Source: UNIV OF MINNESOTA submitted to
GENOMEWIDE SELECTION TO INTROGRESS EXOTIC DWARF-CORN GERMPLASM INTO U.S. CORN BELT GERMPLASM
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
0218944
Grant No.
2009-65300-05637
Project No.
MIN-13-G18
Proposal No.
2009-01884
Multistate No.
(N/A)
Program Code
91610
Project Start Date
Sep 1, 2009
Project End Date
Aug 31, 2013
Grant Year
2009
Project Director
Bernardo, R.
Recipient Organization
UNIV OF MINNESOTA
(N/A)
ST PAUL,MN 55108
Performing Department
Agronomy & Plant Genetics
Non Technical Summary
Corn is the major crop in the U.S., with 275 million metric tons of grain harvested each year for feed, food, bioenergy, and industrial uses. Grain yields per hectare in the U.S. have increased by 300% since the 1950s. Future increases in corn productivity depend on improved cultural practices, expanded areas for production, and genetically superior corn hybrids. Dwarf corn can be grown at twice the plant population densities currently used in production, and it matures much earlier than current U.S. Corn Belt hybrids but has lower grain yields. This research aims to exploit cheap and abundant DNA fingerprints to rapidly combine useful traits from dwarf corn and from U.S. corn. This research may contribute to the long-range improvement and sustainability of U.S. agriculture in three ways. First, introducing early-maturity, dwarf-corn strains into U.S. hybrid corn could expand northward the area of adaptation of U.S. corn or allow corn to fit in new crop rotation patterns. Second, this different plant type may enhance both the productivity of and ecosystem services from U.S. corn. Third, the research will evaluate a selection method that, if proved useful, can be used by breeders to eventually introduce other types of exotic germplasm into U.S. corn.
Animal Health Component
(N/A)
Research Effort Categories
Basic
25%
Applied
50%
Developmental
25%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2021510108150%
2011510108050%
Knowledge Area
202 - Plant Genetic Resources; 201 - Plant Genome, Genetics, and Genetic Mechanisms;

Subject Of Investigation
1510 - Corn;

Field Of Science
1080 - Genetics; 1081 - Breeding;
Goals / Objectives
This research will determine if selection methods that exploit cheap and abundant molecular markers are useful for combining useful traits from exotic dwarf-corn germplasm with the high productivity of U.S. Corn Belt germplasm. Specifically, this research aims to: (1) determine if the high grain yield of non-dwarf corn can be combined with the reduced stature and adaptability to high plant population densities of dwarf corn; (2) develop, to the extent possible, corn germplasm that combines such traits; and (3) determine if, as indicated by theoretical studies, genomewide selection is useful for the rapid improvement of an adapted x exotic cross for multiple traits. Outputs from this project would therefore include increased knowledge about the usefulness of a dwarf plant type for hybrid corn and about the usefulness of molecular markers for exploiting exotic germplasm, as well as improved germplasm with enhanced genetic diversity.
Project Methods
Two dwarf corn x U.S. corn crosses will be bred for high grain yield, good standability, reduced stature, and adaptation to high plant population densities. In addition, one population will be bred for later maturity and the other will be bred for earlier maturity. Genomewide selection, a seemingly counterintuitive procedure that circumvents the need to first identify molecular markers associated with the target traits, will be used to improve the dwarf corn x U.S. corn crosses. Phenotypic and marker data for the two crosses shall be used to construct genomewide prediction models for different traits. Selection based on molecular markers only will be conducted in a year-round greenhouse in an attempt to rapidly improve the crosses. In addition, the dwarfing trait will be introgressed via phenotypic backcrossing into the non-dwarf parents. This will allow a comparison of the gains that may be achieved by simply introgressing genes for plant architecture versus by genomewide selection for both plant architecture and background genes that affect yield and agronomic performance.

