The Evolution of Lifestyles in Fusarium and Allied Genera

The Nectriaceae (Hypocreales, Sordariomycetes) includes saprobes, endophytes and numerous important pathogens, several of which are of high commercial interest. Members of Nectriaceae are circumscribed by having yellow, orange-red to purple, uniloculate ascomata, and phialidic asexual morphs. Presently there are more than 20 genera in Nectriaceae that have a fusarioid asexual morph. This group encompass diverse lifestyles, including plant, human, and animal pathogens or are associated with them, saprobes, lichenicolous species, endophytes, and mycophilic taxa. Following the one fungus = one name initiative, Fusarium was chosen over its sexual morph, Gibberella. Fusarium relates to the F3 clade sensu Crous et al. (2021). The fusarioid genera in Nectriaceae do not only differ in their sexual morphs, but also in their asexual morphology and biology, although their ecology has remained rather unclear. While genome data are available for numerous species, this has been mostly focused on Fusarium sensu stricto, as the genus encompasses most of the economically important species in this generic complex. To compliment this, we thus sequenced, assembled and annotated various genomes from type and reference strains spanning all fusarioid genera as well as closely related genera. Phylogenomic ancestral reconstructions of Fusarium and closely related genera in the present study showed that plant pathogenicity is ancestral to all fusarium-like and cylindrocarpon-like genera, and revealed multiple and frequent lifestyle transitions, with some exceptions. Although our results depict fusarioid genera as prolific generalists, several genera appear to be more specialised, being primarily plant pathogens, mycophilic, or insect associated, while endophytism evolved several times, and more recently in Fusarium.