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

2022 Annual Report

Accomplishments
1. Discovered Fusarium head blight resistant wheat becomes less nutritious at elevated carbon dioxide. Higher atmospheric carbon dioxide can cause some cereal crops to produce more starch resulting in a lower grain protein and mineral content, making it less nutritious. In addition, these crops may become more susceptible to disease. Fusarium head blight is a fungal disease of wheat, barley, and other cereal crops that causes billions of dollars in annual yield losses and contamination with mycotoxins which makes the grain unsafe to eat. ARS researchers in Peoria, Illinois, in collaboration with wheat breeders from the University of Minnesota, compared wheat varieties that were susceptible or moderately resistant to the disease and measured the nutritional quality of the grain from plants grown with current or elevated concentrations of carbon dioxide. They discovered that wheat varieties with moderate resistance to Fusarium Head blight were more likely to produce grain with poorer nutritional quality when they were grown at elevated carbon dioxide. Furthermore, some F. graminearum strains responded to the reduced nutritional content in moderately resistant wheat by producing more mycotoxins. This study demonstrated the importance of identifying wheat cultivars that maintain nutritional quality and disease resistance with rising atmospheric carbon dioxide.

2. Demonstrated atmospheric carbon dioxide, temperature and Fusarium strain differentially influence mycotoxin contamination of corn and wheat. Fusarium fungi are devastating pathogens that infect cereal crops causing billions of dollars in annual yield losses and poison grains with mycotoxins making it unsafe to eat. Climate change is predicted to increase the frequency and severity of Fusarium disease and mycotoxin contamination of cereal grains. However, it has been unclear how rising atmospheric carbon dioxide and temperature will specifically impact Fusarium graminearum ear rot of corn and head blight of wheat. ARS researchers in Peoria, Illinois, showed that both economically important crops were more susceptible to mycotoxin contamination when grown at elevated carbon dioxide, but warmer temperatures reduced mycotoxin contamination. Additionally, the effects of carbon dioxide and temperature were dependent on the F. graminearum strain, and under the combined stress conditions a strain that produced the highest amount of mycotoxin in corn, produced the least in wheat. This study provides valuable information needed to determine the risk of Fusarium disease outbreaks and mycotoxin contamination in the future and will be of interest to farmers and regulatory agencies.

3. Revealed that genetic analyses reveal that gene organization can distinguish friend from foe fungi. Trichothecene mycotoxins are poisonous compounds produced by the fungus Fusarium and ten other kinds of fungi. These mycotoxins help Fusarium cause infection of crop plants such as wheat and potatoes. In Fusarium, and most of the other fungi that produce trichothecenes, the eight to fifteen genes that control their production are grouped together. However, gene number and organization vary in Trichoderma species, which can be beneficial fungi that protect crops or harmful fungal pathogens. ARS researchers in Peoria, Illinois, in collaboration with researchers in Leon, Spain, analyzed 35 Trichoderma species to see if they produced trichothecenes and to determine how their toxin genes were organized. They found that the tri5 gene, which controls the critical first step in trichothecene production, is widely distributed in Trichoderma, but other toxin genes and trichothecene production are less common. Trichoderma species that have only tri5 were able to inhibit trichothecene production by other fungi. These results indicate that Trichoderma species with only tri5 have the potential to control crop diseases caused by trichothecene producing species of Fusarium and reduce contamination of crops with the toxins

4. Determined controlling pathogen load on neighboring plants may be key to reducing mycotoxin contamination. The plant microbiome, including pathogens and beneficial microbes, can have direct impacts on plant health and productivity, but where precisely plants get their microbiomes remains unclear. Using next generation sequencing of fungal communities, ARS researchers in Peoria, Illinois, in collaboration with North Carolina State University and Indiana University researchers, discovered that soil fungi only marginally contributed to the fungal communities on plant leaves. Other surrounding plants were the primary source of fungi to the leaf microbiome, and the extent to which other plants contributed to leaf fungal microbiomes was dependent on precipitation with more rain leading to more plant-to-plant fungal spread. This knowledge can be applied to understanding how pathogens or biocontrol microorganism spread within natural and agricultural communities.

5. Updated Fusarium species identification database. Fusarium is a devastating group of diverse toxin-producing plant pathogens responsible for multibillion U.S. dollar losses each year to the world’s agricultural economy. Accurate species-level identification of these pathogens is crucial for disease diagnosis and management. However, the Fusarium genus is comprised of more than 400 genetically distinct species that cannot be accurately identified by morphology alone. To address the critical need for species identification, ARS researchers in Peoria, Illinois, in collaboration with researchers at Pennsylvania State University, improved identification of Fusarium pathogens by updating FUSARIUM-ID (https://github.com/fusariumid/fusariumid), a web-accessible DNA sequence database for the identification of Fusarium, by adding new DNA sequence data that help distinguish between species. This more comprehensive database will enable scientists worldwide to accurately identify Fusarium species using DNA sequence data. This database is being used by a wide range of scientists and quarantine officials charged with minimizing the threat these pathogens pose to global agricultural biosecurity and food safety.

6. Discovered tissue-specific wheat defense responses correlate with susceptibility to Fusarium infection. The fungus Fusarium graminearum causes Fusarium head blight (FHB), a devastating disease of wheat. FHB not only reduces crop yield but also contaminates grain with a fungal toxin called vomitoxin, that make the grain unsafe to eat. One way that plants react to fungal infection is by releasing reactive oxygen species (ROS). ARS researchers in Peoria, Illinois, evaluated ROS responses in different parts of the wheat plant that had been treated with chitin, a polysaccharide that is a major component of fungal cell walls, insect exoskeletons, and crustacean shells. While there was no ROS increase in wheat leaves treated with chitin, typical ROS responses were found in the central part of the wheat heads, the route by which FHB spreads. The discovery that the chitin induced ROS response is correlated with tissue susceptibility suggests that the ROS response may assist F. graminearum infection, and comparisons between tissue responses may aid in identifying methods of resistance. Further, this study identified defense genes that were turned on in wheat heads treated with chitin. These genes may serve as novel targets to improve disease resistance.

U.S. DEPARTMENT OF AGRICULTURE

Mycotoxin Prevention and Applied Microbiology Research: Peoria, IL