Project : USDA ARS

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Research Project: Improving Food Safety by Controlling Mycotoxin Contamination and Enhancing Climate Resilience of Wheat and Barley

Location: Mycotoxin Prevention and Applied Microbiology Research

2025 Annual Report

Objectives
Objective 1: Identify Fusarium graminearum (Fg) virulence factors and/or fitness traits that can be targeted to reduce grain mycotoxin contamination. [C1, PS2] Sub-objective 1.A: Identify and characterize core effectors of Fg that can be targeted to reduce initial infection of wheat and barley. Sub-objective 1.B: Identify and characterize Fg population-specific factors that contribute to differences in virulence and mycotoxin contamination of wheat and barley. Objective 2: Identify germplasm that can be used by breeders to simultaneously target climate resilient mycotoxin resistance and high grain quality traits. [C1, PS2] Sub-objective 2.A: Evaluate the resilience of FHB resistance to e[CO2] in MR and S wheat cultivars. Sub-objective 2.B: Determine the impact of e[CO2] on the production of Fg mycotoxins and other secondary metabolites during growth on wheat and barley grains. Sub-objective 2.C: Determine the impact of e[CO2] on the nutritional quality of FHB MR parent wheat lines and identify potential breeding strategies to maintain grain quality. Objective 3: Manipulate microbial populations or metabolites to control trichothecene contamination of grain and malting barley. [C1, PS2, PS5] Sub-objective 3.A: Evaluate the efficacy of Sarocladium and Paenibacillus as biocontrol agents to control FHB and mycotoxin contamination of grains. Sub-objective 3.B: Determine how perithecial pigmentation affects production, discharge, and germination of Fusarium ascospores so that these metabolites can be manipulated to reduce Fg inoculum in the field. Sub-objective 3.C: Develop a biofumigant from plant derived metabolites to inhibit fungal growth and mycotoxin production during barley malting.

Approach
Mycotoxins are poisonous fungal metabolites that contaminate cereals, making them unsafe for human or livestock consumption. Contamination originates in the field during grain development when crops become infected by mycotoxigenic fungal pathogens that can result in diseases with significant economic losses. Fusarium head blight (FHB), is a devastating disease of wheat and barley that is caused primarily by the fungal pathogen Fusarium graminearum (Fg) which produces mycotoxins, including trichothecenes and zearalenone. FHB is a complex ecological problem that has been difficult to eradicate because infection is dependent on multiple interacting factors. The severity of FHB is contingent on the prevalence, virulence, and aggressiveness of the pathogen, the genetic potential of the host plant’s resistance, as well as other abiotic and biotic environmental factors that influence the outcome of the plant-pathogen interactions. Previous efforts by scientists in the FHB community have laid a foundation of information on pathogen virulence and host resistance, but we need to further understand how environmental factors shape the outcome and impact of interactions. Using a holistic approach that tackles the problem from multiple angles, we propose to target factors that can be manipulated to impose mycotoxin control: 1) Fg pathogenic fitness, 2) resilience of crop resistance, and 3) beneficial microorganisms and microbial or plant metabolites. Knowledge obtained from this approach will aid in the development of integrated climate-resilient control strategies for FHB and mycotoxin contamination of grains, thereby reducing the impact of mycotoxins on our food supply. These studies will ultimately benefit growers; small grain breeders; stakeholders in the food and feed industry; other research scientists; regulatory agencies (United States Food and Drug Administration, USDA Federal Grain Inspection Service, and Animal Plant Health Inspection Service); and most importantly the consumer.

