Pitt JI, Lantz H, Petterson OV, Leong SL.. Xerochrysium gen. nov. and Bettsia, genera encompassing xerophilic species of Chrysosporium. IMA Fungus 4: 229-241

Abstract

On the basis of a study of ITS sequences, Vidal et al. (Rev. Iber. Micol.
17: 22, 2000) recommended that the genus Chrysosporium be restricted to species belonging to Onygenales. Using nrLSU genes, we studied the majority of clades examined by Vidal et al. and showed that currently accepted species in Chrysosporium phylogenetically belong in six clades in three orders. Surprisingly, the xerophilic species of Chrysosporium, long thought to be a single grouping away from the majority of Chrysosporium species, occupy two clades, one in Leotiales, the other in Eurotiales. Species accepted in Leotiales are related to the sexual genus Bettsia. One is the type species B. alvei, and related asexual strains classified as C. farinicola, the second is C. fastidium transferred to Bettsia as B. fastidia. Species in the Eurotiales are transferred to Xerochrysium gen. nov., where the accepted species are X. xerophilum and X. dermatitidis, the correct name for C. inops on transfer to Xerochrysium. All accepted species are extreme xerophiles, found in dried and concentrated foods.

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volume 4 · no. 2
INTRODUCTION
The genus Chrysosporium was revived by Carmichael
(1962) as a way to rationalise the taxonomy of a number of
genera of hyphomycetes characterised by the production
of aleurioconidia “on undifferentiated hyphae either at
the tip, along the sides, or in an intercalary position.” The
aleurioconidia “were released by the disintegration of
part, or all, of the spore-bearing mycelium” (Carmichael
1962). Although “aleurioconidium” is considered to be an
obsolete term, it remains the most precise available for
thick-walled conidia produced on pedicels along a stipe,
seceding only with difculty. Many of the species included in
Chrysosporium by Carmichael were of medical importance,
being dermatophytic or keratinolytic or both. However, one
new species described by Carmichael, C. inops, was isolated
from orange concentrate, so was likely to be xerophilic.
Some species, including C. inops, also produce thick-walled
intrahyphal conidia, both swollen cells (chlamydoconidia) and
unswollen cells (arthroconidia), which intergrade (Carmichael
1962, Barron 1968).
Pitt (1966) described two new species of Chrysosporium,
C. fastidium and C. xerophilum, from dried fruit: both
appeared to be related to C. inops. These species were
subsequently shown to be among the most xerophilic
organisms known, capable of growth below 0.7 water
activity (aw) (Pitt & Christian 1968, Pitt 1975). In the following
years, it was considered that Carmichael’s concept of
Chrysosporium was too broad: some genera including
Sporothrix, Sporotrichum, and Geomyces were separated
out again. Sporothrix is a medically important dermatophyte
(de Hoog et al. 2000), Sporotrichum has been restricted
to the asexual states of some lignicolous basidiomycetes
(Stalpers 1984), and Geomyces is a genus of saprophytes
(Barron 1968) and also includes a xerophilic species
(Hocking & Pitt 1988).
Van Oorschot (1980) monographed Chrysosporium,
retained Carmichael’s concept of the genus, and accepted 22
species. However, the medium used in descriptions by van
Oorschot (1980) was a cherry decoction agar, of unspecied
but undoubtedly quite high aw, so that growth of the xerophilic
species was far from optimal. The basic circumscription of
Chrysosporium still included most hyphomycete fungi that
produce aleurioconidia.Skou (1972) described a new sexual
genus, Bettsia. This includes a single species, B. alvei, which
produces a xerophilic Chrysosporium asexual morph, C.
farinicola (Skou 1975). Bettsia alvei produces small, dark,
distinctive cleistothecia, different from sexual morphs related
to other Chrysosporium species. Skou (1992) described
several new xerophilic species and varieties of Chrysosporium
from mason bees (Osmia spp.) and beehives.
Using ribosomal ITS sequence data, Vidal et al. (2000)
divided Chrysosporium into nine species groups and
concluded that this genus should be restricted to asexual
species in Onygenales that possess keratinophilic but not
cellulolytic capabilities.
doi:10.5598/imafungus.2013.04.02.08 IMA FUNGUS · VOLUME 4 · NO 2: 229–241
Xerochrysium gen. nov. and Bettsia, genera encompassing
xerophilic species of Chrysosporium
John I. Pitt1, Henrik Lantz2,3, Olga Vinnere Pettersson2,4, and Su-lin L. Leong2
1CSIRO Animal, Food and Health Sciences, P.O. Box 52, North Ryde, NSW 1670, Australia; corresponding author e-mail: John.Pitt@csiro.au
2Swedish University of Agricultural Sciences, Uppsala BioCenter, Dept of Microbiology, Box 7025, Uppsala 75007, Sweden
3Uppsala University, Department of Medical Biochemistry and Microbiology, Box 582, 75123 Uppsala
4Uppsala University, Immunology, Genetics and Pathology, Rudbecklaboratoriet, 75185 Uppsala
Abstract: On the basis of a study of ITS sequences, Vidal et al. (Rev. Iber. Micol. 17: 22, 2000) recommended
that the genus Chrysosporium be restricted to species belonging to Onygenales. Using nrLSU genes, we studied
the majority of clades examined by Vidal et al. and showed that currently accepted species in Chrysosporium
phylogenetically belong in six clades in three orders. Surprisingly, the xerophilic species of Chrysosporium, long
thought to be a single grouping away from the majority of Chrysosporium species, occupy two clades, one in
Leotiales, the other in Eurotiales. Species accepted in Leotiales are related to the sexual genus Bettsia. One is the
type species B. alvei, and related asexual strains classied as C. farinicola, the second is C. fastidium transferred
to Bettsia as B. fastidia. Species in the Eurotiales are transferred to Xerochrysium gen. nov., where the accepted
species are X. xerophilum and X. dermatitidis, the correct name for C. inops on transfer to Xerochrysium. All
accepted species are extreme xerophiles, found in dried and concentrated foods.
