The 2022 Fusarium head blight outbreak in Ethiopia: Emerging pathogens, mixed mycotoxins, and interspecies interactions

Authors: DEGENRING, LIZA - University Of Minnesota; GEMECHU, ASHENAFI - Ethiopian Institute Of Agricultural Research; RAFIEEBANADAKI, VAHIDEHALSADAT - Swedish University Of Agricultural Sciences; Broz, Karen; REGASA, GIZACHEW - Ethiopian Institute Of Agricultural Research; MUNSAMY, KIARA - University Of Pretoria; YILMAZ, NERIMAN - University Of Pretoria; DONG, YANHONG - University Of Minnesota; Rouse, Matthew; Drott, Milton

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2025
Publication Date: 7/10/2025
Citation: Degenring, L., Gemechu, A., Rafieebanadaki, V., Broz, K.L., Regasa, G.H., Munsamy, K., Yilmaz, N., Dong, Y., Rouse, M.N., Drott, M.T. 2025. The 2022 Fusarium head blight outbreak in Ethiopia: Emerging pathogens, mixed mycotoxins, and interspecies interactions. Plant Disease. https://doi.org/10.1094/PDIS-01-25-0126-RE.
DOI: https://doi.org/10.1094/PDIS-01-25-0126-RE

Interpretive Summary: Fusarium head blight (FHB) is a devastating disease of wheat that causes billion-dollar losses every year and is associated with toxic contamination of grains. This disease poses a serious threat to human and animal health as well as food safety and security. This problem has grown worse in recent years and is occurring in new areas. Indeed, in 2022, FHB reached epidemic proportions in Ethiopia, a country where this disease has not historically been a problem. We investigated the cause for the emergence of this pathogen in this region. We discovered that many of the wheat samples from Ethiopia in 2022 are contaminated with dangerous levels of fungal toxins. The pathogens causing the disease in Ethiopia, include common species found in the United States and Europe, but also include species that have not been described elsewhere. Indeed, we discovered a new FHB-causing species that we formally describe as Fusarium kistlerii. We also show that the 2022 outbreak was associated with inter-species interactions that may have contributed to disease severity. Overall our results emphasize that FHB-causing species that are rare in other parts of the world have emerged in Ethiopia. We suggest that in a globalized agricultural economy, that studying these emerging species can help inform our understanding of FHB and safeguard against species that could emerge in other parts of the world as well.

Technical Abstract: As Ethiopia pushes towards self-sufficiency in wheat production, it has escaped the devastating effects of fusarium head blight (FHB), a disease that threatens wheat production globally. In 2022, FHB incidences in Ethiopia rose to 80%, with some areas experiencing 100% disease severity. Here we provide insights into the etiology of this disease outbreak and point toward future directions to mitigate the emerging threat of FHB on a global scale. While most wheat samples from 2022 exhibited low trichothecene levels, 26% exceeded recommended thresholds and several contained multiple trichothecene variants. We obtained 64 isolates and identified diverse members of the Fusarium graminearum species complex (FGSC). However, the majority of the sampled isolates were Epicoccum spp. and may be linked to the country’s sorghum production. Our findings reveal that while Epicoccum alone causes minimal disease on wheat, its presence can have a small but synergistic impact on disease symptoms when F. graminearum has already infected. The FGSC species contributing to the outbreak include globally rare species, such as Fusarium aethiopicum. Additionally, we identified a FGSC lineage that did not match any known sequences. Whole-genome sequencing analysis confirmed this isolate as a new species in the FGSC that we have formally described as Fusarium kistlerii. SNP-based analyses suggest high clonal fraction among FGSC isolates, raising questions about a recent population expansion. The presence of globally rare species and suggestions of interspecies interactions in the 2022 Ethiopian outbreak, underscores the importance of addressing emerging threats in a globalized agricultural economy to secure food safety, food security, and global food equity amid a changing climate.