Left – tree showing phylogenetic relationships of the 23 Fusarium species complexes and placement of F. proliferatum within the F. fujikuroi 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 another strain of F. proliferatum (NRRL 66289). Middle right – culture of F. proliferatum ET1 growing on potato dextrose agar medium. Bottom - chemical structures of beauvericin and fumonisin B1, two mycotoxins produced by F. proliferatum. 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 proliferatum is a member of the Fusarium fujikuroi species complex, which consists of over 50 phylogenetically distinct species that have been further resolved into three major clades: the African Clade, American Clade and Asian Clade. Fusarium proliferatum is a member of the Asian Clade. During its evolutionary diversification Fusarium has undergone multiple chromosomal fusions and, 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 F. fujikuroi species complex typically have 12 chromosomes, but one of them is dispensable. Fusarium proliferatum causes economically important diseases of diverse crops, including maize, rice, date palm, asparagus, fig and onion. The fungus is one of the most significant causes of fumonisin mycotoxin contamination, and produces several other mycotoxins (e.g., beauvericin and moniliformin) whose impacts on health are not well understood. Strain ET1 was isolated from asymptomatic roots of the orchid Dendrobium moschatum grown in a greenhouse at the Tsitsin Central Botanical Garden in Moscow, Russia. The strain is unusual for F. proliferatum in that it produces the plant hormones gibberellins and has two paralogs of the gibberellin biosynthetic gene cluster (Niehaus et al. 2016).

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.

Niehaus EM, Munsterkotter M, Proctor RH, et al. 2016. Comparative "Omics" of the Fusarium fujikuroi species complex highlights differences in genetic potential and metabolite synthesis. Genome Biol Evol 8:3574-3599.