Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user’s needs and established successful practice. In 2013, the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani species complex (FSSC). Subsequently, this concept was challenged in 2015 by one research group who proposed dividing the genus Fusarium into seven genera, including the FSSC described as members of the genus Neocosmospora, with subsequent justification in 2018 based on claims that the 2013 concept of Fusarium is polyphyletic. Here, we test this claim and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a genus Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students, and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species described as genus Neocosmospora were recombined in genus Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural, and practical taxonomic option available.

The Fusarium sambucinum species complex (FSAMSC) is one of the most taxonomically challenging groups of fusaria, comprising prominent mycotoxigenic plant pathogens and other species with various lifestyles. Among toxins produced by members of the FSAMSC, trichothecenes pose the most significant threat to public health. Herein a global collection of 171 strains, originating from diverse hosts or substrates, were selected to represent FSAMSC diversity. This strain collection was used to assess their species diversity, evaluate their potential to produce trichothecenes, and cause disease on wheat. Maximum likelihood and Bayesian analyses of a combined 3-gene dataset used to infer evolutionary relationships revealed that the 171 strains originally received as 48 species represent 74 genealogically exclusive phylogenetically distinct species distributed among six strongly supported clades: Brachygibbosum, Graminearum, Longipes, Novel, Sambucinum, and Sporotrichioides. Most of the strains produced trichothecenes in vitro but varied in type, indicating that the six clades correspond to type A, type B, or both types of trichothecene-producing lineages. Furthermore, five strains representing two putative novel species within the Sambucinum Clade produced two newly discovered type A trichothecenes, 15-keto NX-2 and 15-keto NX-3. Strains of the two putatively novel species together with members of the Graminearum Clade were aggressive toward wheat when tested for pathogenicity on heads of the susceptible cultivar Apogee. In planta, the Graminearum Clade strains produced nivalenol or deoxynivalenol and the aggressive Sambucinum Clade strains synthesized NX-3 and 15-keto NX-3. Other strains within the Brachygibbosum, Longipes, Novel, Sambucinum, and Sporotrichioides Clades were nonpathogenic or could infect the inoculated floret without spreading within the head. Moreover, most of these strains did not produce any toxin in the inoculated spikelets. These data highlight aggressiveness toward wheat appears to be influenced by the type of toxin produced and that it is not limited to members of the Graminearum Clade.

Recent studies on multiple continents indicate members of the Fusarium tricinctum species complex (FTSC) are emerging as prevalent pathogens of small-grain cereals, pulses, and other economically important crops. These understudied fusaria produce structurally diverse mycotoxins, among which enniatins (ENNs) and moniliformin (MON) are the most frequent and of greatest concern to food and feed safety. Herein a large survey of fusaria in the Fusarium Research Center and Agricultural Research Service culture collections was undertaken to assess species diversity and mycotoxin potential within the FTSC. A 151-strain collection originating from diverse hosts and substrates from different agroclimatic regions throughout the world was selected from 460 FTSC strains to represent the breadth of FTSC phylogenetic diversity. Evolutionary relationships inferred from a five-locus dataset, using maximum likelihood and parsimony, resolved the 151 strains as 24 phylogenetically distinct species, including nine that are new to science. Of the five genes analyzed, nearly full-length phosphate permease sequences contained the most phylogenetically informative characters, establishing its suitability for species-level phylogenetics within the FTSC. Fifteen of the species produced ENNs, MON, the sphingosine analog 2-amino-14,16-dimethyloctadecan-3-ol (AOD), and the toxic pigment aurofusarin (AUR) on a cracked corn kernel substrate. Interestingly, the five earliest diverging species in the FTSC phylogeny (i.e., F. iranicum, F. flocciferum, F. torulosum, and Fusarium spp. FTSC 8 and 24) failed to produce AOD and MON, but synthesized ENNs and/or AUR. Moreover, our reassessment of nine published phylogenetic studies on the FTSC identified 11 additional novel taxa, suggesting this complex comprises at least 36 species.

