Proceedings.
- Tarter, J.A., Holland, J.B. 2006. Gains from selection during the development of superior semiexotic inbred lines from latin american maize accessions. Maydica.
- Balint Kurti, P.J., Nelson, R., Wisser, R. 2006. The genetic architecture of disease resistance in maize: a systhesis of published studies. Phytopathology.
- Yu, J., Pressoir, G., Briggs, W., Vroh, B., Yamasaki, M., Doebley, J.F., Mcmullen, M.D., Gaut, B.S., Holland, J.B., Kresovich, S., Buckler Iv, E.S. 2006. A unified mixed-model method for association mapping accounting for multiple levels of relatedness. Nature Genetics. 38:203-208.
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Progress 10/01/04 to 09/30/05
Outputs
1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter? The genetic base of U.S. field corn is narrow relative to the total genetic diversity available in the species worldwide. The limited genetic base of U.S. corn may leave the crop susceptible to newly evolved strains of pathogens and it may limit breeding gains for important agronomic traits. This project has three main objectives, all related to enhancing understanding of the genetic diversity in maize and the inheritance of complex traits, with the practical goal of broadening the genetic base of the U.S. corn crop by identifying favorable genes in exotic genetic resources and creating genomics-assisted breeding techniques to incorporate them into the U.S. maize gene pool. This research is relevant to National Program 301, Plant Genetic Resources. The first major objective is to develop the
genetic resources and methodologies to identify both favorable and unfavorable genes in exotic maize affecting agronomically important traits. Specific projects with this objective include mapping genes in exotic maize lines possess that cause photoperiod sensitivity (the primary cause of poor adaptation of tropical corn to the U.S. Corn Belt) or improved agronomic performance. The second major objective is to leverage modern genomics technologies to create new methods to identify genes and gene networks affecting quantitative traits of maize in a high throughput manner. Projects include the development of hybrids to investigate the genetic and epigenetic components of hybrid vigor in maize; the creation of mapping populations founded in the natural diversity present in maize to facilitate high resolution identification of genetic components of important traits; the identification of regions of the genome, specific genes, and the hierarchy of alleles responsible for phenotypic
variation through a marriage of classical linkage mapping and association analysis approaches; and the characterization of the frequency and importance of gene interactions on agronomically important traits of varying complexity. The third objective is to identify and analyze genes for resistance to major corn diseases, including Southern Corn Leaf Blight, Gray Leaf Spot, and Fusarium ear rot. Multiple genes control resistance to these diseases, so we are examining diverse sources of resistance for useful genes and developing resources for the in depth analysis of some of these genes. Potential impact of the work is the creation of improved corn lines that can improve the productivity and disease resistance of hybrids grown by farmers. In addition, a diversity-based collection of maize populations will be made publicly available to be used for mapping the specific genetic components responsible for phenotypic variation of quantitative traits, which could be directly incorporated
into worldwide breeding efforts. 2. List the milestones (indicators of progress) from your Project Plan. The milestones for this project are a combination derived from the merger of this CRIS with two former CRIS projects researching quantitative disease resistance in maize, and molecular genetics of maize. Year 1 (FY2004) 1. Initiate greenhouse evaluations of photoperiod-sensitive and insensitive lines and backcross (introgress) exotic lines to a standard temperate line. 2. Begin phenotypic evaluations for Fusarium/fumonisin resistance. 3. Begin development of genetic stocks with pairs of introgressed chromosome segments to test epistasis. 4. Develop a half-diallel set of crosses between diverse maize inbred lines. 5. Begin multiple-location yield trials to evaluate the 351 hybrids of the 27 X 26 half-diallel population for traits of agronomic interest and characteristics of hybrid vigor; Year 2 (FY2005) 1. Complete greenhouse evaluations of photoperiod-sensitive and
insensitive lines and backcross (introgress) exotic lines to a standard temperate line for two generations. 2. Complete 2nd year of phenotypic evaluations for Fusarium/fumonisin resistance. 3. Complete development of genetic stocks with pairs of introgressed chromosome segments to test epistasis. 4. Complete a 27 X 26 half-diallel set of crosses between diverse maize inbred lines. 5. Complete selfing of the 351 hybrids to create F2 seed. 6. Complete selfing and intermating within F2 populations to generate F2:3 and intermated F2 seed for continued population development. 7. Complete multiple-location yield trials to evaluate the 351 hybrids of the 27 X 26 half-diallel population for traits of agronomic interest and characteristics of hybrid vigor. 8. Develop a controlled environment assay for southern leaf blight and use it to map quantitative trait loci (QTLs) in the Mo17 x B73 mapping population. 9. Scale-up a cercosporin bioassay. 10. Develop a controlled environment assay
for gray leaf spot. Year 3 (FY2006) 1. Complete photoperiod mapping population development and parental screenings and to create backcross-inbred introgression lines. 2. Complete genetic mapping of Fusarium resistance genes. 3. Complete genotyping and phenotyping of stocks used for epistasis mapping. 4. Complete genotypic and phenotypic evaluation of maize F2:3 populations to determine significant genetic components for agronomically important traits including resistance to corn earworm and relevant maize pathogens. 5. Complete generation of F3:4 and F4:5 seed from the 351 maize F2:3 populations of the 27 X 26 half-diallel, and begin to increase the size of populations relevant to the investigation of corn earworm resistance, ethanol production efficiency, and resistance to maize diseases. 6. Complete multiple-location yield trials of relevant entries from FY 2005 yield trials. 7. Complete construction of southern leaf blight and gray leaf spot QTL near-isogenic lines. 8.