Article info: Submitted: 18 August 2013; Accepted: 12 November 2013; Published: 19 November 2013.
Key words:
Eurotiales
food spoilage
Leotiales
molecular systematics
Onygenales
taxonomy

Pitt et al.
ARTICLE
230 ima fUNGUS
Our study of the extremely xerophilic ascomycete
Xeromyces bisporus indicated a close relatedness to
the xerophilic Chrysosporium species C. xerophilum and
C. inops. Phylogenetic analysis of the 28S rRNA gene
securely placed these species within Eurotiales, as strictly
asexual species (Pettersson et al. 2011). Chrysosporium
xerophilum is capable of more rapid growth over a wider aw
range than C. inops (Leong et al. 2011).
This paper reports a critical assessment of the
xerophilic species currently classied in Chrysosporium, i.e.
C. fastidium, C. farinicola, C. inops, and C. xerophilum,
together with the seven species described by Skou (1992).
MATERIALS AND METHODS
Cultural studies
Culture conditions
The xerophilic species studied grow very poorly, if at all, on
conventional media such as Czapek yeast extract agar (CYA)
or malt extract agar (MEA; Pitt & Hocking 2009). Optimal
growth occurs on very concentrated media, such as malt
extract yeast extract 50 % glucose agar (MY50G, 0.89 aw).
Taxonomic descriptions are therefore based on growth on
that medium (Pitt & Hocking 2009). Plates were three-point
inoculated with a needle-point of dry spores, and incubated
at 25 °C for 7 d, colonies were measured, and plates were
then reincubated for a further 7 d. Microscopical observations
were made at both times.
Growth and morphology of cultures at 25 °C were also
examined on G25N and Casein Czapek 50G agar after 14
d, the latter previously used for differentiating foodborne
Chrysosporium species (Kinderlerer 1995).
Effect of water activity and temperature on growth
rate
Agar media based on MY50G were prepared at 0.99, 0.89,
0.78, 0.73 and 0.71 aw. At the two lowest water activities,
glucose and fructose were mixed in equal amounts. The water
activities of the media were monitored at the beginning and
end of the trial using the dew point technique in the AquaLab
CX-2 (Decagon Devices, Pullman, WA, USA). Mycelial
suspensions were prepared in sterile 50 % glycerol from
cultures grown on MY50G at 25 °C for 3 wk. Triplicate plates
were single point inoculated with 5 µL mycelial suspension
and incubated at 20, 25, 30 and 37 °C for 50 d. Plates were
wrapped in polyethylene lm (household cling lm) to prevent
evaporation and placed in double zip-lock polyethylene bags
in stacks no higher than six plates tall. To calculate the linear
growth rate of the strains, colony diameters were measured
on two perpendicular axes regularly at appropriate intervals,
and the mean diameters recorded.
Molecular studies
Sequences used
The phylogenetic relationships of the species studied
were assessed by analysis of 28S rRNA sequences,
including representative species from the majority of clades
described by Vidal et al. (2000). Ex-type strains were used
where available, obtained from CBS (KNAW-CBS Fungal
Biodiversity Centre, Utrecht), and FRR (CSIRO Animal,
Food and Health Sciences, North Ryde, NSW). Additional
sequences were also downloaded from GenBank based
on two principles. First, conserved regions of nrLSU were
extracted from Chrysosporium species representing each
strongly supported clade in Vidal et al. (2000) and used to
nd similar sequences in GenBank with BLAST (Altschul
et al. 1990). Second, to be able to place the xerophilic
Chrysosporium species to order and class, a wide sample of
species representing most ascomycete orders and classes
was included. Accession numbers for these additional
sequences are noted in the TreeBASE le (see Results,
Phylogenetic analysis).
Sequencing
For DNA extraction, nonxerophilic strains were grown on
MEA and xerophilic strains on MY50G at 25 °C for 2 wk.
Fresh mycelia were harvested by scraping colony surfaces
into Eppendorf tubes containing 200 mM TRIS pH 8.5, 250
mM NaCl, 25 mM EDTA pH 8.0 and 1 % SDS. Mycelia were
then mechanically sheared using a VWR pestle-homogeniser
(Argos Technologies, Elgin, IL). An equal volume of phenol:
chloroform: isoamyl alcohol (25:24:1) was added, after which
tubes were centrifuged at 13 000 g, for 20 min at 4 °C. The
aqueous phase was collected and DNA precipitated by
adding an equal volume of ice cold isopropanol, followed by
10 min incubation at -20 °C. The pellets were collected by
centrifugation at 8,000 g, washed with 95 % ethanol, dried,
dissolved in Tris EDTA buffer and quantied by NanoVue
machine (GE Lifesciences, Uppsala).
PCR was performed with primers 5.8SR and LR6 (Vilgalys
& Hester 1990) using Phusion High Fidelity DNA polymerase
(Finnzymes, Helsinki) under conditions recommended by the
manufacturer.
Before sequencing, the amplied fragments were
puried using the QIAquick PCR Purication kit (QiaGen,
Hilden, Germany). Sequencing reactions were performed
at Macrogen (Seoul, Korea) using primers LR3 (Vilgalys
& Hester 1990) and LR0R (Vilgalys, unpubl.) in addition to
5.8SR and LR6 also used in the prior PCR amplication.
