Genome-wide association study of fungicide sensitivity in a Fusarium graminearum population collected from North Dakota

Authors: POUDEL, BIKASH - North Dakota State University; MULLINS, JOSEPH - North Dakota State University; Fiedler, Jason; Chao, Shiaoman; ZHONG, SHAOBIN - North Dakota State University

Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2023
Publication Date: 4/22/2024
Citation: Poudel, B., Mullins, J., Fiedler, J.D., Chao, S., Zhong, S. 2024. Genome-wide association study of fungicide sensitivity in a Fusarium graminearum population collected from North Dakota. Journal of Phytopathology. https://doi.org/10.1094/PHYTO-05-23-0180-KC.
DOI: https://doi.org/10.1094/PHYTO-05-23-0180-KC

Interpretive Summary: Fusarium head blight (FHB) is a destructive disease of small grains that decreases yield and ruins grain quality. FHB is caused by a naturally occurring fungal pathogen and a common method to limit the disease is the timely application of fungicides during flowering. Different strains of the FHB pathogen have been collected in North Dakota fields over the last four decades to monitor the population and ensure relevant disease screening for breeding efforts. In this study, we evaluated the historical fungal population for resistance to two commonly used fungicides. We found that most of the strains were still sensitive at regular concentrations, but a few displayed some moderate resistance. Additionally, with analysis of the genome, we identified seven fungal genes that could be playing a role in this increased resistance. This information is important because it informs the producers that fungicide-resistance pathogens are present in the environment, and it helps researchers understand the basic biology of resistance to develop more effective methods of control.

Technical Abstract: Fusarium head blight (FHB) is a destructive disease of small grains. The disease is predominantly caused by a haploid ascomycete fungus Fusarium graminearum in North America. To understand the genetics of quantitative traits in this fungal pathogen, we conducted a genome-wide association study (GWAS) of fungicide sensitivity to two demethylation inhibition (DMI) class fungicides, tebuconazole and prothioconazole, using a temporal F. graminearum population of 183 isolates collected between 1981 and 2013 from North Dakota.Baseline sensitivity to tebuconazole and prothioconazole was established using 21 isolates that were collected between 1981 and 1995. Most fungal isolates were sensitive to both tebuconazole and prothioconazole, however, five isolates showed significantly reduced sensitivity to prothioconazole. A GWA study identified one significant marker-trait association (MTA) on chromosome 3 for tebuconazole resistance while six significant MTAs, one on chromosome 1, three on chromosome 2, and two on chromosome 4 were detected for prothioconazole resistance. Functional annotation of the MTAs for tebuconazole revealed a basic helix loop helix (bHLH) domain containing protein that reinforces sterol in the fungal membrane as a candidate gene.. On the other hand, prothioconazole resistance involved mechanisms including RNAi, detoxification by ubiquitin-proteasome pathway, and reinforcing membrane integrity. Considering these concerted efforts from the pathogen towards overcoming chemical control, continued monitoring of fungal sensitivities to commercially applied fungicides, especially those containing prothioconazole, is warranted to eliminate risks of fungicide resistance.