The emerging Fusarium graminearum NA3 population produces high levels of mycotoxins in wheat and barley

Authors: RHOADES, NICHOLAS - Orise Fellow; McCormick, Susan; Vaughan, Martha; Hao, Guixia

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2024
Publication Date: 9/20/2024
Citation: Rhoades, N.A., McCormick, S.P., Vaughan, M.M., Hao, G. 2024. The emerging Fusarium graminearum NA3 population produces high levels of mycotoxins in wheat and barley. Toxins. https://doi.org/10.3390/toxins16090408.
DOI: https://doi.org/10.3390/toxins16090408

Interpretive Summary: An emerging Fusarium population produces relatively higher toxin in wheat and barley. The fungal pathogen Fusarium graminearum poses significant food safety concerns because it not only causes Fusarium head blight (FHB) on wheat and barley but also contaminates grains with harmful mycotoxins. Most F. graminearum strains in the U.S. produce vomitoxin deoxynivalenol (DON), but an emerging North American strain of F. graminearum population NA3 produces the mycotoxin called NX with a slightly different chemical structure. Less information is known about the NA3 population compared to North American populations of NA1 and NA2. ARS researchers in Peoria, Illinois, compared FHB and toxin levels in wheat and barley infected with the NA3 population to NA1 and NA2 populations. They found that NA3 population caused a similar level of disease in wheat with NA1 and NA2 populations during initial infection, but it produced and accumulated more mycotoxins in comparison to the other two populations. Although NA3 caused less disease in barley compared to NA1 population, NA3 population produce relatively higher toxin than NA1 population. Like DON, NX toxin was not associated with the disease development in barely. This study provides insights into the potential threat of the emerging NA3 population and associated mycotoxin.

Technical Abstract: Fusarium graminearum (Fg) is the primary causal agent of Fusarium head blight (FHB) on wheat, barley, and other small grains in North American fields. FHB results in yield reduction and contaminates grain with mycotoxins that pose threats to human and livestock health. Three genetically distinct North American (NA) populations of Fg have been characterized, which differ in their predominant trichothecene chemotype: NA1/15-acetyl-deoxynivalenol (15-ADON), NA2/3-acetyl-deoxynivalenol (3-ADON), and NA3/3a-acetoxy, 7,15-dihydroxy-12,13-epoxytrichothec-9-ene (NX-2). Recent studies found that the NA3 population had significantly less spread on point-inoculated wheat spikes than the NA1 and NA2 populations, and NX toxins are important for Fg spread and initial infection in wheat. In this study, to compare the effect of the three populations on initial infection and mycotoxin production on different hosts, we dip-inoculated spikes of moderately resistant wheat cultivar Alsen and barley cultivar Voyager using five strains from each population and evaluated disease, mycotoxin accumulation, and mycotoxin production per unit fungal biomass. In dip-inoculated wheat spikes, the NA3 population consistently produced significantly more toxin per fungal biomass and accumulated more mycotoxin per plant biomass than the NA1 and NA2 regardless of disease levels caused by the three populations. In contrast to its critical role during wheat infection, NX toxins had no effect on barley infection. In dip-inoculated barley, the NA1 population was more infectious and caused more FHB symptoms than the NA2 and NA3 populations, however, NA3 population produced significantly higher toxin per fungal biomass in infected barley tissues than the NA1 population did. This study provides critical information on the newly emerging NA3 population, which produces high amounts of NX toxin and poses a potential food safety concern.