LONG-TERM SELECTION OF CORN FOR OIL AND PROTEIN CONTENT

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1019279
• Project Start Date: Apr 1, 2019
• Project End Date: Sep 30, 2023
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF ILLINOIS
2001 S. Lincoln Ave.
URBANA,IL 61801

Performing Department
Crop Sciences

Non Technical Summary
The grain of maize has many uses, due in part to its tremendous diversity of grain compositions. Grain composition is highly heritable, and breeding has created many specialized grain compositions with high commercial value, such as Illini SuperSweet corn and high oil hybrids. The Illinois Long-term Selection Experiment (ILTSE) was initiated in 1896, and has completed more than 900 cycles of directed selection for protein and oil concentration in maize grain. The ILTSE has created populations with the known genetic extremes for kernel composition and a number of associated traits, such as nitrogen uptake and utilization, seed development, and grain yield. The long history of genetic isolation coupled with intensive selection suggests the ILTSE likely harbors unique genetic variants not currently present in elite germplasm. Investigating the genomic control of the phenotypic variation in the ILTSE will discover genes that contribute to the economic value of maize, and offer new insights into evolutionary biology and its response to human selection. The ILTSE is also a valuable germplasm resource, and knowledge gained from its continued study can then be applied to maize improvement through molecular breeding, biotechnology, or genome editing approaches.

Animal Health Component

100%

Research Effort Categories

Basic

0%

Applied

100%

Developmental

0%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
203	1510	1080	100%

Knowledge Area
203 - Plant Biological Efficiency and Abiotic Stresses Affecting Plants;

Subject Of Investigation
1510 - Corn;

Field Of Science
1080 - Genetics;

Keywords

maize

oil content

illinois long-term selection experiment

protein content

phenotypic extremes

Goals / Objectives
1. Continue selection in IHP, IRLP, IRLP2, IRHP2 and IRHP3.2. Maintain the ILTSE germplasm resource by refreshing seed of archived populations.3. Create new genetic materials from the ILTSE to facilitate gene discovery and maize genetic improvement.

Project Methods
Objective 1: Continue selection in IHP, IRLP, IRLP2, IRHP2 and IRHP3.These five populations will be grown each summer at the University of Illinois. The breeding scheme is the same as has been practiced since 1965. For each population, 300 seeds are planted, 100 ears are generated from sib mating and each plant is used only once as a parent. As controls, the inbred lines from each of the ILTSE genotypes are also grown. Mature ears are harvested, shelled, and their grain composition estimated by Near Infrared Reflectance (NIR) using the Perten DA7200 instrument and a custom calibration for maize grain composition that includes samples from the ILTSE. Depending on genotype, the twelve ears with the highest or lowest protein concentration will be selected as the parents of the next cycle of recurrent selection. The remaining seed is saved as an archive for five years.Objective 2: Maintain the ILTSE germplasm resource by refreshing seed of archived populations.Archiving seed for each cycle of selection from each population would require substantial seed storage space. Furthermore, the seed viability of older cycles declines even when stored under ideal conditions. To maintain the ILTSE germplasm resource, seed is archived from the oldest cycle available, and every tenth cycle thereafter until the most recent or final cycle. For example, cycles 65, 75, 85, 95, 105, 115 and 118 are archived for IHP. In total, there are currently 52 cycles to maintain. Because seed stored properly remains viable for 20 years, once archived seed is 20 years old, that population will be grown and ears created as described above for Objective 1, refreshing the seed while maintaining the genetic variation in the population. Objective 3: Create new genetic materials from the ILTSE to facilitate gene discovery and maize genetic improvement.The large range of differences for economically important traits in the ILTSE, coupled with high density genotyping, makes it possible to identify DNA variations that are associated with these traits. We will employ both linkage mapping in the IPSRIs and genome-wide association studies (GWAS) in the ILTSE. When such associations are found, it is often necessary to conduct additional breeding experiments to demonstrate their benefits, such as crosses with other germplasm to demonstrate transfer of the trait. There are also opportunities to create novel combinations of traits for specific end uses, such as the hybrids with higher value by-products from ethanol processing. Finally, although the ILTSE likely harbors novel beneficial genetic variants, the poor grain yield and agronomic performance of the germplasm limits its direct use. Applying modern approaches to germplasm improvement of the ILTSE, such as genomic selection using models trained on grain yield performance in the ILTSE or other maize populations, could rapidly upgrade its agronomic performance.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Scientists engaged in studies of plant evolution, genetics, and breeding. Researchers with interest in trait variation modulated by the experiment, such as grain composition and nutrient utilization. Users of corn with novel grain compositions. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project provides practical training to undergraduate and graduate students in the genetic improvement of corn, specifically grain composition and related traits, such as N utilization. How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?Conduct an additional cycle of selection for grain composition traits in the populations selected for grain protein concentration. Continue creation of near-isogenic lines among the different Illinois Protein Strains. Evaluate additional hybrids with the ILO3 low oil parent. Evaluate agronomic performance of improved inbreds and hybrids derived from the Illinois Protein Strains Recombinant Inbred Lines.

