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In maize, abundant pollen production and easy controlled pollination permit the direct mutagenesis of pollen to produce populations of independent mutant lines. Pollen can be treated with alkylating agents, such as ethyl methanesulfonate (EMS), to induce point mutations. The ease of applying and decontaminating this mutagen after the mutagenesis application and the advantages provided by the mutation spectra for subsequent bioinformatic analysis make EMS an attractive mutagen. We provide a maize pollen mutagenesis protocol with a list of critical supplies, a step-by-step procedure, and troubleshooting tips. Pollen is freshly collected and suspended in an emulsion of EMS and paraffin oil. The slurry of pollen, oil, and EMS is then directly placed on prepared maize silks to perform pollinations. Mutations result during embryogenesis due to replication-dependent mispairing at alkylated residues contributed by sperm nuclei. Thus, each seed bears an independent set of mutations. These progenies can be analyzed directly, as is the case in targeted mutagenesis experiments or the exploration of dominant genetic variation. Alternatively, the progenies of self-pollinated plants can be screened in the next generation to discover novel recessive mutations. In addition to the dose of EMS and contact time, the genetic background of maize can significantly influence outcomes, and some optimization of dose and contact time may be required for a genetic background and specific use case. Although we outline good practices for safe handling of EMS and waste, researchers should consult their local safety officers to ensure safe handling, decontamination, and disposal of EMS, which is toxic.
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This content will become publicly available on April 1, 2027
Ethyl Methanesulfonate Treatment of Maize Seed for Recovery of Vegetative Mutant Sectors and Segregating Germinal Mutations
Seed mutagenesis using alkylating chemical agents such as ethyl methanesulfonate (EMS) can generate somatic and germinal mutations in many plant species. In monoecious plants like maize, the sperm- and egg-producing reproductive germlines are derived from distinct cell lineages in the embryo. This separation results in independent mutations inherited via the egg and sperm lineages and prevents the recovery of recessive mutant phenotypes in diploid progeny after the first round of self-pollination. Thus, two generations of self-pollination are required to screen for recessive mutations when conducting seed mutagenesis. The additional time and manual self-pollination make this approach laborious. However, a high mutation rate and the ability to screen for somatic sectors in heterozygous mutant plants and other defined genetic backgrounds make seed mutagenesis an effective but underutilized mutagenesis tool for maize research. This protocol provides the directions and optimization steps to perform effective seed mutagenesis in maize. A high frequency of somatic mutations from seed mutagenesis can be achieved, but comes at the expense of poor and disordered growth, failure to form reproductive structures, and low or no seed production at high EMS concentrations or long contact times. In experiments where germinal mutations are a goal, an optimum dose of EMS is required in the first generation. Maize genetic backgrounds vary in their sensitivity to EMS, requiring some pilot testing in new genetic backgrounds. Researchers using this protocol can carry out seed mutagenesis safely and effectively to develop libraries of mutants or alleles for various experiments.
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- Award ID(s):
- 2309932
- PAR ID:
- 10687260
- Publisher / Repository:
- Cold Spring Harbor Press
- Date Published:
- Journal Name:
- Cold Spring Harbor Protocols
- Volume:
- 2026
- Issue:
- 4
- ISSN:
- 1940-3402
- Page Range / eLocation ID:
- pdb.prot108650
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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