Left – tree showing phylogenetic relationships of the 23 Fusarium species complexes and placement of F. pseudograminearum within the F. solani 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 right – culture of F. pseudograminearum NRRL 62612 (= CS3096) growing on potato dextrose agar medium. Bottom right – chemical structures of 3-acetyldeoxynivalenol and zearalenone, two mycotoxins produced by F. pseudograminearum. 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, or species complexes (Geiser et al. 2021). Fusarium pseudograminearum is a member of the Fusarium sambucinum species complex (FSAMSC), which is comprised of over 70 phylogenetically distinct species that tend to cause diseases and mycotoxin contamination of cereal crops. 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 later diverging complexes (4 – 7). Members of the FSAMSC typically have 4 – 7 chromosomes; F. pseudograminearum has 4. This species tends to occur in arid and semi-arid regions of the world, including parts of Africa, Australia, the Pacific Northwest in the U.S., and southwestern Canada. In these regions, F. pseudograminearum causes crown rot of cereal crops and wild grasses. Like other members of the FSAMSC, the fungus can produce trichothecene mycotoxins. Strain NRRL 62612 (= CS3096) was isolated from wheat grown in New South Wales, Australia (Gardiner et al. 2012).

References:

Geiser DM, Al-Hatmi A, Aoki 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.

Gardiner DM, McDonald MC, Covarelli L, et al. 2012. Comparative pathogenomics reveals horizontally acquired novel virulence genes in fungi infecting cereal hosts. PLoS Pathog 8:1-22.