Mycologia, 95(4), 2003, pp. 630–636.
q 2003 by The Mycological Society of America, Lawrence, KS 66044-8897
Fusarium commune is a new species identified by morphological and
molecular phylogenetic data
Kerstin Skovgaard1
Søren Rosendahl
renberg and O’Donnell 1998). These cultures shared
several morphological characteristics typically found
in F. oxysporum, but they differed in that they produced polyphialides as well as long, slender monophialides.
Morphological characters frequently are homoplastic, and the circumscription of taxa, based on the
size and shape of conidia and conidiophores and the
color and texture of colonies, has resulted in an underestimation of species diversity within Fusarium
Link (Brayford 1996, O’Donnell 1996). Phylogenetic
species recognition, based on DNA sequence data
from multiple loci, allows greater numbers of species
to be distinguished than in the exclusive use of morphological features (Taylor et al 2000). Based on
morphological characters alone, between two and 10
taxa have been recognized in section Liseola (Booth
1971, Gerlach and Nirenberg 1982, Nelson et al
1983), four species in section Dlaminia (Kwasna et al
1991) and two species in section Elegans (Gerlach
and Nirenberg 1982). Using multigene genealogies,
O’Donnell et al (1998) recognized 36 species within
the Gibberella fujikuroi Saw. complex, represented by
part or all species of sections Liseola, Elegans and
Dlaminia. Over the past half-decade, combined molecular phylogenetic and morphological approaches
have been shown to be invaluable in the diagnosis of
fusaria (Aoki and O’Donnell 1999, Aoki et al 2001,
Gams et al 1999, Geiser et al 2001, Nirenberg and
O’Donnell 1998, O’Donnell et al 1998).
Evolutionary relationships among and within the
F. oxysporum species complex have been investigated
with multilocus DNA sequence data (Baayen et al
2000, Skovgaard et al 2001). Fusarium hostae Geiser,
a species causing root and crown rot of hosta, recently was discovered as the putative sister taxon of
F. redolens Wollenw., based on the analysis of partial
b-tubulin and translation elongation factor 1a sequences (Baayen et al 2001, Geiser et al 2001). In
this study we describe a new Fusarium species based
on morphology and phylogenetic analysis of partial
(EF-1a) and the mitochondrial small subunit ribosomal DNA (mtSSU rDNA) sequences.
Department of Mycology, University of Copenhagen,
Oester Farimagsgade 2D, 1353 Copenhagen K,
Denmark
Kerry O’Donnell
Microbial Properties Research Unit, National Center
for Agricultural Utilization Research, U.S. Department
of Agriculture, Agricultural Research Service, 1815 N.
University Street, Peoria, Illinois
Helgard I. Nirenberg
Institut für Pflanzenvirologie, Mikrobiologie und
biologische Sicherheit, Biologische Bundesanstalt für
Land- und Forstwirtschaft, Koenigin-Luise-Strasse 19,
14195 Berlin, Germany
Abstract: Fusarium commune sp. nov. was isolated
from soil and Pisum sativum in Denmark and several
widespread locations within the northern hemisphere from diverse substrates including white pine,
Douglas fir, carnation, corn, carrot, barley and soil.
Fusarium commune is characterized by and distinguished from its putative sister taxon, the F. oxysporum complex, in having long, slender monophialides
and polyphialides when cultured in the dark. Based
on the combined DNA sequence data from translation elongation factor 1a (EF-1a) and the mitochondrial small subunit ribosomal DNA (mtSSU rDNA),
the 15 isolates of F. commune analyzed formed a
strongly supported clade closely related to but independent of the F. oxysporum and Gibberella fujikuroi
species complexes.
Key words: gene genealogies, hyphomycetes, mitochondrial small subunit rDNA, phylogeny, soil fungi, translation elongation factor a
INTRODUCTION
During a study of Fusarium oxysporum Schlect.
emend. Snyder & Hansen occurring in pea fields in
Denmark, several fusaria were isolated that could not
be identified as any described species (Gerlach and
Nirenberg 1982, Booth 1971, Nelson et al 1983, Ni-
MATERIALS AND METHODS
Strains used in this study are listed in TABLE I together with
substrate and geographic origin. All isolates are stored in
Accepted for publication March 13, 2003.