Progress Report
Objective 1: Mycotoxins are harmful substances produced by fungi that infect and contaminate crops. Fusarium graminearum is a fungus that causes a serious disease in wheat and barley called Fusarium Head Blight (FHB). This disease not only damages crops but also produces harmful toxins called mycotoxins, including vomitoxin which is notoriously known for inducing vomiting and feed refusal. Because of FHB and mycotoxin contamination, farmers in the U.S. lose billions of dollars each year due to lower crop yields and unsafe grain. ARS scientists in Peoria, Illinois are working to stop this fungus by targeting the proteins and toxins it uses to infect plants. This year, scientists found a new protein that plays a critical role in how the fungus attacks wheat and barley. They tested different combinations of genetic changes to block both this effector and a key toxin-making gene called TRI5. The results showed that stopping both can help plants resist the disease better. Within the Fusarium graminearum species, different populations behave differently. One emerging population in North America, called NA3, is especially good at infecting wheat because it makes a unique toxin called NX. When scientists tried to block other NA3-specific proteins, it didn’t control the disease. These results emphasize the critical role of NX in initiating wheat infection and the potential ability to stop the emerging NA3 population from initiating disease in U.S. wheat by blocking NX production. Objective 2: FHB and mycotoxin outbreaks are strongly associated with adverse weather conditions that weaken the crops and make them more susceptible. To help American farmers grow wheat that can stay strong and resistant to FHB and mycotoxins even during stressful conditions, ARS scientists in Peoria, Illinois studied different types of wheat to see how well they could fight off disease. They looked at wheat with two specific regions of DNA that are linked to FHB resistance, Fhb1 and Fhb5. These regions worked well when the weather was favorable, but under stress, the plants didn’t defend themselves as well. Scientists are now trying to figure out which plant chemicals change during stress and make the wheat more vulnerable. Another resistance gene, Fhb7, showed impressive results. Even when disease pressure was strong, wheat with Fhb7 had 97% less of the harmful toxin, vomitoxin. So far, Fhb7 is the best option for keeping wheat safe even under stressful environments. ARS scientists also compared F. graminearum mycotoxin production levels under variable conditions and on different wheat and barley cultivars. Analyses identified which primary metabolites in the different crops and cultivars were associated with the highest levels of mycotoxin. This knowledge is important for breeders to understand how grain quality traits influence susceptibility under variable conditions. Changes to primary metabolism due to the stress of elevated atmospheric carbon dioxide (CO2), which makes the plants produce more sugar but less protein, lowers the grain’s nutritional value. Wheat with high FHB resistance lost a lot more protein under high CO2 than FHB susceptible wheat. ARS scientists tried adding extra nitrogen to fix this, but it didn’t help much. Now they are searching for better ways to protect both crop health and food quality. Objective 3: ARS scientists in Peoria, Illinois are finding ways to help American farmers protect their cereal crops from harmful fungi by investigating ways to use beneficial microbes that can naturally defend plants against pathogens. Fusarium fungi cause serious issues in crops like corn and wheat by producing harmful mycotoxins, such as trichothecenes and fumonisins. Mycotoxin contaminated grain has reduced quality, utility and value and cause serious food safety concerns. ARS scientists discovered that a beneficial fungus called Sarocladium zeae protects crops from Fusarium. Initial field experiments involved injecting S. zeae into corn, but this method wasn’t practical for large-scale farming. Scientists developed a spraying method to apply S. zeae onto corn plants. This method proved effective, showing that the beneficial fungus could spread to the corn kernels and protect them at a farm scale. This approach might also be useful for protecting barley using a similar fungus, S. strictum. Understanding the mechanism by which S. zeae protects the crops is essential to maintain its effectiveness under field conditions. It was found that S. zeae produces two chemical compounds, Massoia lactone and cadinol, which help inhibit the production of mycotoxins by Fusarium fungi. Studies showed that when S. zeae is grown with Fusarium, it increases the production of these helpful compounds and reduces mycotoxin production by Fusarium. Through these evaluations, scientists identified specific genes in S. zeae responsible for making cadinol and used engineered yeast to produce large amounts of it for testing in crop protection products. This research brings American farmers closer to using natural, biological methods to protect their crops from harmful fungi like Fusarium. By understanding how beneficial microbes work and developing practical ways to use them, farmers can reduce reliance on chemical pesticides, leading to safer and more sustainable agriculture. Emerging mycotoxin threats remain a significant concern of American farmers, therefore monitoring farms for Fusarium species and mycotoxin risk is essential to provide farmers with adequate time to respond. Therefore, ARS scientists sampled wheat and barley farms across several states to identify which Fusarium species are present and the mycotoxins they produce. High levels of a toxin called nivalenol were found in Illinois crops, indicating the need for ongoing monitoring and targeted control strategies. In North Dakota, multiple Fusarium species were identified, increasing the complexity of managing different mycotoxin risks. ARS scientists in Peoria, Illinois are also testing practical ways to prevent disease spread. Fusarium spores spread through structures known as perithecia, which are darkly pigmented. Scientists found that spores from nonpigmented perithecia caused less disease and were more sensitive to UV light, leading to fewer spores spreading and less crop contamination. Therefore, reducing the ability of the fungus to produce these pigments represents an innovative method to reduce the fungus success at spreading and causing disease in crops. Mycotoxin contamination during barley malting cost American brewing industries hundreds of millions of dollars yearly. To control mycotoxins during barley malting, scientists optimized biofumigation using mustard seed meal. Brown mustard seed meal proved highly effective, and adding White mustard seed meal also showed strong antimicrobial activity without affecting the quality of the malt.