Geneious Pro v. 5 (Drummond et al. 2010) was used for
assembly of chromatograms and for multiple alignments
using the MAFFT plugin (Katoh et al. 2002) with manual
editing and optimisation of obtained alignments performed
when necessary. Ambiguously aligned parts were identied
by visual inspection of the alignments in Geneious and
excluded from the analyses using an Exclude statement
when running MrBayes. Unique sequences were deposited
in GenBank (Table 1).
Phylogenetic analyses
The aligned matrices were subjected to Bayesian analyses
using MrBayes v. 3.2 (Ronquist & Huelsenbeck 2003).
To identify the most suitable substitution model for the
Bayesian analyses, we used MrModeltest v. 2.3 (Nylander
2004), utilizing the Akaike Information Criterion. The analysis
was performed with two sets of four chains (one cold and
three heated) and the Stoprule option, stopping the analyses

Xerochrysium gen. nov. and Bettsia
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volume 4 · no. 2
Table 1. List of Chrysosporium and related species examined.
Strain1Species Notes1,2 Origin GenBank No.
CBS 593.71 Amauroascus aureus Clade IV Decayed wood, Cryptomeria japonica, Mt. Yudono,
Japan KC989708
Neotype of Gymnoascus aureus
CBS 342.64 Aphanoascus terreus Clade II (no living ex-type
culture available) Lawn soil, India. Anamorph, C. indicum (H.S.
Randhawa & R.S. Sandhu) Garg KC989709
CBS 272.66 Arthroderma ciferrii
(Isotype) Clade VII Soil, Arkansas, USA. Anamorph, C. georgiae
(Varsavsky & Ajello) Oorschot KC989711
CBS 473.77 Arthroderma tuberculatum
(Type) Clade VII Feather of Turdus americanus, Urbana, IL, USA KC989710
FRR 4958 C. botryoides (Type3) = CBS 492.91 Nest of Osmia cornifrons, Nagano region, Japan KC989712
CBS 643.79 C. carmichaelii (Type) Clade VI Michigan, USA KC989713
CBS 688.71 Bettsia alvei (Type) Pollen in honeycomb, Zeeland, Denmark KC989714
FRR 2000 C. farinicola = UAMH 4688 Prunes, Young, NSW, Australia KC989715
CBS 298.95 C. farinicola Prune processing equipment, UK KC989716
FRR 77 C. fastidium (Type) = IMI 126288, CBS 154.67,
ATCC 18053, ATCC 36783,
UAMH 2369
Dried prunes, Leeton, NSW, Australia KC989717
FRR 376 C. fastidium Dried prunes, Australia KC989718
FRR 81 C. fastidium Identied as C. fastidium,
appearance and LSU sequence
of C. farinicola (Table 3, Fig. 1)
Dried prunes, Australia KC989725
J211 C. fastidium Identied as C. fastidium,
appearance and LSU sequence
of C. farinicola (Table 3, Fig. 1)
Dried prunes, Australia KC989734
FRR 4953 C. globiferum (Type) = CBS 454.91 Nest cells of Osmia cornifrons, Nagano region, Japan KC989719
FRR 4957 C. globiferum var.
articulatum (Type) = CBS 493.91 Nest cells of Osmia cornifrons, Nagano region, Japan KC989720
FRR 4956 Chrysosporium globiferum
var. niveum (Type) = CBS 455.91 Nest cells of Osmia cornifrons, Nagano region, Japan KC989721
FRR 4954 C. hispanicum (Type) = CBS 486.91 Nest cells of Osmia cornuta, Valladolid, Spain KC989722
FRR 4955 C. holmii (Type) = CBS 487.91 Nest cells of Osmia rufa, Glostrup, Denmark KC989723
FRR 2357 C. inops Chopped Chinese dates, Australia KC989724
CBS 297.95 C. inops Chinese ve spice powder, Shefeld, UK JF922024
FRR 4952 C. medium (Type) = CBS 488.91 Nest cells of Osmia rufa, Tåstrup, Denmark KC989726
FRR 4949 C. medium var.
spissescens (Type) = CBS 489.91 Nest cells of Osmia rufa, Tåstrup, Denmark KC989727
CBS 388.68 C. merdarium (Type species) Soil KC989728
FRR 4950 C. minus (Type) = CBS 490.91 Nest cells of Osmia rufa, Karlslunde, Denmark KC989729
FRR 4951 C. pyriforme (Type) = CBS 491.91 Nest cells of Osmia rufa, Sweden KC989730
CBS 634.79 C. sulfureum Clade VI Cheese rind, Switzerland KC989731
CBS 640.79 C. synchronum (Type) Clade VIII Sordariomycetes Commercially grown Agaricus bisporus, Edmonton,
Alberta, Canada KC989732
CBS 171.62 C tropicum (Isotype) Clade I Woollen overcoat, Guadalcanal, Solomon Is. KC989733
CBS 153.67 C. xerophilum = ATCC 18052, IMI 126287,
UAMH 2368
Dried prunes, Sydney, NSW, Australia JF922023
CBS 437.88 C. zonatum (Type) Clade I Horse dung, Kuwait KC989735
CBS 407.71 Nannizziopsis vriesii Clade IV Ameiva (lizard) skin and lung, Netherlands KC989736
Status: Isotype of Rollandina
vriesii
CBS 708.79 Renispora avissima Clade IV Soil in barn housing Myotis velifer, Kansas, USA KC989737
CBS 120.77 Uncinocarpus reesii (Type) Clade III Feather, Australia KC989738
1Culture collections of CBS (Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands), FRR (CSIRO Animal, Food and Health
Sciences, North Ryde, Australia); J (Dept of Microbiology, Swedish University of Agricultural Sciences, Uppsala, Sweden).