Complete QTL mapping in B104 x NC300, A619 x H99, and Ki14 x B73 RIL populations. Year 4 (FY2007) 1. Complete field and greenhouse phenotyping of photoperiod mapping populations and complete first year of phenotyping of introgression lines. 2. Identify new sources of resistance to Fusarium ear rot and initiate new mapping populations. 3. Identify chromosomal regions interacting at molecular and phenotypic levels. 4. Complete production of F5:6 seed from 351 maize populations and F6:7 seed from 175 maize populations. 5. Complete phenotypic analysis of disease resistance near-isogenic lines. Year 5 (FY2008) 1. Complete mapping of photoperiod response genes and favorable genes from exotic maize stocks. 2. Complete introgression of Fusarium resistance genes into an adapted genetic stock. 3. Complete the evaluation of epigenetic components contributing to hybrid vigor in maize. 4. Finish screening of 302 lines and determine relationships between maturity and disease resistance. 3a
List the milestones that were scheduled to be addressed in FY 2005. For each milestone, indicate the status: fully met, substantially met, or not met. If not met, why. 1. Complete greenhouse evaluations of photoperiod-sensitive and insensitive lines and backcross (introgress) exotic lines to a standard temperate line for two generations. Milestone Fully Met 2. Complete 2nd year of phenotypic evaluations for Fusarium/fumonisin resistance. Milestone Fully Met 3. Complete development of genetic stocks with pairs of introgressed chromosome segments to test epistasis. Milestone Fully Met 4. Complete a 27 X 26 half-diallel set of crosses between diverse maize inbred lines. Milestone Fully Met 5. Complete selfing of the 351 hybrids to create F2 seed. Milestone Fully Met 6. Complete selfing and intermating within F2 populations to generate F2:3 and intermated F2 seed for continued population development. Milestone Fully Met 7. Complete multiple-location yield trials to evaluate the 351
hybrids of the 27 X 26 half-diallel population for traits of agronomic interest and characteristics of hybrid vigor. Milestone Fully Met 8. Develop a controlled environment assay for southern leaf blight and use it to map quantitative trait loci (QTLs) in the Mo17 x B73 mapping population. Milestone Fully Met 9. Scale-up a cercosporin bioassay. Milestone Substantially Met 10. Develop a controlled environment assay for gray leaf spot. Milestone Fully Met 3b List the milestones that you expect to address over the next 3 years (FY 2006, 2007, and 2008). What do you expect to accomplish, year by year, over the next 3 years under each milestone? FY2006 1. Milestone: Complete photoperiod mapping population development and parental screenings and to create backcross-inbred introgression lines. Anticipated Accomplishment: Further development of the first-of-its-kind population of maize to specifically identify the genetic control of photoperiod. 2. Milestone: Complete genetic mapping of
Fusarium resistance genes. Anticipated Accomplishment: Identify the location of genes for disease resistance on the maize genome map. 3. Milestone: Complete genotyping and phenotyping of stocks used for epistasis mapping. Anticipated Accomplishment: Finalize the germplasm needed for determination of combined-gene effects in maize. 4. Milestone: Complete genotypic and phenotypic evaluation of maize F2:3 populations to determine significant genetic components for agronomically important traits including resistance to corn earworm and relevant maize pathogens. Anticipated Accomplishment: Test the correlation between genetic and visual traits to multiple characteristics. 5. Milestone: Complete generation of F3:4 and F4:5 seed from the 351 maize F2:3 populations of the 27 X 26 half-diallel, and begin to increase the size of populations relevant to the investigation of corn earworm resistance, ethanol production efficiency, and resistance to maize diseases. Anticipated
Accomplishment: Show the effectiveness of specific mapping populations of maize to identify complexly inherited traits in a simple manner. 6. Milestone: Complete multiple-location yield trials of relevant entries from FY 2005 yield trials. Anticipated Accomplishment: Demonstrate the yield potential of newly-developed maize lines as compared to standard hybrids. 7. Milestone: Complete construction of southern leaf blight and gray leaf spot QTL near-isogenic lines. Anticipated Accomplishment: Finish the development of genetically similar lines, which vary only in their response to two diseases. 8. Milestone: Complete QTL mapping in B104 x NC300, A619 x H99, and Ki14 x B73 RIL populations. Anticipated Accomplishment: Finish the development of two maize populations which can be used to identify quantitatively-inherited traits. FY2007 1. Milestone: Complete field and greenhouse phenotyping of photoperiod mapping populations and complete first year of phenotyping of introgression
