Intrapopulation antagonism can reduce the growth and aggressiveness of the wheat head blight pathogen Fusarium graminearum

Authors: Vaughan, Martha; Ward, Todd; McCormick, Susan; Orwig, Nathane; Hay, William; Proctor, Robert; Palmquist, Debra

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2020
Publication Date: 3/3/2020
Citation: Vaughan, M.M., Ward, T.J., McCormick, S.P., Orwig, N., Hay, W.T., Proctor, R., Palmquist, D. 2020. Intrapopulation antagonism can reduce the growth and aggressiveness of the wheat head blight pathogen Fusarium graminearum. Phytopathology. 110(4):916-926. https://doi.org/10.1094/PHYTO-09-19-0341-R.
DOI: https://doi.org/10.1094/PHYTO-09-19-0341-R

Interpretive Summary: The fungal plant pathogen Fusarium graminearum causes Fusarium head blight (FHB), a devastating disease of cereal crops that reduces yield and contaminates grain with mycotoxins, such as the trichothecene toxin deoxynivalenol, that pose health risks to humans and livestock. Co-infection of individual wheat heads by multiple FHB isolates is common in the field and competitive interactions among different FHB species or populations can reduce FHB and mycotoxin accumulation in wheat. To further understand the implications of interactions among FHB pathogens we compared the growth, aggressiveness toward wheat, and trichothecene accumulation of individual isolates in relation to mixtures of isolates that come from the same population and share the same trichothecene toxin type. We discovered that competitive interactions between isolates from the same population and toxin type reduce fungal growth in culture and disease severity in wheat. These competitive interactions were observed within both of the major F. graminearum populations found in North America. However, we documented a greater level of competition, resulting in larger reduction in FHB score, among isolates from the native NA1 population as compared to the recently introduced NA2 population, indicating that competitive interactions may be greater in fields where NA1 isolates predominate. These findings highlight the potential to use knowledge of regional FHB population diversity to improve forecasting and management of FHB and mycotoxin contamination in grain.

Technical Abstract: Fusarium graminearum is a causal agent of Fusarium head blight (FHB), a disease that reduces yield and quality of cereal crops and contaminates grain with mycotoxins that pose health risks to humans and livestock. Interpopulation antagonistic interactions between isolates that produce different trichothecene mycotoxins can reduce FHB in wheat, but it is not known if interactions between isolates with a shared population identity and produce the same trichothecenes have a similar effect. Using isolates from the predominant F. graminearum populations in North America (NA1 and NA2), we examined intrapopulation interactions by comparing growth, disease progression, and toxin production of individual isolates to multi-isolate mixes. In vitro, mycelial growth was significantly greater for most NA1 and NA2 isolates when cultured individually than when cultured as a mixture of isolates from the same population. In susceptible wheat Norm, FHB generally progressed faster in heads inoculated with an individual isolate versus a multi-isolate mixture, but the antagonistic effect of intrapopulation interactions was more pronounced for NA1 than NA2 isolates. By contrast in moderately resistant wheat Alsen, mixtures of isolates from either population caused obvious reductions in FHB development. Mycotoxin contamination was not consistently affected by intrapopulation interactions and varied depending on the interacting isolates from either population. Our results indicate that pathogen population dynamics may influence FHB, and therefore understanding regional pathogen composition could improve disease forecasting and local management practices.