2Clade numbers refer to the groupings of Vidal et al. (2000).
3All types studies were ex-type cultures.

Pitt et al.
ARTICLE
232 ima fUNGUS
at an average standard deviation of split frequencies of 0.01.
The sample frequency was set to 100; the rst 25 % of trees
were removed as burn in.
Matrices and the resultant tree are available in TreeBASE,
as accession number 14206.
RESULTS
The striking result of the broadly based LSU analysis is that
the genus Chrysosporium as revived by Carmichael (1962)
and maintained by van Oorschot (1980) includes six clades
in three orders (Fig. 1). The type species of the genus is C.
corii, the correct name for which is C. merdarium, but no
cultures derived from the extant type material of these two
names could be located. The LSU sequence examined was
from CBS 388.68, derived from the type of C. merdarium
var. roseum. That occupied an isolated position in Leotiales
close to Geomyces pannorum and Pseudogymnoascus
roseus, well separated from other species. Vidal et al. (2000)
examined the ITS sequence from CBS 408.72, listed by
CBS as C. merdarium, but also stated to be derived from
the type of Gymnoascus uncinatus. Not surprisingly, that is
located in Onygenales. However, the epitypication of the
type species of Chrysosporium is beyond the scope of this
paper. The Chrysoporium spp. not isolated from dried foods
or bees were all incapable of growth on MY50G agar, and
again outside our scope.
Of immediate relevance, however, the LSU indicated
that the xerophilic species associated with food or bees are
also polyphyletic, belonging to two clades, one in Eurotiales,
where most xerophilic fungi belong, and the other in Leotiales.
Morphological and physiological characteristics support
this separation: the seven species in the Leotiales clade
viz. C. farinicola, C. fastidium, C. hispanicum, C. holmii,
C. medium, C. minor, and C. pyriformis, have a distinctly
different proportion of the conidial types characteristic of
the xerophilic Chrysosporium species, and generally have a
somewhat faster radial growth rate on MY50G-based media
at 20–30 °C than those species grouped in Eurotiales (C.
botryoides, C. globiferum, C. inops, and C. xerophilum;
Table 2). Species in the Leotiales clade did not grow at 37
°C, but had an optimum temperature around 25 °C; growth
rates at 0.89 aw and 20 °C were only somewhat slower than
at 25 °C and similar to those at 30 °C. Thus, this group
appears to be tolerant of cooler temperatures: in contrast,
species in the Eurotiales clade displayed a preference for
warmer temperatures with most rapid growth typically at
30 °C and slower growth at 20 °C. All species apart from
C. inops were capable of growth at 37 °C. In addition to a
broader temperature range, these species also showed a
somewhat greater tolerance of high and low water activities:
most species showed linear growth or at least germination
within the range 0.99–0.71 aw at 25–30°C. Such growth at
extremes of water activity was sporadically observed among
species in the Leotiales clade: within 50 d, germination, but
not linear growth, was noted at 0.73–0.71 aw for certain
species only and growth at 0.99 aw was only observed at 20
°C. Species from the two clades also differed greatly during
growth on Czapek Casein 50G agar (Table 3). Species
belonging to Eurotiales yielded dense, white, slightly
occose colonies with reverse colours in cream/pale apricot
to yellow/khaki, and colony diameters > 40 mm within 14
d (18 mm for C. inops); whereas, species within Leotiales
yielded sparse, hyaline colonies with little aerial mycelium,
8–26 mm diam.
The xerophilic species in the Leotiales clade include
C. farinicola, the asexual morph of Bettsia alvei. Based on
sequence identity and a striking number of physiological and
morphological similarities in the asexual morph, the xerophilic
species in the Leotiales clade, apart from C. fastidium, are
placed in synonymy, regardless of presence/absence of
sexual morph. Under the new Code (McNeill et al. 2012), the
strictly asexual Chrysosporium species in Leotiales should
be renamed in Bettsia, the oldest available generic name.
The correct epithet is B. alvei, as its basionym Pericystis alvei
dates from 1912, while the basionym of C. farinicola, Ovularia
farinicola, was introduced in 1928 (Skou 1975, van Oorschot
1980). Retention of C. fastidium as a separate species, B.
fastidia, is warranted based on the distinct yellow-brown
colours of the mycelium, somewhat slower growth rate on
MY50G, and its placement as a sister clade to B. alvei (Fig.
1).The xerophilic Chrysosporium species grouped together
in Eurotiales are all asexual morphs. In the absence of any
available name, the new generic name Xerochrysium is
given to them here. The LSU tree indicated that C. inops is
distinct, but other species were not separated satisfactorily
(Fig. 1). Based on similarities in morphology, physiology and
molecular data, the remaining species are synonymised
under the oldest name, C. xerophilum.
The genus most closely related to Xerochrysium is
Xeromyces (Fig. 1), which contains one species, the extreme
xerophile X. bisporus. Xeromyces is distinguished from
Xerochrysium because it is primarily a sexual genus, in which
fresh isolates readily produce characteristic asci containing
two D-shaped ascospores; unlike Xerochrysium, it does not
produce chlamydo- or aleurioconidia, instead producing a
rare Frasierella asexual morph.