Progress 09/01/09 to 08/31/13

Outputs
Target Audience: The target audience included plant breeders in the seed industry, and professors and graduate students at different universities in the U.S. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Dr. Emily Combs developed her Ph.D. dissertaion under this grant and earned her doctoral degree in plant breeding/molecular genetics at the University of Minnesota in January 2014. The Project Director organized a short course on "Marker-Assisted Plant Breeding" held on 5-8 June 2012 at the University of Minnesota. This short course was very well received by 60 participants, to the extent that the short course will now be held every two years in Saint Paul. How have the results been disseminated to communities of interest? The results of our research have been disseminated through 3 peer-reviewed journal publications and 2 conference presentations. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? All of the stated goals were accomplished. We found that unfavorable genetic correlations made it difficult to select for short plants with high grain yield. Nevertheless, genomewide selection was more effective than traditional phenotypic backcrossing for improving mean performance for multiple traits and for introgressing a high proportion of exotic germplasm into adapted material. To our knowledge, our study was the first reported experiment on the use of genomewide selection to improve an adapted x exotic cross. In addition, we found that increasing the population size, heritability of the trait, and number of markers increased the accuracy of genomewide prediction. However, different traits within the same breeding population differed in their prediction accuracy even when population size, heritability, and number of markers were kept constant. This result indicated that traits inherently differ in their prediction accuracy and that empirical data are needed to assess which traits are more predictable than others. Finally, some traits such as plant height may be controlled by the joint effects of known major genes and unknown background genes. We found that explicitly modeling the effects of known major genes is helpful in genomewide selection.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Combs, E., and R. Bernardo. 2013. Accuracy of genomewide selection for different traits with constant population Size, heritability, and number of markers. The Plant Genome doi: 10.3835/plantgenome2012.11.0030.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Combs, E., and R. Bernardo. 2013. Genomewide selection to introgress semidwarf corn germplasm into U.S. Corn Belt inbreds. Crop Sci. 53: 1427-1436.
  • Type: Journal Articles Status: Under Review Year Published: 2014 Citation: Bernardo, R. 2014. Genomewide selection when major genes are present. Crop Science (tentatively accepted).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2012 Citation: Bernardo, R. 2012. Lessons from genomewide selection in agronomic crops. 15th European Assoc. Plant Breed. Res. (EUCARPIA) Biometrics in Plant Breed. Section Mtg., 5-7 Sept. 2012, Stuttgart, Germany.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2012 Citation: Combs, E., and R. Bernardo. 2012. Joint effects of population size, marker density, heritability, and trait per se on accuracy of genomewide predictions in biparental populations. NCCC167 North Central Reg. Corn Breed. Res. Mtg., 14-15 March 2012, Portland, OR.


Progress 09/01/11 to 08/31/12

Outputs
OUTPUTS: The outputs from this project comprised (i) information on the genetics and inheritance of the dwarfing trait in semidwarf corn line; (ii) DNA markers associated with the dwarfing trait; (iii) information on the usefulness of genomewide selection for introgressing exotic germplasm into adapted corn; and (iv) corn germplasm with short stature and improved performance for grain yield and agronomic traits. PARTICIPANTS: Dr. Rex Bernardo provided expertise on statistical genetic models for utilizing cheap and abundant DNA markers in corn breeding. Ms. Emily Combs is a University of Minnesota Ph.D. student whose thesis research focuses on marker-based selection to introgress the dwarfing trait from exotic germplasm into adapted germplasm. TARGET AUDIENCES: Target audiences include corn breeders who seek to apply DNA marker technologies in corn improvement, and agronomists and corn producers interested in dwarf-corn hybrids that could fit new cropping systems or be planted in areas with a very short growing season. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The per-generation gain was greater with phenoptypic selection than with genomewide selection. While phenotypic selection led to an increase in grain yield, it also led to an unwanted increase in plant height. The strong negative genetic correlation between plant height and grain yield would impede progress in breeding for both traits regardless of whether breeding is by phenotypic selection or genomewide selection. Nevertheless, our results in one of two adapted x exotic crosses we studied suggested that genomewide selection may enable gains for plant height while holding grain yield and agronomic traits constant. Furthermore, mean performance across different traits was better with genomewide selection than with simple phenotypic backcrossing of the dwarfing trait. The best generations of selection began to combine dwarf stature with acceptable grain yield and agronomic performance.