1 Corresponding author. E-mail: kerstins@bot.ku.dk
630
TABLE I.
Strains of Fusarium used in this study
Sourcea
Species
NRRL 22172 (BBA 62264)
New Caledonia
B.C., Canada
OR, USA
Ontario, Canada
Ontario, Canada
Finland
Finland
Japan
Austria
Austria
The Netherlands
Denmark
Denmark
Denmark
Denmark
Denmark
SC, USA
Australia
Sweden
Denmark
Denmark
—
Denmark
Denmark
USA
Soil
Pseudotsuga menziesii (Mirb.) Frane
Pseudotsuga menziesii
Pinus strobes L.
Pinus strobes
Barley root (Hordeum vulgare L.)
Carrot root (Daucus carota L.)
River sediment
Zea mays L. leaf
Zea mays leaf
Dianthus caryophyllus L.
Pisum sativum L.
Soil
Soil
Soil
Soil
Hosta sp.
Musa sp.
Pisum sativum
Pisum sativum
Soil
—
Pisum sativum
Pisum sativum
Zea mays
Germany
Zea mays
SP. NOV.
25174 (FRC M-1425 5 BBA 65829)
22900 (BCRI P4C2P17A)
22903b (BCRI 3139)
25043 (BBA 69585)
25049 (BBA 69586)
26897 (ARCF 93144)
26898d (ARCF 94193 5 BBA 71641)
28058 (FRC 0-1173)
28180 (MA 1208)
28182 (MA 1210)
28387d (PD 90/1377)
31076bcd (AAS 156 5 BBA 71639)
31077d (AAS 345)
31079d (AAS 362)
31080 (AAS 363 5 BBA 71640)
31081 (AAS 364)
29889 (FRC 0-2074)
25603 (HCK A2)
31073 (Bødker L5)
31074 (AAS 112)
31078 (AAS 350)
22057 ( JFL 4853)
31075 (AAS 127)
31255 (AAS 120)
22016 ( JFL 2192)
FUSARIUM COMMUNE,
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
NRRL
ET AL:
beomiforme
commune
commune
commune
commune
commune
commune
commune
commune
commune
commune
commune
commune
commune
commune
commune
hostae
oxysporum
oxysporum
oxysporum
oxysporum
proliferatum (Matsushima) Nirenb.
redolens
redolens
subglutinans (Wollenw. &
Reinking) Nelson et al.
F. verticillioides (Sacc.) Nirenb.
Host/Substrate
SKOVGAARD
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
F.
Geographic origin
a AAS, K. Skovgaard, Botanical Institute, Department of Mycology, University of Copenhagen, Copenhagen, Denmark; ARCF, T. Yli-Mattila, Agricultural Research
Centre of Finland, Jokioinen, Finland; BBA, Institut für Pflanzenvirologie, Mikrobiologi und biologische Sicherheit, Biologische Bundesanstalt für Land- und Forstwirtschaft, Berlin, Germany; BCRI, British Columbia Research Inc., Vancouver, Canada; Bødker, L. Bødker, Danmarks JordbrugsForskning, Flakkebjerg, Denmark; FRC,
Fusarium Research Center, Penn State University, University Park, USA; HCK, C. Kistler, USDA, St. Paul, USA; JFL, J. F. Leslie, Department of Plant Pathology, Kansas
State University, Manhattan, USA; MA, Vienna Institute of Applied Microbiology (VIAM), Vienna, Austria; NRRL, National Center for Agricultural Utilization Research,
Peoria, USA; PD, Plantenziektenkundige Dienst, Wageningen, The Netherlands.
b Pathogenicity tested at BBA.
c Ex-type.
d Isolates examined.
