Left – tree showing phylogenetic relationships of the 23 Fusarium species complexes and placement of F. avenaceum within the F. tricinctum species complex. In the tree, species complex names are abbreviated using specific epithets of the species after which the complexes are named (e.g., the F. sambucinum species complex is abbreviated as sambucinum). Middle left – karyotype of F. avenaceum. Middle right – culture of F. avenaceum strain NRRL 54939 growing on potato dextrose agar medium. Bottom – chemical structures of enniatins and moniliformin, two mycotoxins produced by F. avenaceum. Image credit: Robert H. Proctor, Amy McGovern and Crystal Probyn.

Fusarium (family Nectriaceae) is a species-rich fungal genus that poses a dual threat to agriculture because many species cause destructive crop diseases and/or contaminate infected crops with toxic secondary metabolites (mycotoxins) that are health hazards to humans and other animals. Some Fusarium mycotoxins are frequent contaminants of dried distillers’ grains, coproducts of grain-based ethanol production used as a protein-rich livestock feed. In addition, some species of Fusarium are pathogens of energy crops such as corn and sugar cane. Some species can also exist as endophytes in plants, including some bioenergy crops.

DNA-based phylogenetic analyses have resolved Fusarium into 23 multi-species lineages known as species complexes (Geiser et al. 2021). Fusarium avenaceum is a member of the Fusarium tricinctum species complex (FTSC), which consists of at least 36 phylogenetically distinct species (Laraba et al. 2022). During its evolutionary diversification, Fusarium has undergone multiple chromosomal fusions. As a result, members of early diverging species complexes tend to have more chromosomes (15 – 20) than members of later diverging complexes (4 – 7). Four members of the FTSC that have been examined, including F. avenaceum, have 9 or 10 chromosomes. Some members of the FTSC are emerging as significant pathogens of multiple economically important crops, including small-grain cereals, dried legumes and apple. Although members of the complex do not produce the major Fusarium mycotoxins fumonisins or trichothecenes, at least some produce enniatins and moniliformin, mycotoxins whose impacts on health are poorly understood. In addition, F. avenaceum and some other members of FTSC produce the sphinganine-analog metabolite 2-amino-14,16-dimethyl-octadecan-3-ol, which most likely disrupts sphingolipid metabolism in a manner similar to fumonisins. Fusarium avenaceum strain NRRL 54939 (Fa05001) was isolated from barley (Hordeum vulgare) grown in Finland.

References:
Geiser DM, Al-Hatmi A, Aoki T, et al. 2021. Phylogenomic analysis of a 55.1 kb 19-gene dataset resolves a monophyletic Fusarium that includes the Fusarium solani Species Complex. Phytopathology 111: 1064-1079.

Laraba I, Busman M, Geiser DM, O'Donnell K. 2022. Phylogenetic diversity and mycotoxin potential of emergent phytopathogens within the Fusarium tricinctum species complex. Phytopathology 112:1284-1298.

Lysoe E, Harris LJ, Walkowiak S, et al. 2014. The genome of the generalist plant pathogen Fusarium avenaceum is enriched with genes involved in redox, signaling and secondary metabolism. PLoS One 9:e112703.