Impacts
What was accomplished under these goals? An additional cycle of selection was conducted for each of IHP, IRLP, IRLP2, IRHP2, and IRHP3. Because selection progress has stopped in the original Illinois Reverse High Protein (IRHP) after 64 cycles of selection, one representative ear was planted in 2020 to begin inbreeding a stable line. To monitor environmental impacts on phenotypes, we also grew inbred lines derived from selected populations: IHP1, ILP1, IHO2, Illinois Switchback High Oil (ISHO), Illinois Reverse High Oil (IRHO), and Illinois Reverse Low Oil (IRLO). Grain composition was measured for at least 60 ears from each of these populations, using near-infrared reflectance and a custom calibration on a Perten DA7200 instrument. A fifth generation of backcrossing was conducted to create populations of near-isogenic lines among the different Illinois Protein Strains, as a resource that will facilitate future fine-mapping and functional validation of genes contributing to the variation in grain protein concentration. Four such populations are being developed: IHP1 introgression into the IRHP1 background, IHP1 introgression into the ILP1 background, IRLP1 introgression into the ILP1 background, and ILP1 introgression into the IRLP1 background. For each population, the recurrent parent is a near-isogenic line that carries the FLOURY2-RFP (FL2-RFP) transgene, which is an easily scored visual marker for alpha-zein gene expression. From each BC3 family grown in 2019, 5 BC4 ears were produced. All BC4 ears were photographed and visual selections for intensity of FL2-RFP expression were made in each population. Grain protein concentration was also measured for each ear using NIR. The combination of FL2-RFP RFP intensity and grain protein concentration was used to select the ear in each BC4 family that differed the greatest from its recurrent parent. This BC4 ear was planted for the next generation of backcrossing. Interest from a local brewer has prompted an evaluation of the Illinois Low Oil for brewing. Because of the higher yield and agronomics of hybrids, hybrids between Illinois Low Oil and Illinois Low Protein were produced and evaluated. The ILO3 inbred line was measured as having 2% oil, and crossing of ILO3 to ILP1 produced hybrids that in small plots yielded approximately 100 bushels per acre and 2-3% oil.

Publications

Progress 04/01/19 to 09/30/19

Outputs
Target Audience:Scientists engaged in studies of plant evolution, genetics, and breeding. Researchers with interests in trait variation modulated by the experiment, such as grain composition and nutrient utilization. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project provides practical training to undergraduate and graduate students in the genetic improvement of corn, specifically grain composition and related traits, such as nitrogen utilization. How have the results been disseminated to communities of interest?Through presentations at scientific conferences, seminars, and peer-reviewed publications. What do you plan to do during the next reporting period to accomplish the goals?Conduct an additional cycle of selection for grain composition traits in the populations selected for grain protein concentration. Continue the creation of reciprocal near-isogenic lines among the Illinois Protein Selection inbreds. Publish journal articles on results from experiments using the Illinois Long Term Selection experiment materials.