lines. Anticipated Accomplishment: Show the results of visual characteristics of the first-of-its-kind population of maize to specifically identify the genetic control of photoperiod. 2. Milestone: Identify new sources of resistance to Fusarium ear rot and initiate new mapping populations. Anticipated Accomplishment: Continue with tests to identify both visually and genetically, new forms of disease resistance. 3. Milestone: Identify chromosomal regions interacting at molecular and phenotypic levels. Anticipated Accomplishment: Demonstrate the utility of using molecular approaches to solve maize production problems. 4. Milestone: Complete production of F5:6 seed from 351 maize populations and F6:7 seed from 175 maize populations. Anticipated Accomplishment: Continue with development of new genetic material, which will be used to identify specific genes in maize. 5. Milestone: Complete phenotypic analysis of disease resistance near- isogenic lines. Anticipated Accomplishment:
Show the effectiveness of new sources of resistance to gray leaf spot, southern leaf blight, northern leaf blight, and anthracnose. FY2008 1. Milestone: Complete mapping of photoperiod response genes and favorable genes from exotic maize stocks. Anticipated Accomplishment: Test new genetic material for specific location of photoperiod genes. 2. Milestone: Complete introgression of Fusarium resistance genes into an adapted genetic stock. Anticipated Accomplishment: Show the effectiveness of newly-developed maize lines in controlling disease caused by Fusarium fungus. 3. Milestone: Complete the evaluation of epigenetic components contributing to hybrid vigor in maize. Anticipated Accomplishment: Characterize the specific locations of highly desirable genes in maize in order to make maize breeding more effective. 4. Milestone: Finish screening of 302 lines and determine relationships between maturity and disease resistance. Anticipated Accomplishment: Over 300 maize lines
identified that have improved disease resistance. 4a What was the single most significant accomplishment this past year? Resistance to two corn mycotoxins may be correlated. We discovered that resistance to Fusarium ear rot and fumonisin contamination in corn grain is highly correlated to resistance to Aspergillus ear rot and aflatoxin. This is important because it was previously unknown and demonstrates that at least some mechanisms of resistance to the two ear rots and their associated mycotoxins are in common. This indicates selection for resistance to one ear rot may lead to increased resistance to the other ear rot. Selection for aflatoxin contamination resistance is notoriously difficult and if it is related to fumonisin contamination resistance, we expect that selection for lower fumonisin could lead to both fumonisin and aflatoxin contamination resistances. The outcome of this discovery will be improved breeding methods and corn lines with enhanced resistance to mycotoxin
contamination. 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. Major accomplishments over the life of the project include the identification of semi-tropical maize inbred lines developed from crosses between tropical maize accessions and a temperate-adapted inbred line that produce better hybrids than their temperate parent. Using DNA markers, we demonstrated these lines contain large amounts (at least 30%) of genes from Latin American maize collections, which are not otherwise represented in the USA maize breeding pool. A set of 29 semi-exotic lines with excellent hybrid production capacity that was developed as part of the Germplasm Enhancement of Maize project was publicly released. Another set of lines was tested to evaluate the effectiveness of a new marker-assisted breeding method, the near-isogenic line method. Yield trial results demonstrate that the method is effective at identifying favorable alleles from
donor parents in standard inbred line backgrounds. It was also used to identify gene regions affecting resistance to stress associated with high planting density in corn. A 27 X 26 half-diallel set of crosses between diverse maize inbred lines and derived populations was created for large-scale diversity-based mapping applications. The relationship between genes affecting Fusarium ear rot and fumonisin contamination was clarified, leading to a scientific basis for more efficient breeding programs to improve resistance to these aspects of corn ear rot. Our customers are primarily public and private maize breeders and geneticists. The methods developed have been adopted in other breeding programs, and the released germplasm has been used by other researchers and breeders for genetic mapping studies and applied maize breeding programs. We expect that this will lead to a broader genetic base and enhanced disease resistance for the U.S. corn crop, helping to ensure sustainable
production. This research supports the action plan of NP301. 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The near-isogenic line method of introgressing specific chromosomal segments into a standard genetic background can be adopted by commercial corn breeding programs immediately. Semi-tropical inbred lines are being used by a public maize breeding program in Wisconsin and a new set of semi-exotic lines with improved performance has just been released to the public. The major constraints to the adoption of tropical maize-derived germplasm lines by commercial corn breeding programs is that even the lines that have good yield potential tend to have other agronomic deficiencies, such as poor seed production as inbred lines, poor lodging
resistance, and unfavorable grain moisture characteristics. Nevertheless, such lines will be useful to commercial breeders as parents of new breeding populations.
