Research Project: Management, Utilization, and Distribution of Maize Genetic Stocks and Associated Descriptive Information

Location: Soybean/maize Germplasm, Pathology, and Genetics Research

2025 Annual Report

Objectives
Objective 1: Conduct research to develop genetic resource maintenance, evaluation, or characterization methods and, in alignment with the overall NPGS Plan, then apply them to avoid backlogs in maize genetic stock and information management. Objective 2: Acquire, distribute, and maintain the safety, genetic integrity, health, and viability of maize genetic stocks and associated descriptive information.

Approach
We will phenotype maize genetic stocks to ensure their identity and trueness-to-type. For newly acquired stocks for which molecular data are available, we will work with submitters to confirm the presence of molecular phenotypes within increased materials. Kernel and ear traits will be evaluated on the cob and after the seeds have been shelled. Seedling traits will be evaluated in sand benches and shortly after germination in the field. Adult plant traits will be evaluated in an observation field. If homozygous viable, mutant plants will be marked for increase and these can be self- or sib-pollinated to generate seeds homozygous for the mutant. Unique quality control processes will be developed for novel stock types and traits. These processes will be customized to address the challenges that emerge, including procedures to avoid backlogs. Lethal recessive traits must be maintained as heterozygotes and screened each generation to determine which F2 ears carry the mutant trait. We will use appropriate conservation tools to maintain our genetic stock collection. We also will maintain a database of information about our stocks with tools that ensure information is provided to the public. We will develop database tools, in conjunction with the MaizeGDB team, to help users submit requests and help us determine which seed sources to use to fulfill these requests. Each spring, we will use our database tools to determine which stocks in our core collection need to be regenerated and propagated due to supply or age of seed. In all cases, seeds are hand planted to assure purity and all pollinations are done by hand using traditional methods of maize. To propagate stocks, we use appropriate genetic controlled crossing techniques (e.g., self or sib pollinations, outcrosses; seedling, adult or pollen observations) depending on the nature of the stock (e.g., dominant vs. recessive mutants; lethal vs. homozygous viable mutants; male-sterile vs. barren stalk vs. fully fertile, etc). To prepare for harvest, we take crossing notes to prepare labels that will be attached to harvested ears. We hand-harvest the crop as individual ears to ensure the integrity of the individual stocks. The seeds are then dried on the ear. After drying, we score for kernel and ear traits, after which we shell seeds from each cob and place each ear’s seeds into individual coin-type envelopes with the ear’s pedigree and phenotype noted on the envelope. We conduct sand-bench seedling tests to determine the presence of seedling mutant traits. For adult traits, we hold seeds for observation in the next growing season. Once the quality of an ear carrying the trait of interest is assessed, the seeds from that ear are entered into our inventory database and the seeds are stored in their envelope under low humidity cold storage conditions. Samples of genetic stocks that haven’t previously been backed up into long-term storage will be sent to the NLGRP in Fort Collins, CO to ensure that all maize mutants in our collection are preserved.

Progress Report
Over the past year, the Maize Genetics Cooperation Stock Center has continued to make important progress in building and sharing genetic resources that support maize research around the world. In total, more than 3,606 seed samples were supplied in response to over 210 requests. Popular stock requests in FY2025 included the Nested Association Mapping (NAM) RILs, haploid-inducing lines, male sterile cytoplasm’s, Fast-flowering mini-maize, kernel starch quality traits, and plant architecture traits. These stocks give researchers access to tools that would be difficult or impossible to create on their own. For example, Fast-Flowering Mini-Maize lines are now helping scientists run experiments more quickly, while haploid-inducing lines make it easier to develop new inbred plants for breeding. Other lines shed light on kernel traits such as starch composition, which is important for both nutrition and industrial processing. The seed stocks resources distributed by the Stock Center accelerate discovery and allow scientists to test ideas more efficiently. In addition to distributing maize lines, the Stock Center also added a total of 29 valuable new seed stocks to our collection in FY2025 from donations by our stakeholders from across the country. These include yellow fluorescent protein marker lines donated from the University of California, Riverside, lines with chromosomal abnormalities from the University of Missouri, and a temperature-sensitive male sterile line from the University of California, Davis. Our staff also identified new mutants from our screening of a long-term mutagenesis project that were added to the collection. These additions expand the options available to scientists, who use them to explore questions about plant growth, seed quality, disease resistance, and overall crop performance. The Stock Center maintains over 3,000 mutants that show visible traits but lack genetic information. The lack of genetic information results in fewer requests for these lines. To increase their interest to our stakeholders, the Stock Center staff conducted 87 complementation tests on maize mutants with altered plant height and kernel development to add genetic specificity to these lines. This information was added to the Stock Center’s database and published for use by other scientists. The staff also developed a new low-cost sequencing method (Bulk Segregant Analysis sequencing, or BSAseq) to genetically type the mutant lines. The method used the resources of the USDA ARS high-performance computing infrastructure, SciNet. Results showed that the location of a mutated gene could be identified for approximately $200 per stock, offering an affordable way to add genetic information to these visually distinct mutants. The staff is targeting dwarf and small plant mutants for the initial expansion of the BSASeq analysis. Information obtained from this work may help in the development of a new generation of short-stature corn hybrids that are more resistant to wind damage. By making it faster and cheaper to connect visible plant traits with their underlying genes, this research speeds up the process of turning scientific discoveries into practical benefits for agricultural producers. This year, we created a new library of maize images to make it easier to see and compare different plant types in the collection. Photos were taken at four key stages of growth—from seedlings to mature ears—and linked directly to each stock’s information page residing at MaizeGDB. For many mutant lines, this is the first time pictures have ever been available, giving researchers and the public a clearer view of how these plants look. With the help of MaizeGDB staff in Ames, Iowa, we also added a bulk upload tool that streamlines adding images in the future. So far, nearly 500 images have been added and are now available online, making the collection more useful and accessible than ever before.

Accomplishments

Review Publications
Gustin II, J.L., Zimmerman, S.A., Sachs, M.M. 2025. Allelism of uncharacterized dwarf mutants in maize. microPublication Biology. https://doi.org/10.17912/micropub.biology.001504.