TAXONOMY
Although molecular analyses have shown that species in
Bettsia and species now placed in the new genus Xerochrysium
are widely separated phylogenetically, striking similarities exist
in microscopic appearance. However, in culture these two
groups of species are not difcult to separate. Growth rates of
Bettsia species are faster than those of Xerochrysium species,
although some overlap exists (Table 3). The other major
distinguishing feature is the proportion of aleurioconidia to
chlamydoconidia and arthroconidia: Bettsia species produce
predominantly aleurioconidia whereas Xerochrysium species
produce predominantly chlamydoconidia and arthroconidia
(see Figs 2–5).
Bettsia
Bettsia is characterised by the formation of small black
cleistothecia with a distinctive three-celled appendage.
Asci are evanescent, and ascospores have smooth, dark

Xerochrysium gen. nov. and Bettsia
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233
volume 4 · no. 2
walls. The type and only species is a hyphomycete asexual
morph, with aerial hyphae bearing solitary aleurioconidia and
intercalary chlamydoconidia.
Skou (1972) erected the genus Bettsia as a new name for
Pericystis Betts 1912 (non Pericystis J. Agardh 1848). The
type species is B. alvei. Molecular analysis (LSU) indicates
that Bettsia lies in Leotiales, with a possible relationship to
the genus Pseudeurotium.
One other species with no known sexual morph is
accepted here: B. fastidia.
Chrysosporium fastidium FRR77 (T)
Chrysosporium fastidium FRR376
Xeromyces bisporus (T)
Thelebolus caninus
Rhytisma andromedae
Nanniziopsis vriesii
Pseudogymnoascu s roseu s
Chrysosporium synchronum (T)
Gymnoascus reesii (T)
Bettsia alvei CBS688.71 (T)
Chrysosporium pseudomerdarium UAMH3089
Peltigera degenii
Chrysosporium farinicola FRR 2000
Amauroascus aureus (T)
Neurospora crassa
Chrysosporium botryoides (T)
Chrysosporium xerophilum
Lecanora achariana
Pseudeurotium zonatum DQ470988 (T)
Erysiphe frie sii
Chrysosporium minor (T)
Marthamyces emarginatus
Chrysosporium farinicola CBS298.95
Byssochlamys nivea
Chrysosporium merdarium (T)
Roccellographa cretacea
Arthonia caesia
Pleospora herbarum (T)
Arthroderma ciferrii
Pseudeurotium sp. 795_3_CY02
Coccomyces leptideus
Chrysosporium hispanicum (T)
Sclerotinia sclerot iorum
Leiothe cium ellipsoideu m (T)
Chrysosporium holmii (T)
Penicillium glabrum
Monascus eremophilus (T)
Pyrenula cruenta
Chrysosporium medi um var. medium (T)
Golovinomyces orontii
Pseudeurotium sp. 795_2_CY02
Pseudeurotium sp. 799_1_P01
Chrysosporium inops CBS297.95
Lachnum virgineum
Hamigera avellanea (T)
Hemicarpenteles ornatus (T)
Leotia lubrica
Geomyces panno rum
Chrysosporium globiferum var. niveum (T)
Aspergillus restrictus (T)
Chrysosporium sulfureum
Paecilomyces variotii (T)
Chrysosporium inops FRR 2357
Chrysosporium pyriforme (T)
Chrysosporium pseudomerdarium
Art hroderma tuberculat um (T)
Malbranchea cinnam omea
Euro tiu m herbariorum ( T)
Leuconeurospora pulcherrima
Aspergillus candidus (T)
Pseudonectria rousseliana
Pseuderotium zonatum AF096198 ( T)
Sordaria macrospora
Petriella setifera
Aspergillus penicillioides (T)
Sphinctrina turbinata
Monascus lunisporas
Oidiodendron fuscum (T )
Chrysosporium globiferum var. globiferum (T)
Eurotium amstelodami (T)
Cordyceps kyushuensis
Crinula caliciformis
Xyla ria hypoxylon
Bulgaria inquinans
Chrysosporium tropicum
Chrysosporium fastidium J211*
Oidium citri
Chrysosporium zonatum (T )
Chrysosporium carmichaelii (T)
Geoglossum nigritum
Capronia pilosella
Pseudeurotium sp. 797_2_CY01
Gyromitra melaleucoides
Coryn ascus sepedonium
Verrucaria pachyderma
Chrysosporium medium var. spissescens
Pezicula carpinea
Eupenicillium osmophilum (T)
Uncinocarpus reesii (T)
Penicillium chrysogenum (T)
Aphanoascus terreus
Connersia rilstonii
Amorphotheca resinae
Mycocalicium polyporaeum
Monascus ruber (T)
Magnaporthe grisea
Aleuria aurantia
Chrysosporium globiferum var. articulatum (T)
Hyphozyma variabilis (T)
Warcupiella spinulosa (T)
Chrysposporium fastidium FRR81*
Therm oascu s crus taceus ( T)
Dothidea sambuci (T)
1
0. 92
0.6
0. 75
0. 83
1
0. 99
0. 98
1
0.9
1
1
0. 99
1
0. 81
1
0. 96
1
1
1
0. 86
0. 99
0. 61
0. 95
1
1
0. 67
0.8
1
0. 85
0. 83
0. 83
1
0. 77
1
0.8
1
1
1
1
0. 98
0. 93
1
0. 99
0. 99
0. 68
0. 99
1
1
1
0. 98
1
0. 78
0. 74
0. 76
1
0.6
0. 79
0. 91
1
1
0. 72
0. 98
1
0. 85
0.9
0. 98
1
1
1
1
0. 97
0. 59
1
0. 82
0. 94
0. 99
0. 99 1
0. 62
1
0. 96
0. 94
1
1
1
0. 97
Leotiomycetes
Sordariomycetes
Leotiomycetes
Eurotiomycetes
Arthoniomycetes
Dothideomycetes
Lecanoromycetes
Geoglossomycetes
Pezizomycetes
Dothideomycetes
Bettsia
Xerochrysium
Fig. 1. Phylogeny based on 28S sequences of Chrysosporium species including xerophilic species isolated from foods or bee pollen. Classication
according to Lumbsch & Huhndorf (2010) in brackets. Leotiomycetes is supported in two clades and includes taxa noted by to have uncertain
taxonomic afnity. Two strains, J211 and FRR 81, were originally identied as C. fastidium, but upon examination their morphology was that of
C. farinicola.

Pitt et al.