Accomplishments
1. Novel target to reduce Fusarium head blight of wheat and barley. The fungus Fusarium graminearum causes Fusarium head blight, a serious disease in wheat, barley and other cereals. Fusarium head blight significantly reduces crop yield and contaminates grain with vomitoxin, threatening food safety and security. To develop effective methods to control Fusarium head blight, we need to understand how the fungus causes disease. ARS scientists in Peoria, Illinois, discovered a Fusarium enzyme called FgRGAE that degrades plant cell walls in the early stages of wheat and barley infection. When FgRGAE’s enzymatic function was disrupted, it compromised the ability of the fungus to cause infection. This study improves our understanding of how Fusarium successfully invades the plant cell walls to cause disease and identifies an ideal target to control Fusarium head blight and reduce vomitoxin contamination in the food and feed supply.

2. Vomitoxin transporter to improve food safety. Fusarium head blight (FHB) costs U.S. wheat and barley farmers billions of dollars in annual losses. The fungal pathogen Fusarium graminearum, which causes FHB, not only devastates crop yields but also contaminates grain with poisonous trichothecene toxins, such as vomitoxin. If consumed, these toxins can cause serious health problems for humans and livestock. Due to the lack of resistant cereal crop varieties and emergence of fungicide-resistant fungal strains, it is critical to develop novel methods to control FHB and vomitoxin contamination. Plant transporters are proteins that can eliminate toxins by transporting them out of plant cells where they can cause harm to the plant or the potential crop consumers. ARS researchers in Peoria, Illinois, identified a transporter (AtDTX1) from the model plant Arabidopsis that can successfully pump trichothecenes out of plant cells. This transporter along with others has the potential to reduce trichothecene contamination and improve food safety.

3. Alerted wheat and barley producers of a food safety threat. The fungus Fusarium graminearum is a serious threat to food safety because it causes a disease called Fusarium head blight in wheat and barley, and it also contaminates the grain with harmful toxins. In the United States, most strains of this fungus come from two main populations, which usually produce a toxin known as vomitoxin (VOM). However, scientists have recently found a third population appearing in North America. This third population produces a different toxin called NX, which has slightly different chemical makeup than VOM. ARS scientists in Peoria, Illinois, discovered that this third population produces and accumulates more toxin in wheat and barley than the common VOM-producing populations. Even more concerning, NX contaminated grain doesn't always show corresponding signs of visible disease, and current testing methods, designed to detect VOM, do not detect NX. This research is important because it warns wheat and barley farmers, food processors, and consumers about a potential overlooked toxin in cereal crops and products.

