Location: Corn Insects and Crop Genetics Research
2023 Annual Report
Objectives
Objective 1: Develop improved maize phenotyping methods based on process-based crop growth models and high throughput phenotyping methods.
Subobjective 1.1: Develop and validate crop growth model calibrations for diverse maize hybrids to predict maize hybrid performance across diverse environments.
Subobjective 1.2: Evaluate high throughput biochemical and metabolic assays for calibration of crop growth models and prediction of maize grain yield.
Subobjective 1.3: Evaluate remote sensing approaches for improving prediction of maize performance and crop growth model calibration.
Objective 2: Understand the molecular genetic control of gametophytic incompatibility.
Subobjective 2.1: Determine if ZmPme3 complements the ga1 allele to restore the female function of Ga1-s.
Subobjective 2.2: Determine the biochemical mechanism of pollen exclusion by the Ga1 system using E. coli expressed ZmPME3.
Subobjective 2.3: Identify binding partners of ZmPME3.
Approach
In order to used hybrid-specific crop growth models to understand factors contributing to genotype by environment interactions, replicated field trials of hybrid corn varieties will be carried out and evaluated for morphological, phonological and chemical traits. Together with environmental data, these data will be used to develop crop growth models with publicly available software. Valuable measures of agronomic performance such as grain yield of the specific hybrids in the study will be predicted. These models will be validated using actual measurements of agronomic performance and used to predict performance in additional environmental conditions. In order to understand to molecular genetic control mechanism of gametophytic incompatibility, we will construct a transgene encoding ZmPME3 and use it to complement the ga1 phenotype. A second transgene will be used to mutationally inactivate ZmPME3. All transgenic lines will be evaluated for their ability to exclude unwanted pollen in replicated field trials. In addition, ZmPME will be produced in a bacterial expression system and purified. The activity of the purified protein will be characterized using pectin methylesterase activity assays and the effect of this protein on pollen tube growth will be evaluated in vitro.
Progress Report
As part of a cooperative agreement with the Iowa Corn Promotion Board, we evaluated diverse maize hybrids at four Iowa locations in the 2022 growing season. Data were collected on nine agronomic traits. Agronomic data in addition to weather data and management data were submitted to the Genomes to Fields (G2F) Initiative. The G2F initiative is a multi-state, multi-institution initiative designed to foster collaboration and improve understanding of genomic control of complex traits. Collaborators in G2F grew diverse hybrids across many diverse environments to understand how diverse hybrids perform across a range of very different environments. The work is continuing with diverse hybrids again planted in four locations in 2023.
As part of a collaboration with scientists from Brigham Young University, we evaluated 64 maize hybrids with widely varying stalk strength. The hybrids were planted in two Iowa locations at three plant densities. Stalk strength was tested using experimental devices developed by scientists at Brigham Young University. The devices measure the amount of force needed to both bend and break a maize stalk. The force needed to bend stalks was highly correlated with the force needed to physically break the stalk. In addition, measurements were highly correlated between plant densities and environments. Repeatability of both measurements (bending and breaking) was 0.85 and higher in all instances.
Crop model calibrations have been developed for twelve maize hybrids as part of Objective 1 of the project plan. The calibrations were thoroughly tested through a rigorous process that included iterative model building and sensitivity analysis. The calibrations that were obtained allowed us to evaluate potential areas for model improvement (most notably to excess soil water), to test the ability of models to predict genotype by environment interaction, and to determine how climate change will impact breeding targets. Calibrations will be publicly available providing other researchers access to model calibrations for publicly available hybrids.
Comparison of pollen exclusion in field corn and popcorn. As part of Objective 2 of our project plan (Understand molecular genetic control of gametophytic incompatibility) we completed experiments comparing the ability of field corn and popcorn to exclude pollen when carrying the Ga1-s allele. Ga1-S can be used in production systems to exclude unwanted pollen, for example, it can prevent pollen from a genetically modified organism from contaminating organic corn fields, or field corn from contaminating popcorn. Preliminary analysis indicates that field corn can exclude pollen as well as popcorn, however variation in field corn necessitates testing of each hybrid to ensure that pollen exclusion is effective.
Elucidating the genomic context of the Ga1 Locus. The following work was carried out as part of Objective 2 of our project plan (Understand molecular genetic control of gametophytic incompatibility). The Ga1 genetic locus in maize controls the ability of maize to produce grain, a trait called cross incompatibility. A large segment of the genome surrounding this locus contains inactive genes (pseudogenes) that are related to the active genes at the Ga1 locus. In collaboration with scientists from Iowa State University, we initiated a new computational project to analyze the genome structure around the Ga1 locus in 20 diverse varieties including the popcorn variety HP301. This allowed us to identify structural differences between genomes and analyze the phylogenetic relationships among pseudogenes in varieties with different structures.
This work advanced our ability to predict performance of corn varieties in different production environments. This will help plant breeders develop new varieties with better performance. Seed companies will be able to make better variety recommendations, leading to increased production and reduced risk for corn growers. This work also led to a better understanding of the genetic control of gametophytic incompatibility systems such as the Ga1 system in corn. Scientists and breeders will use this information to develop improved strategies for increasing the genetic purity of specialty corn, reducing risk of contamination and costs of maintaining genetic purity. Beneficiaries include specialty corn producers and consumers.
Accomplishments
1. Similar genetics will support productivity gains and climate resilience in maize. Continued increases in maize productivity will be needed to support increasing demand. Changes in climate will require maize hybrids with different characteristics to maintain and increase productivity. Researchers in Ames, Iowa, used a modeling approach to predict how maize hybrids might need to be changed in response to changes in climate. The changes in hybrid characteristics needed to sustain increases in productivity were found to be very similar to the changes needed to sustain increases in the current climate. This research is significant because it demonstrates that similar breeding approaches and genetics will enable us to sustain productivity increases in the face of a changing climate which will inform breeders on how to adapt breeding programs for future genetic gain.
Review Publications
Winn, C.A., Archontoulis, S.V., Edwards, J.W. 2023. Calibration of a crop growth model in APSIM for 15 publicly available corn hybrids in North America. Crop Science. 63(2): 511-534. https://doi.org/10.1002/csc2.20857.
Moran Lauter, A., Edwards, J.W., Scott, M.P. 2022. The maize Ga1-s allele confers protection against ga1 pollen in popcorn and dent corn. Scientific Reports. 12. Article 20809. https://doi.org/10.1038/s41598-022-25261-8.
Hintch, T., Moran Lauter, A., Kinney, S., Lubberstedt, T., Frei, U., Duangpapeng, P., Edwards, J.W., Scott, M.P. 2023. Development of maize inbred lines with elevated grain methionine concentration from a high methionine population. Crop Science. https://doi.org/10.1002/csc2.20983.