ARTICLE
234 ima fUNGUS
Table 2. Radial growth rate (mm/d) of xerophilic Chrysosporium species on malt yeast media with water activity adjusted with glucose or a mixture of glucose and fructose at 37, 30, 25 and 20 °C.
Temp awB. alvei C. farinicola C. hispanicum C. holmii C. medium C. minus C. pyriforme C. fastidium C. xerophilum C. botryoides C. globiferum C. inops
CBS688.71, T1FRR2000 FRR4954, T FRR4955, T FRR4952 FRR4950 FRR4951 FRR77, T CBS153.67 FRR4958, T FRR4953, T CBS297.95
37 °C 0.99 ng2ng ng ng ng ng ng ng ng ng ng ng
0.89 ng ng ng ng ng ng ng ng 1.79±0.0830.80±0.22 1.12±0.06 ng
0.78 ng ng ng ng ng ng ng ng 0.39±0.10 0.39 0.38±0.05 ng
0.73 ng ng ng ng ng ng ng ng 0.14±0.02 germ4germ ng
0.71 ng ng ng ng ng ng ng ng 0.13±0.01 ng germ ng
30 °C 0.99 ng ng ng ng ng ng ng ng 0.90±0.11 germ 0.44±0.16 0.07±0.02
0.89 0.81±0.01 2.41±0.13 2.18±0.03 2.31±0.09 1.66±0.09 1.08±0.02 2.12±0.17 0.85±0.12 1.40±0.09 0.96±0.02 1.22±0.06 0.69±0.01
0.78 0.27±0.03 0.41±0.24 0.28±0.06 0.18±0.02 0.33±0.15 0.16±0.09 0.33±0.20 0.34±0.03 0.35±0.05 0.38±0.06 0.36±0.02 0.23±0.06
0.73 ng ng ng ng ng ng ng germ 0.24±0.05 0.14±0.01 0.15±0.01 0.08±0.01
0.71 ng ng ng ng ng ng ng ng 0.20±0.02 0.13±0.00 0.14±0.01 germ
25 °C 0.99 ng 0.10±0.02 0.05±0.01 0.11±0.02 ng ng ng ng 0.61±0.12 0.10±0.01 0.28±0.07 0.26±0.09
0.89 2.01±0.06 2.84±0.35 2.64±0.05 2.81±0.28 2.13±0.18 2.56±0.30 2.75±0.43 1.66±0.01 0.90±0.09 0.74±0.02 0.83±0.02 0.66±0.02
0.78 0.82±0.02 0.46±0.15 0.29±0.02 0.24±0.01 0.50±0.13 germ 0.21±0.01 0.57±0.03 0.29±0.01 0.30±0.04 0.30±0.05 0.18±0.01
0.73 ng germ germ ng ng ng germ 0.13±0.00 0.20±0.00 germ 0.12±0.01 0.11±0.04
0.71 ng ng germ ng ng ng germ germ 0.13±0.01 germ 0.09±0.01 germ
20 °C 0.99 0.10±0.02 0.59±0.34 0.50±0.37 0.50±0.26 0.48±0.14 0.17±0.01 0.36±0.28 0.09±0.03 0.55±0.13 0.08±0.00 0.17±0.09 0.21±0.02
0.89 1.96±0.01 2.10±0.37 1.96±0.18 2.34±0.15 1.91±0.10 1.69±0.34 2.04±0.32 1.47±0.02 0.58±0.08 0.50±0.02 0.54±0.07 0.41±0.03
0.78 0.54±0.05 germ germ ng ng ng 0.27±0.07 0.54±0.02 0.24 0.18±0.01 0.17±0.03 0.19±0.13
0.73 ng ng ng ng ng ng ng 0.13±0.01 0.10±0.01 germ germ germ
0.71 ng ng ng ng ng ng ng germ ng germ germ ng
Proposed
taxonomy Bettsia alvei Bettsia fastidia Xerochrysium xerophilum X. dermatitidis
1Ex-type culture.
2No growth observed within 50 d.
3Standard deviation of three replicates.
4Germination and micro-colony formation within 50 d.

Xerochrysium gen. nov. and Bettsia
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235
volume 4 · no. 2
Bettsia alvei (Betts) Skou, Friesia 10: 7 (1972).
(Fig. 2)
Basionym: Pericystis alvei Betts, Ann. Botan. 26: 795 (1912).
Synonyms: Ascosphaera alvei (Betts) Olive & Spiltoir,
Mycologia 47: 243 (1955).
Ovularia farinicola Burnside, Michigan Acad. Sci., Arts Lett.
8: 59 (1928).
Chrysosporium farinicola (Burnside) Skou, Friesia 11: 70
(1972).
Chrysosporium hispanicum Skou, Mycotaxon 43: 244 (1992).
Chrysosporium holmii Skou, Mycotaxon 43: 243 (1992).
Chrysosporium medium Skou, Mycotaxon 43: 248 (1992).
Chrysosporium medium var. spissescens Skou, Mycotaxon
43: 249 (1992).
Chrysosporium minus Skou, Mycotaxon 43: 250 (1992); as
“minor”.