Impacts
(N/A)
Publications
- Balint Kurti, P.J. 2004. Towards a molecular understanding of mycosphaerella/banana interactions. Book Chapter. p.147-160.
- Szalma, S.J., Buckler Iv, E.S., Snook, M.E., Mcmullen, M.D. 2005. Association analysis of candidate genes for maysin and chlorogenic acid accumulation in maize silks. Journal of Theoretical and Applied Genetics. 110(7):1324-1333.
- Holland, J.B. 2004. Implementation of molecular markers for quantitative traits in a breeding program - challenges and opportunities. In: Fischer, T., et al., editors. New directions for a diverse planet: Proceedings for the 4th International Crop Science Congress. September 26-October 1, 2004. Brisbane, Australia.
- Tarter, J.A., Holland, J.B. 2004. Detecting epistasis through the use of double-introgression near-isogenic lines of maize [abstracts]. Agronomy Abstracts: p.135. Poster No. 195.
- Szalma, S.J. 2005. Diversity-based approaches to exploring genetic phenomena and quantitative traits in maize [abstract]. Maize Genetics Conference.
- Robertson, L.A., Kleinschmidt, C.E., White, D.G., Payne, G.A., Holland, J. B. 2004. Genetic correlations and heritability of fusarium ear rot resistance and fumonisin contamination resistance in two maize populations [abstract].American Society of Agronomy.
- Briggs, W., Buckler Iv, E.S., Canaran, P., Doebley, J., Fulton, T., Gaut, B., Goodman, M., Holland, J.B., Kresovich, S., Mcmullen, M.D., Stein, L., Ware, D., Wright, S., Zhao, W. 2005. Molecular and functional diversity in the maize genome [abstract]. Maize Genetics Conference. Paper No. 177. p. 126.
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Progress 10/01/03 to 09/30/04
Outputs
1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter? The genetic base of U.S. field corn is narrow relative to the total genetic diversity available in the species worldwide. The limited genetic base of U.S. corn may leave the crop susceptible to newly evolved strains of pathogens and it may limit breeding gains for important agronomic traits. This project has three main objectives, all related to broadening the genetic base of the U.S. corn crop by identifying favorable genes in exotic genetic resources and creating genomics- assisted breeding techniques to incorporate them into the U.S. maize gene pool. One objective is to identify chromosomal regions at which exotic maize lines possess genes with agronomic effects superior to those carried in Corn Belt lines. At the same time, the exotic gene regions that cause photoperiod sensitivity, the major
problem of adaptation of tropical corn to U.S. growing environments, will be mapped. This will permit rapid elimination of these unfavorable genes when introducing tropical maize germplasm into Corn Belt populations. The second objective is to identify sources of resistance to Fusarium ear rot disease and accumulation of the mycotoxin fumonisin, map the genes conferring resistance, and combine multiple resistance genes into a single breeding line. The third objective is to characterize the frequency and importance of gene interactions ("epistasis") on agronomically important traits of varying complexity. If a gene's effect depends on the presence of specific forms of other genes in the genetic background, then epistasis is important, and DNA marker-assisted selection and exotic germplasm breeding schemes will require modification to exploit this genetic phenomenon. Potential impact of the work is the creation of improved corn lines that can improve the productivity and disease
resistance of hybrids grown by farmers. 2. List the milestones (indicators of progress) from your Project Plan. Year 1 (FY 2004) Complete greenhouse evaluations of photoperiod-sensitive and insensitive lines and backcross ("introgress") exotic lines to a standard temperate line two generations. Complete 2nd year of phenotypic evaluations for Fusarium/fumonisin resistance. Complete development of genetic stocks with pairs of introgressed chromosome segments to test epistasis. Year 2 (FY 2005) Complete photoperiod mapping population development and parental screenings and to create backcross-inbred introgression lines. Complete genetic mapping of Fusarium resistance genes. Complete genotyping and phenotyping of stocks used for epistasis mapping. Year 3 (FY 2006) Complete field and greenhouse phenotyping of photoperiod mapping populations and complete first year of phenotyping of introgression lines. Identify new sources of resistance to Fusarium ear rot and initiate new mapping