631
632
MYCOLOGIA
liquid nitrogen at the National Center for Agricultural Utilization Research, Peoria, IL (NRRL). The ex-type culture
of Fusarium commune NRRL 31076 also is stored in soil vials
and as freeze-dried cultures at the Institut für Pflanzenvirologie, Mikrobiologie und biologische Sicherheit, Biologische Bundesanstalt für Land- und Forstwirtschaft culture collection (BBA), Berlin, Germany, as well as in glycerol at280
C at the Botanical Institute, Department of Mycology, University of Copenhagen, Copenhagen, Denmark (AAS).
Morphological examination. Cultures were grown on potato-dextrose agar (PDA; Difco, Detroit, Michigan) at 20 C in
the dark. Colony colors were determined using the Methuen Handbook of Colour (Kornerup and Wanscher 1978).
Microscopic characters were studied after 10 to 14 days’
growth on synthetic low nutrient agar (SNA) overlain with
a 1 3 2 cm piece of sterile filter paper (Nirenberg 1990).
Characteristic morphological traits were photographed and
measurements of conidia, chlamydospores and phialides
were made after the cultures were incubated either in the
dark or under continuous black light (Philips TLD 18w/
08) (Nirenberg 1990). At least 30 randomly selected 1-, 3and 5-septate conidia were measured and their mean values
and ranges (shown in brackets) were determined.
Pathogenicity test. Two isolates of Fusarium commune,
NRRL 22903 and 31076, were tested for their pathogenicity
toward Pinus sylvestris L. and Picea rubens Sarg. These conifer species are hosts of F. blasticola Rostr., a morphologically similar species initially thought to be conspecific with
F. commune (see below). From 14-day-old SNA cultures of
these two isolates, five 10 mm2 pieces were transferred separately to each of seven Erlenmeyer flasks filled with a sterile peat-straw-sand mixture (2:2:1). Each culture was allowed to grow through the mixture at 20 C. After 19 d the
inoculated soil was mixed with a commercial soil, TKS 1
(Flora Gard, Berlin, Germany), and sand (2:3:1). The inoculum of each fungus was used to fill 20 plastic pots (9 cm
in diameter). Eight-week-old seedlings of each of the conifer species were planted individually in 10 pots. Negative
controls treated the same way but lacked fungi. The pots
were placed in a greenhouse at 15 C to 18 C. After three
months the temperature was raised to 25 C for the next two
months. Symptoms were evaluated after five months’ incubation.
Sequencing and phylogenetic analysis. Isolates were grown
as shake cultures (200 rpm) in a yeast-malt broth (0.3%
yeast extract, 0.3% malt extract, 0.5% peptone, 2% glucose)
2–3 days at room temperature. Genomic DNA was extracted
from lyophilized mycelium by the CTAB-method (O’Donnell
and Cigelnik 1997). Amplification and sequencing of the
mtSSU rDNA and EF-1a genes was carried out employing
the primers and thermocycling parameters described by
White et al (1990) and O’Donnell et al (2000). PCR products were purified with GeneClean II (Bio 101, La Jolla,
CA). Cycle sequencing products were spun through Sephadex G-50 columns (Pharmacia, Piscataway, NJ) to remove unincorporated dye-labeled nucleotides and sequenced on an automated ABI 377 sequencer (Perkin-Elmer, Foster City, CA).
Sequencher 3.0 (GeneCodes, Ann Arbor, MI) and Bioedit (Hall 1999) were used to edit and align the sequence
data. The final alignment is available through TreeBASE.
Sequences were deposited in GenBank under accessions
numbers AF362261 to AF362292. Sequence data from EF1a and mtSSU rDNA were tested for combinability with
the partition homogeneity test implemented in PAUP
4.0b2 (Swofford 1999). Branch and bound searches were
performed with default options. Alignment gaps were
treated as missing data and 1000 parsimony bootstrap replications were conducted to test clade support.
RESULTS
Fusarium commune Skovgaard, O’Donnell et Nirenberg, sp. nov.