Chrysosporium pyriforme Skou, Mycotaxon 43: 246 (1992);
as “pyriformis”.
Description: No growth on CYA at 5, 25 or 37 °C or on MEA
at 25 °C. Colonies on G25N 1–20 mm diam, of low, white
mycelium, or if the sexual morph is present, centrally grey from
the production of immature cleistothecia; margins mbriate;
reverse pale, but grey centrally if the sexual morph is produced.
Colonies on MY50G growing relatively rapidly at 7 d, 15–35
mm diam, low, plane, persistently white, or showing sectors
becoming translucent or greyish if the sexual morph is present,
reverse pale beneath white areas, but darker beneath grey
sectors; at 14 d, 40–65 mm diam, colonies remaining white if
only the asexual morph is present, but dark grey to black in the
presence of the sexual morph; reverse pale or dark.
Reproduction on MY50G predominantly solitary aleurio-
conidia. Fertile hyphae remain mostly undifferentiated and
dissolve in age. In isolates producing the sexual morph
areas or sectors of translucent growth develop on MY50G.
At maturity such areas become grey and then black as small
cleistothecia form. Cleistothecia formed on MY50G at 25 °C,
dark brown to black, usually maturing only after several weeks
at 15–25 °C, 25–60 μm diam, with walls thin and smooth, and
without internal structure; initials a row of three short cells,
12–18 x 6–8 μm overall, adhering to the cleistothecial wall
as a distinctive appendage; ascospores not liberated readily,
spherical, 5–6 μm diam, with dark walls, smooth to minutely
roughened.
Type: Denmark: Zeeland: Ringsted, Skee, a lyophilised
culture, from pollen in honeycomb, 1971, J. P. Skou (CBS
688.71 – neotype designated by Skou 1972; IMI 160840 –
ex-neotype culture).
Distinctive features: Bettsia alvei is distinguished from B.
fastidia by persistently white growth in the absence of the
sexual morph. In addition, while only some isolates of B. alvei
produce the sexual morph, no sexual morph is known for B.
fastidia.
Physiology: Optimal growth at approx. 0.89 aw and 25 °C.
No growth at 37 °C, good growth at 20 °C. Growth at 0.99 aw
observed at 20 °C only; minimum aw estimated to be approx.
0.70–0.73 based on germination of certain strains at 0.71 aw.
Ecology: Bettsia alvei, often under the name Chrysosporium
farinicola, has been isolated from a range of low water
activity substrates, including honeycomb, prunes and prune
processing equipment, sultanas, mixed dried fruit, chocolate,
jelly crystals and coconut from Australia, the United Kingdom,
Sri Lanka, Czechoslovakia and Denmark (Pitt & Hocking
2009).
References: Skou (1975), and van Oorschot (1980).
Fig. 2. Bettsia alvei . A. Colonies of a strictly asexual
strain, FRR 2000, on MY50G, after 14 d at 25 °C. B.
Colonies of a sexually reproducing strain, FRR 380,
on MY50G, after 14 d at 25 °C. C. Aleurioconidia.
D. FRR 380, mature cleistothecia containing
ascospores. E. Ascospores. Bars: C = 10 µm, D = 25
µm, and E = 5 µm.

Pitt et al.
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236 ima fUNGUS
Bettsia fastidia (Pitt) Pitt, comb. nov.
MycoBank MB806122
(Fig. 3)
Basionym: Chrysosporium fastidium Pitt, Trans. Br. mycol.
Soc. 49: 467 (1966).
Description: No growth on CYA at 5, 25 or 37 °C, or on
MEA. Colonies on G25N 1–5 mm diam, of low, dense, white
mycelium. Colonies on MY50G at 7 d 15–22 mm diam, low,
plane and sparse, pale yellow or brown, reverse yellow
brown; at 14 d, 35–42 mm diam, low and plane, margins
sparse and mbriate, white, centres more dense, dull yellow;
reverse yellow to pale brown.
Reproduction on MY50G predominantly by smooth
walled aleurioconidia borne singly on short pedicels or less
commonly sessile, spheroidal (oblate or prolate) to broadly
ellipsoidal, 6–9 × 5–8 μm, in age released by dissolution
of the pedicels; terminal chlamydoconidia, spherical to
pyriform or pedunculate, 8–12 × 6–10 μm, also produced,
but intercalary chlamydoconidia and arthroconidia rare. No
sexual morph known.
Type: Australia: New South Wales: a dried Petri dish culture,
from dried prunes, 1964, J. I. Pitt (UAMH 2368 – holotype;
FRR 77, CBS 154.67, ATCC 18053, ATCC 36783, and IMI
126288 – ex-holotype cultures).
Distinctive features: Bettsia fastidia forms dull yellow to
yellow-brown colonies; conidia produced on G25N or
MY50G are predominantly aleurioconidia with few intercalary
chlamydoconidia or arthroconidia. This species is readily
distinguished from B. alvei, as the latter species show no
yellow or brown colouration, and by slower growth than B.
alvei on MY50G.
Taxonomy: Van Oorschot (1980) considered C. fastidium a
synonym of C. farinicola. However, our examination of the
strain she examined, FRR 77 (CBS 154.67), showed that that
culture was incorrectly labelled. The two species are readily
distinguished by colony colour and by LSU sequence.
Physiology: A mesophilic obligate xerophile, B. fastidia has
a minimum for growth of 0.69 aw (Pitt & Christian 1968), and
displays optimal growth at approx. 0.89 aw and 25 °C. No
growth at 37 °C, good growth at 20 °C. Growth at 0.99 aw
observed at 20 °C only.