4. Informed Illinois wheat farmers of fungi causing crown rot. Fusarium crown rot (FCR) is a global disease of wheat and other cereal crops. FCR outbreaks have caused as much as 35% yield losses, devastating U.S. wheat production. In Illinois, winter wheat is the third largest crop produced, with approximately 700,000 acres harvested annually. ARS researchers in Peoria, Illinois and Raleigh, North Carolina, in collaboration with scientists from Canada, detected high incidence of FCR in four of fifteen Illinois wheat fields surveyed in 2022. To inform Illinois wheat farmers of the type of fungal pathogens causing FCR, wheat crowns and heads were sampled, and genetic sequencing was used to identify the fungal species. Three Fusarium species were identified as the most common fungi causing FCR in Illinois, including the mycotoxin producing pathogen Fusarium graminearum, which typically causes Fusarium head blight in wheat. Identifying the pathogen responsible for crown rot is crucial, as it enables targeted treatments, improves crop quality and yield and boosts overall farm profitability.

5. Natural biofumigation method to mitigate mycotoxins during malting. Mycotoxin contamination during barley malting results in millions of dollars in annual losses for the malting and brewing industry. The high moisture and cool temperatures that promote seed germination during the malting process are also ideal for fungal growth and mycotoxin production, causing food safety concerns and undesirable product traits like beer gushing. ARS researchers developed a biofumigation treatment that uses natural plant-derived compounds to prevent fungal growth and mycotoxin accumulation during malting. No adverse effects on malt quality and no residual biofumigants were detected on the final product. This biofumigation method represents a safe, cost effective, practical approach to control mycotoxins during malting and will significantly benefit the $62 billion U.S. brewing industry.

6. Molecular diagnostic tool to determine Fusarium toxin type. The fungus Fusarium graminearum is a devastating fungal pathogen that causes disease in corn, wheat and barley, and contaminates grain with harmful toxins. Because contaminated grain must be diverted from the food supply, fungal toxins cost U.S. farmers and industries billions annually. To accurately detect the different toxins and target control strategies, it is essential for grain producers, extension specialists and pathologists to be able to accurately determine which type of toxin a fungal strain produces. To support pathogen and toxin surveillance efforts, ARS scientists in Peoria, Illinois, and St. Paul, Minnesota, developed a rapid and robust molecular diagnostic assay that can be used to differentiate Fusarium strains by the different toxins they produce. This diagnostic tool provided producers, extension specialists and regulatory agencies with rapid methods to detect and therefore mitigate emerging mycotoxin threats to public health.

7. Identification of the enzymes that speed up fungal toxin production could also help slow it down. Fungi make many different chemicals, including harmful ones called mycotoxins. One important group of mycotoxins is called trichothecenes. These are especially dangerous for food and animal feed because they are very toxic and often found in crops. All trichothecenes have the same basic chemical structure, which is important for how harmful they are. For a long time, scientists thought this structure formed through a slow natural reaction, but that didn’t explain how quickly fungi make these toxins. ARS scientists in Peoria, Illinois, in collaboration with university researchers in Santa Barbara, California, used both genetic and chemical methods to solve this mystery. They discovered a new process that uses two enzymes to quickly build the basic structure of trichothecenes. This explains how fungi are able to produce these toxins so fast. Their discovery could help scientists find new ways to stop these harmful chemicals from getting into crops and increase profit for corn, wheat and barley farmers and livestock producers.

8. Antibodies to detect new NX- toxins. The fungus Fusarium graminearum is a devastating pathogen that causes disease in corn, wheat and barley, and contaminates grain with harmful toxins. Recently, a new group of toxins called NX-toxins were found in U.S. cereals. NX-toxins are similar to the better-known "vomitoxin." There are currently no rapid screening tests for NX-toxins. ARS scientists in Peoria, Illinois, developed several antibody-based screening assays for the NX-toxins in wheat. These are the first rapid screening tests for this group of toxins and will be important tools to remove infested commodities from the human food and animal feed supply chains.

U.S. DEPARTMENT OF AGRICULTURE

Mycotoxin Prevention and Applied Microbiology Research: Peoria, IL