FIGS. 1–6
Coloniae in PDA in dies radium 4.6–5.6 mm expandentes, temperatura 20 C in obscuritate. Mycelium aerium album usque ad aurantiaco-album, lanosum usque ad byssaceum. Color coloniarum in reverso griseo-fulvidus, nonnumquam griseo-violaceus.
Odor insensibilis. Sporulatio in mycelio aerio praecox in SNA, conidia capitulis aggregata. Sporodochia
post 10 dies formata sub luce nigra continua. Conidiophora in mycelio aerio prostrata. Phialides cylindricae pro parte maxima monophialidicae nonnumquam polyphialidicae; monophialides seu breves
(ca 17 mm) seu longiores (ad 60 mm), 3.5–4.0 mm
latae; polyphialides not magis quam 30 mm longae.
Conidia in mycelio aerio oblonge ovalia, recta vel
curvata, plerumque non-septata, aliquando 1- vel 2septata, conidia non-septata: (4.0–) 5.5–7.7 (-8.0) 3
(2.0–) 2.5–3.5 (–4.0) mm; conidia sporodochialia
plerumque falcata et 3-septata: (22–) 24–30 (–38) 3
3.8–4.1 mm obscuritate, (32–) 34–42 (–50) 3 3.8–4.2
mm sub luce nigra continua; chlamydosporae 8–12
mm diam, leves, singulares vel binae. Teleomorphosis
ignota. Holotypi origo geographica in Dania, in
humo. Ex holotypo culturae NRRL 31076 5 BBA
71639 5 AAS 156.
HOLOTY PUS. Colonia sicca BBA 71639, deposita
in herb. B.
Colonies with a radial growth rate of 5.1 mm per
day on PDA at 20 C in the dark. Aerial mycelium
white to orange white, generally abundant, densely
floccose to fluffy, later resupinate in degenerated cultures. Colony reverse grayish yellow with magenta to
dull violet pigmentation, often in rings. The grayish
magenta was dominant in older and degenerate cultures. Odor not detectable. Sporulation starting early
in aerial mycelium, abundant after 10 days on SNA.
0-septate conidia produced in slimy droplets and sporodochia, typically formed after 10 days under continuous black light. Conidiophores consisting of
short monophialides up to 17 mm long and 4.0 mm
wide, or longer and more slender monophialides up
SKOVGAARD
ET AL:
FUSARIUM COMMUNE,
SP. NOV.
633
FIGS. 1–6. Fusarium commune (Scale bar 5 25 mm). 1. Polyphialidic conidiophore. 2. Polyphialidic and monophialidic
conidiophores of the aerial mycelium. 3. Polyphialidic and long monophialidic conidiophores of the aerial mycelium. 4.
Long sporodochial conidia. 5. Chlamydospores. 6. Sporodochial conidia. Figs. 1–3, 5 from cultures maintained in the dark,
Figs. 4, 6 from cultures maintained under continuous black light.
to 60 mm long and 3.5 mm wide. Polyphialides up to
30 mm long and 3.5 mm wide, appearing in cultures
incubated in the dark. Aerial conidia mostly 0-septate, cylindrical, straight to slightly curved, measuring
(4.0–) 5.5–7.7 (–8.0) 3 (2.0–) 2.5–3.5 (–4.0) mm. Conidia borne in sporodochia typically fusiform with a
slightly curved apical cell and a foot-shaped basal
cell, bending equally toward both ends. Three-sep-
tate conidia (22–) 24–30 (–38) 3 3.8–4.1 mm formed
in the dark and under continuous black light (32–)
34–42 (–50) 3 3.8–4.2 mm, five-septate conidia under
continuous black light (52–) 56–60 (–64) 3 (3.8–)
3.9–4.6 (–5.0) mm. Chlamydospores 8–12 mm diam,
smooth, intercalary or terminal, and produced singly
or in pairs. Cardinal temperatures: 7.5 C, 27.5 C and
35.0 C. Teleomorph unknown.
634
MYCOLOGIA
FIG. 7. Single most-parsimonious phylogram based on the combined analysis of EF-1a and mtSSU rDNA gene sequences.