populations. Identify chromosomal regions interacting at molecular and phenotypic levels. Year 4 (FY 2007) Complete mapping of photoperiod response genes and favorable genes from exotic maize stocks Complete introgression of Fusarium resistance genes into an adapted genetic stock. Release superior genetic stocks with two introgressions. 3. Milestones: A. Milestones expected to be reached in FY2004 were the 14-month milestones: to (1) complete greenhouse evaluations of photoperiod- sensitive and insensitive lines and create BC2F2 introgression lines, (2) complete 2nd year of phenotypic evaluations for Fusarium/fumonisin resistance, and (3) complete development of genetic stocks with pairs of introgressed chromosome segments to test epistasis. All milestones have been fully met. B. Milestones expected to be reached in FY2005 are same as for FY2004. Thus, we are ahead of schedule on all projects. Milestones expected to be reached in FY2006 are the 32-month milestones: to (1) complete
photoperiod mapping population development and parental screenings and to create backcross-inbred introgression lines, (2) complete genetic mapping of Fusarium resistance genes, and (3) complete genotyping and phenotyping of stocks used for epistasis mapping. Milestones expected to be reached in FY2007 are the 48-month milestones: to (1) complete field and greenhouse phenotyping of photoperiod mapping populations and complete first year of phenotyping of introgression lines, (2) identify new sources of resistance to Fusarium ear rot and initiate new mapping populations, and (3) identify chromosomal regions interacting at molecular and phenotypic levels. 4. What were the most significant accomplishments this past year? A. Single Most Significant Accomplishment During FY 2004: We discovered that resistance to fumonisin contamination in corn grain is highly heritable and is also highly genetically correlated to resistance to Fusarium ear rot. This is important because it was previously
unknown and demonstrates that the resistance traits can be accurately characterized in field evaluations (if careful inoculating procedures are followed). This indicates that we should be successful at identifying the underlying resistance genes and also that selection on phenotypes should also be effective at improving these resistance traits. After completing two years of field trials of two populations segregating for Fusarium resistance, we discovered that at least 75% of the phenotypic variation between corn lines for fumonisin contamination was due to genetic effects, and that these genetic effects had a correlation of at least 87% with ear rot symptoms. This work was conducted in collaboration with North Carolina State University, the University of Illinois, and the Mycotoxin Research unit at the USDA-ARS National Center for Agricultural Utilization Research in Peoria, IL. The outcome of this discovery will be improved breeding methods and corn lines with enhanced resistance
to mycotoxin contamination. B. Other Significant Accomplishments During FY 2004: None. C. Significant activities that support special target populations. None. 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. Major accomplishments over the life of the project include the identification of semi-tropical maize inbred lines developed from crosses between tropical maize accessions and a temperate-adapted inbred line that produce better hybrids than their temperate parent. Using DNA markers, we demonstrated these lines contain large amounts (at least 30%) of genes from Latin American maize collections, which are not otherwise represented in the USA maize breeding pool. Another set of lines was tested to evaluate the effectiveness of a new marker-assisted breeding method, the near-isogenic line method. Yield trial results demonstrate that the method is effective at identifying favorable alleles from donor parents in standard
inbred line backgrounds. It was also used to identify gene regions affecting resistance to stress associated with high planting density in corn. 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The near-isogenic line method of introgressing specific chromosomal segments into a standard genetic background can be adopted by commercial corn breeding programs immediately. Semi-tropical inbred lines are being used by a public maize breeding program in Wisconsin. The major constraints to the adoption of tropical maize-derived germplasm lines by commercial corn breeding programs is that even the lines that have good yield potential tend to have other agronomic deficiencies, such as poor seed production as inbred lines, poor lodging resistance, and
unfavorable grain moisture characteristics. Nevertheless, such lines will be useful to commercial breeders as parents of new breeding populations.
Impacts
(N/A)
Publications
- HOLLAND, J.B. INCORPORATION OF EXOTIC GERMPLASM. ENCYCLOPEDIA OF PLANT & CROP SCIENCE. 2004.
- HELLAND, S.J., HOLLAND, J.B. GENOME-WIDE GENETIC DIVERSITY AMONG COMPONENTS DOES NOT CAUSE CULTIVAR BLEND RESPONSES. CROP SCIENCE.
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