Impacts
What was accomplished under these goals? An additional cycle of selection was conducted in 2019 for each of IHP, IRLP, IRLP2, IRHP2, and IRHP3. Grain composition will be measured for at least 60 ears from each of these populations, using a Perten DA7200 NIR instrument. To monitor environmental impacts on phenotypes, the following eightinbred lines derived from other selected populations were grown in plots adjacent to the ongoing selection experiments: IHP1, ILP1, IHO2, ILO2, ILO3, Illinois Switchback High Oil (ISHO), Illinois Reverse High Oil (IRHO), and Illinois Reverse Low Oil (IRLO). Data collection is in progress, so 2019 results will be made available in the 2020 report. A fifth generation of backcrossing was conducted to create populations of near-isogenic lines among the different Illinois Protein Strains, as a resource that will facilitate future fine-mapping and functional validation of genes contributing to the variation in grain protein concentration. Four such populations are being developed: IHP1 introgression into the IRHP1 background, IHP1 introgression into the ILP1 background, IRLP1 introgression into the ILP1 background, and ILP1 introgression into the IRLP1 background. For each population, the recurrent parent is a near-isogenic line that carries the FLOURY2-RFP (FL2-RFP) transgene, which is an easily scored visual marker for alpha-zein gene expression. Alpha-zeins are the most abundant seed storage protein in maize kernels, and their accumulation has been altered by the selection experiment. From each BC3 family grown in 2018, five BC4 ears were produced. All BC4 ears will be photographed and visual selections for intensity of FL2-RFP expression will be made in each population. The ear with strongest FL2-RFP intensity in each BC4 family will be selected for the populations where IHP1 is being introgressed into either ILP1 or IRHP1, and the same for IRLP1 introgressions into ILP1. Conversely, the ear with the weakest FL2-RFP intensity will be selected for the population where ILP1 is being introgressed into IRLP1. A collaboration with scientists from Corteva Agrisciences (formerly Pioneer-DuPont) led to the discovery of a novel genetic variant in the ILP1 inbred line that delays leaf senescence. Reduced expression of the NAC7 transcription factor in ILP1 conditioned a staygreen phenotype, and production of transgenic maize lines with reduced expression of NAC7 in elite inbred and hybrid backgrounds also conditioned a staygreen phenotype and yield increases in multi-location field trials. These findings were reported in Zhang et al. (2019 Plant Biotechnology Journal DOI: 10.1111/pbi.13139). We had previously produced inbred lines where mutations expected to increase the essential amino acids lysine and tryptophan were introgressed into the Illinois Protein strains backgrounds, as well as the FR1064 (an elite Stiff-Stalk inbred) and Mo17 (a non- Stiff Stalk inbred). It was hypothesized that the dried distillers grains (DDGS) co-product produced from processing to ethanol would have elevated levels of lysine and tryptophan, and thus higher value in animal feed. Through collaboration with University of Illinois faculty Dr. Vijay Singh in the Department Agricultural and Biological Engineering and Dr. Carl Parsons in the Department of Animal Sciences, we demonstrated that the DDGS indeed contained higher levels of lysine, tryptophan, and other essential amino acids. These DDGS were also found to be effectively metabolized by chickens, indicating their potential as an animal feed. These findings were published in Corray et al. (2019, Poultry Science).

Publications

• Type: Journal Articles Status: Published Year Published: 2019 Citation: Zhang, J., Fengler, K., Hemert, J., Gupta, R., Mongar, N., Sun, J., Allen, W., Wang, Y., Weers, B., Mo, H., Lafitte, R., Hou, Z., Bryant, A., Ibraheem, F., Arp, J., Swaminathan, K., Moose, S., Li, B. and Shen, B. 2019. Identification and characterization of nac7, a novel stay-green QTL, that increases yield in maize. Plant Biotechnology Journal DOI: 10.1111/pbi.13139.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Corray, S., Utterback, P., Ramchandran, D., Singh, V., Moose, S.P. and Parsons, C.M. 2018. Nutritional evaluation of three types of novel ethanol coproducts. Poultry Science 98: 2933-2939.