Multilocus DNA sequence data were used to investigate species identity and diversity in two sister clades, the Fusarium concolor (FCOSC) and F. babinda species complexes. Of the 109 isolates analyzed, only 4 were received correctly identified to species and these included 1/46 F. concolor, 1/31 F. babinda, and 2/3 F. anguioides. The majority of the F. concolor and F. babinda isolates were received as F. polyphialidicum, which is a heterotypic synonym of the former species. Previously documented from South America, Africa, Europe, and Australia, our data show that F. concolor is also present in North America. The present study expands the known distribution of F. babinda in Australia to Asia, Europe, and North America. The molecular phylogenetic results support the recognition of a novel Fusarium species within the FCOSC, which is described and illustrated here as F. austroafricanum, sp. nov. It was isolated as an endophyte of kikuyu grass associated with a putative mycotoxicosis of cattle and from plant debris in soil in South Africa. Fusarium austroafricanum is most similar morphologically to F. concolor and F. babinda but differs from the latter two species in producing (i) much longer macroconidia in which the apical cell is blunt to slightly papillate and the basal cell is only slightly notched and (ii) macroconidia via microcycle conidiation on water agar. BLASTn searches of the whole genome sequence of F. austroafricanum NRRL 53441 were conducted to predict mycotoxin potential, using genes known to be essential for the synthesis of several mycotoxins and biologically active metabolites. Based on the presence of intact gene clusters that confer the ability to synthesize mycotoxins and pigments, we analyzed cracked corn kernel cultures of F. austroafricanum via liquid chromatography–mass spectrometry (LC-MS) but failed to detect these metabolites in vitro.

We report on the discovery and characterization of a novel Fusarium species that produced yellow-orange pseudoflowers on Xyris spp. (yellow-eyed grass; Xyridaceae) growing in the savannas of the Pakaraima Mountains of western Guyana. The petaloid fungal structures produced on infected plants mimic host flowers in gross morphology. Molecular phylogenetic analyses of full-length RPB1 (RNA polymerase largest subunit), RPB2 (RNA polymerase second largest subunit), and TEF1 (elongation factor 1-α) DNA sequences mined from genome sequences resolved the fungus, described herein as F. xyrophilum, sp. nov., as sister to F. pseudocircinatum within the African clade of the F. fujikuroi species complex. Results of a polymerase chain reaction (PCR) assay for mating type idiomorph revealed that single-conidial isolates of F. xyrophilum had only one of the MAT idiomorphs (MAT1-1 or MAT1-2), which suggests that the fungus may have a heterothallic sexual reproductive mode. BLASTn searches of whole-genome sequence of three strains of F. xyrophilum indicated that it has the genetic potential to produce secondary metabolites, including phytohormones, pigments, and mycotoxins. However, a polyketide-derived pigment, 8-O-methylbostrycoidin, was the only metabolite detected in cracked maize kernel cultures. When grown on carnation leaf agar, F. xyrophilum is phenotypically distinct from other described Fusarium species in that it produces aseptate microconidia on erect indeterminate synnemata that are up to 2 mm tall and it does not produce multiseptate macroconidia.

In this study, DNA sequence data were used to characterize 290 Fusarium strains isolated during a survey of root-colonizing endophytic fungi of agricultural and nonagricultural plants in northern Kazakhstan. The Fusarium collection was screened for species identity using partial translation elongation factor 1-α (TEF1) gene sequences. Altogether, 16 different Fusarium species were identified, including eight known and four novel species, as well as the discovery of the phylogenetically divergent F. steppicola lineage. Isolates of the four putatively novel fusaria were further analyzed phylogenetically with a multilocus data set comprising partial sequences of TEF1, RNA polymerase II largest (RPB1) and second-largest (RPB2) subunits, and calmodulin (CaM) to assess their genealogical exclusivity. Based on the molecular phylogenetic and comprehensive morphological analyses, four new species are formally described herein: F. campestre, F. kazakhstanicum, F. rhizicola, and F. steppicola.