Bootstrap frequencies from 1000 replications are given above nodes. Consistency index 5 0.80, retention index 5 0.89, tree
length 5 285.ol6
Sequence data. Two substitutions were found within
the alignment of EF-1a (572 bp) and mtSSU rDNA
(698 bp) from the 15 isolates of F. commune. Results
of the partition homogeneity test indicated that the
EF-1a and mtSSU rDNA partitions could be combined (P 5 0.267). A branch and bound search of
the combined dataset, rooted with sequences of F.
beomiforme Nelson et al, yielded a single most-parsi-
monious tree of 285 steps (FIG. 7, consistency index
5 0.80, retention index 5 0.89). The 15 isolates of
F. commune formed a strongly supported monophyletic group (bootstrap 5 100%).
Pathogenicity test. Disease symptoms were not observed after five months incubation of Pinus sylvestris
SKOVGAARD
ET AL:
FUSARIUM COMMUNE,
and Picea rubens with strains of F. commune (NRRL
22903 and 31076).
SP. NOV.
635
(Ueno et al 1977, Marasas et al 1984), studies are in
progress to elucidate the mycotoxin potential of F.
commune.
DISCUSSION
Fusarium commune and F. oxysporum are morphologically similar in that they both produce conidia on
short monophialides in false heads on the aerial mycelium and chlamydospores singly or in pairs.
Unique features of F. commune include long, slender
monophialides in addition to the occasional production of polyphialides. Ten of the 15 strains of F. commune used in this study were identified originally as
F. oxysporum.
Four of the 15 isolates studied (NRRL 22900,
25043, 28058, 31080) produced longer sporodochial
conidia than the type isolate, and the other isolates
in the dark and under black light. In these four
strains, 3-septate conidia measured (36–) 40–50 (–52)
3 3.7–4.0 mm in the dark and (36–) 44–56 (–60) 3
3.8–4.1 mm under continuous black light; 5-septate
conidia were (44–) 52–58 (–60) 3 3.9–4.1 mm under
continuous black light.
Little variation in EF-1a and mtSSU rDNA sequences was obser ved within F. commune, even
though the 15 strains were isolated from a wide range
of substrates and geographic locations throughout
the northern hemisphere. No relationship was observed between the minor sequence differences in
the F. commune clade and differences in macroconidial morphology. The molecular phylogenetic analysis identified F. commune as a putative sister group to
the F. oxysporum complex, a result consistent with the
high morphological similarity of these taxa (FIG. 7).
Fusarium redolens as well as the newly described F.
hostae (Geiser et al 2001) formed a sister group to
the rest of the ingroup taxa.
Fusarium commune was considered to be conspecific with F. blasticola (Wollenweber and Reinking
1935), a species isolated originally from seedlings of
Pinus montana Lamarck and described as Fusoma
parasitica Tub. (Tubeuf 1895). Although conidia
were not observed in the type material of F. blasticola,
the description of this species as possessing slender
(3.5 mm) 3-septate conidia that occur rarely in sporodochia (Hartig 1892, Wollenweber and Reinking
1935) is inconsistent with our observations of F. commune. In addition, results of the infection tests indicate that F. commune is not pathogenic to seedlings
of Pinus sylvestris and Picea rubens, two of the hosts
of F. blasticola. Collectively, these results support the
separation of F. commune and F. blasticola. The phytopathological role of F. commune on other hosts, if
any, is still unknown. Given that a culture extract of
F. commune NRRL 28058 was reported to be toxigenic
ACKNOWLEDGMENTS
Thanks are due to Kenn Kristiansen for expert laboratory
assistance, Lise Fabricius and Leif Bolding for help in preparing the figures, and the culture collections and individuals cited in TABLE I for providing strains. The U.S.D.A.
neither guarantees nor warrants the standard of the product, and the use of the name U.S.D.A. implies no approval
of the product to the exclusion of others that may also be
suitable.
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