Publications

  • Bernardo, R. 2012. Lessons from genomewide prediction and selection in maize. 15th European Association for Plant Breeding Research (EUCARPIA)-Biometrics in Plant Breeding Section Conf., 5-7 September 2012, Stuttgart, Germany.


Progress 09/01/10 to 08/31/11

Outputs
OUTPUTS: The outputs from this project comprised (i) information on the genetics and inheritance of the dwarfing trait in an improved Canadian dwarf-corn population; (ii) DNA markers associated with the dwarfing trait; (iii) prediction equations that allow the selection of dwarf x adapted corn for grain yield, plant height, and other agronomic traits; and (iv) corn germplasm currently being selected based on DNA markers for these traits. PARTICIPANTS: Dr. Rex Bernardo provided expertise on statistical genetic models for utilizing cheap and abundant DNA markers in corn breeding. Ms. Emily Combs is a University of Minnesota Ph.D. student whose thesis research focuses on marker-based selection to introgress the dwarfing trait from exotic germplasm into adapted germplasm. TARGET AUDIENCES: Target audiences include corn breeders who seek to apply DNA marker technologies in corn improvement, and agronomists and corn producers interested in dwarf-corn hybrids that could fit new cropping systems or be planted in areas with a very short growing season. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Taller corn plants generally have higher grain yields than shorter plants. Our cycle 0 results suggest that this general relationship is not necessarily true in dwarf-corn germplasm: our cycle 0 selections for one population combined high yields and shorter plant statures. Predicted responses to four cycles of selection, based purely on DNA markers, indicate anticipated reductions (compared with cycle 0) in plant height of 20 cm and increases in grain yield of 0.5-0.6 t/ha. We look forward to discovering, based on 2012 field trials, how well the observed responses correspond with these predicted responses.

Publications

  • Combs, E.E., and Bernardo, R. 2011. Genomewide selection to introgress exotic dwarf-corn germplasm into U.S. corn belt germplasm. 53rd Annu. Maize Genet. Conf., 17-20 Mar. 2011, Saint Charles, IL.


Progress 09/01/09 to 08/31/10

Outputs
OUTPUTS: The outputs from this project comprised (i) a talk at a conference of industry corn breeders in Illinois; (ii) a talk at a conference of pig producers interested in the latest developments in plant breeding; (iii) a seminar presentation in the Department of Agronomy and Plant Genetics, University of Minnesota; and (iv) corn germplasm selected for grain yield, agronomic performance, and dwarf stature. While the cycle 0 genotypic and phenotypic data are now available for the dwarf x non-dwarf crosses, these data will be deposited in MaizeGDB when data from succeeding cycles of marker-based selection also become available in 2012. The cycle 0 data, however, are available from the PD upon request. PARTICIPANTS: Combs, Emily. Ph.D. Applied Plant Sciences (Plant Breeding/Molecular Genetics), Univ. of Minnesota, 2009-present. The research described herein comprises Ms. Combs's Ph.D. dissertation. TARGET AUDIENCES: The target audiences include corn producers who might benefit from information on the potential benefits of a dwarf-corn plant type, and plant breeders who can utilize our results on the use of molecular markers to introgress exotic germplasm into elite lines. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Taller corn plants generally have higher grain yields than shorter plants. Our cycle 0 results suggest that this general relationship is not necessarily true in dwarf-corn germplasm: our cycle 0 selections for one population combined high yields and shorter plant statures. Compared with the commercial check hybrids, however, the selected F3 families in cycle 0 suffered a 30-45% penalty in yield performance. We look forward to discovering how much of this dwarf-corn yield penalty could be overcome by genomewide selection. Overall, we anticipate validating a marker-assisted selection method that would allow the rapid introgression of useful traits from other kinds of diverse, exotic germplasm into U.S. corn.

Publications

  • Bernardo, R., R.E. Lorenzana, and P.J. Mayor. 2010. Exploiting both doubled haploids and cheap and abundant molecular markers in corn breeding. Illinois Corn Breeders School, 1-2 March 2010, Urbana, IL.