Poster # 404

Ogheneyoma Ikpeni ¹, Simran Goyal ^{1, 2}, Mark Farman ¹, Robert Proctor ³, Niki McMaster ⁴, David Schmale ⁴, Carl Bradley ¹, David Van Sanford ⁵, Lisa Vaillancourt ¹
1. University of Kentucky, Department of Plant Pathology, Lexington, KY
2. Current Address: University of Maryland, Department of Plant Science and Landscape Architecture, College Park, MD
3. National Center for Agricultural Utilization Research (NCAUR), USDA-ARS, Peoria, IL
4. Virginia Tech, School of Plant Environmental Sci, Blacksburg VA
5. University of Kentucky, Department of Plant and Soil Sciences, Lexington KY
Corresponding Author: Lisa Vaillancourt, vaillan@uky.edu

Ikpeni, Ogheneyoma

Ogheneyoma.Ikpeni@uky.edu

Variation in trichothecene chemotype among Fusarium graminearum populations has been linked to shifts in the incidence and severity of Fusarium Head Blight (FHB) epidemics across North America. The NA2 population, which is usually associated with the 3ADON chemotype and higher toxin levels than the predominant 15ADON-producing NA1 population, has been expanding its range. However, it is unclear whether the 3ADON chemotype has contributed directly to this expansion. To test the hypothesis that the 3ADON chemotype increases pathogen competitiveness during infection of wheat heads, we conducted co-inoculation experiments with segregating progeny from a cross between a 15ADON MAT-deletion heterothallic tester strain and a 3ADON wild-type homothallic isolate. Seven progeny pools were constructed, each comprising five 3ADON and five 15ADON strains selected randomly. Pools were inoculated onto spikes of the susceptible spring wheat line Wheaton with or without fungicide. Disease severity was assessed at 7-, 10-, and 14-days post-inoculation and summarized as area under the disease progress curve (AUDPC). Mycotoxin quantities and profiles were measured in wheat heads, and the trichothecene genotypes of recovered progeny were determined by using TRI gene-based multiplex PCR assays. In all three trials, the progeny pools produced less disease and accumulated less mycotoxin than the parental strains in the absence of fungicide, possibly due to antagonistic interactions. Fungicide treatment reduced overall disease and mycotoxin levels, although the 3ADON parent was less sensitive to the fungicide than the 15ADON parent. Analysis of the mycotoxin profiles showed that there was no significant bias in favor of 3ADON versus 15ADON in the wheat heads inoculated with any of the pools, in either the presence or the absence of fungicide. Analysis of 24 single-spored strains per pool that were recovered from the wheat heads also mostly showed no significant deviation from a 1:1 ratio of 3ADON to 15ADON trichothecene genotypes across all pools, regardless of fungicide treatment. Individual pools did exhibit dominance by certain clones, but this was not associated with the trichothecene genotype. These results indicate that the 3ADON chemotype alone does not confer a competitive advantage in mixed infections, and that the recent expansion of 3ADON populations in North America is likely driven by other factors. The recovery of dominant fungal clones from mixed infections supports the hypothesis that some of these competitiveness factors are genetic. These genetic factors will be explored in future studies to understand their function and identify associated markers to track them in the population.

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