Left – tree showing phylogenetic relationships of the 23 Fusarium species complexes and placement of F. poae within the F. sambucinum 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). Upper left – karyotype of F. poae. Upper right – culture of F. poae NRRL 26941 growing on potato dextrose agar medium. Middle– trichothecene mycotoxin biosynthetic loci in F. poae. Bottom – chemical structure of nivalenol, the most economically important trichothecene analog produced by F. poae. 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 referred to as species complexes (Geiser et al. 2021). Fusarium poae is a member of the Fusarium sambucinum species complex (FSAMSC), which is comprised of over 70 phylogenetically distinct species, including species that cause the economically important diseases including Fusarium head blight (FHB) of small grain cereals and ear rot of maize. During its evolutionary divergence, 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 late diverging complexes (4 – 7). Members of the FSAMSC have 4 – 7 chromosomes; F. poae has four (Waalwijk et al. 2018). Fusarium poae occurs on barley, oats and wheat, and is frequently recovered from wheat with symptoms of FHB. Fusarium poae produces trichothecenes (e.g., nivalenol), which are among the mycotoxins of most concern to agriculture. Strain NRRL 26941 was isolated from barley (Hordeum vulgare) kernels grown in the U.S. state of North Dakota.

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.

Vanheule, A., Audenaert, K., Warris, S., et al. 2016. Living apart together: crosstalk between the core and supernumerary genomes in a fungal plant pathogen. BMC Genomics. 17, 670.

Waalwijk C, Taga M, Zheng S-L, et al. 2018. Karyotype evolution in Fusarium. IMA Fungus 9:13-26. 10.5598/imafungus.2018.09.01.02