Ecology: This species has been repeatedly isolated from
prunes (dried and high moisture) and prune processing
machinery in New South Wales, Australia. There are no
records of isolation from other substrates or other countries,
indicating that this is a rare species with a restricted habitat.
Xerochrysium Pitt, gen. nov.
MycoBank MB807003
Type species: Xerochrysium dermatitidis (A. Agostini) Pitt
2013 (syn. Glenosporella dermatitidis A. Agostini 1930).
Description: Xerochrysium is a genus of Eurotiales known
only as asexual morphs which is erected to accommodate
xerophilic species formerly placed in Chrysosporium. The
known species grow poorly, if at all, on standard media
including CYA, MEA and potato dextrose agar. Growth
is slow on G25N. Optimal growth is obtained on MY50G,
with a water activity below 0.9. Microscopically species are
characterised by the production of aleurioconidia, but also
by the formation of chlamydoconidia and arthroconidia,
such that mature colonies are often made up predominantly
Table 3. Distinguishing features of species in Bettsia and Xerochrysium.
Species CYA, MEA G25N (mm) Colony size (mm) and
morphology on MY50G Dominant microscopic
morphology from MY50G Colony size (mm) and
morphology on CZC50G
Bettsia alvei No growth 1–20 (7 d) 15–35 (7 d);
40–65 (14 d) Solitary aleurioconidia 8–26 mm (14 d)
Colonies persistently
white with a pale reverse;
or black with a black
reverse in the presence of
cleistothecia
Sparse, hyaline
B. fastidia No growth 1–5 (7 d) 15–22 (7 d); Solitary aleurioconidia 21–26 mm (14 d)
35–42 (14 d) Sparse, hyaline
Colonies dull yellow to
yellow brown; reverse
yellow brown
Xerochrysium
dermatitidis No growth - 3 mm 1–9 (7 d) 4–10 (7 d); Chlamydo- and
arthroconidia 18 mm (14 d)
12–20 (14 d) Dense, white, slightly occose,
reverse cream-yellow reverse,
occasionally red (Kinderlerer 1995)White or translucent
X. xerophilum No growth - 3 mm 1–9 (7 d) 9–20 (7 d); Chlamydo- and
arthroconidia 40–43 mm (14 d)
20–38 (14 d) Dense, white, slightly occose,
reverse cream-yellow to khaki-
yellow
White; reverse white or pale
yellow to apricot, khaki

Xerochrysium gen. nov. and Bettsia
ARTICLE
237
volume 4 · no. 2
of these spore types, with little undifferentiated mycelium
evident.
Two species are accepted here: X. dermatitidis and X.
xerophilum.
Xerochrysium dermatitidis (A. Agostini) Pitt, comb.
nov.
MycoBank MB807005
(Fig. 4)
Basionym: Glenosporella dermatitidis A. Agostini, Atti Ist. Bot.
Univ. Pavia 2: 93 (1930).
Synonym: Chrysosporium inops J.W. Carmich., Can. J. Bot.
40: 1156 (1962).
Description: After 7 d at 25 °C, colonies on CYA and MEA
absent or up to 3 mm diam. Colonies on G25N 1–9 mm
diam, varying from low and translucent to deep and occose,
white; reverse pale to amber or duller yellow brown. No
growth on CYA at 5 or 37 °C. Colonies on MY50G at 7 d,
4–10 mm diam, at 14 d, 12–20 mm diam, varying from low,
sparse and translucent to moderately deep, dense and with a
occose surface, white or if translucent, uncoloured; reverse
uncoloured to pale yellow brown.
Reproductive structures on G25N or MY50G at 7 d primarily
short chains of chlamydoconidia and arthroconidia, borne by
retrogressive differentiation from hyphal tips and as intercalary
chains; some terminal chlamydoconidia also present; at
maturity on MY50G (2–4 wk), clusters of chlamydoconidia
and arthroconidia also present, formed by retrogressive
differentiation of groups of short branching hyphae with a lateral
stipe as their common origin. Chlamydoconidia spherical,
4–7(–10) μm diam; arthroconidia cylindroidal or doliiform (barrel
shaped), 3–8 × 3–6 μm, those of greater width intergrading
with chlamydoconidia; aleurioconidia uncommon, ellipsoidal to
pyriform, 5–8 μm diam or longer. Large chlamydoconidia, up
to 25 μm diam, with walls up to 2 μm thick, produced by some
isolates. Sexual morph unknown.
Type: Italy: Pavia: Pavia, lyophilised culture obtained from
human skin, 1930, A. Agostini ( CBS 132.31 – lectotype
designated here; IMI 96729, UAMH 802, and FRR 2376 –
ex-lectotype cultures).
Nomenclature: Based on CBS 132.31, received as
Glenosporella dermatitidis, Carmichael (1962) transferred this
species to Chrysosporium. However, as he had already used
the epithet “dermatitidis” in C. dermatitidis, he transferred G.
dermatitidis as C. inops nom. nov. On transfer to the new
genus Xerochrysium, this epithet is again available, so the
new combination is correctly X. dermatitidis.
Distinctive features: In culture, Xerochrysium dermatitidis
and X. xerophilum are very similar: X. dermatitidis grows
more slowly on standard media and on CZC50G (Table 3).
In young colonies (7 d), terminal chlamydoconidia are often
the dominant conidium type in X. dermatitidis. Aleurioconidia
are rare.
Physiology: Van Oorschot (1980) reported that this species had
a minimum growth temperature of 20 °C, an optimum of 25 °C,
and a maximum of 30 °C. However, her data were obtained on
media of very high aw, and limits are undoubtedly wider under
optimal conditions. No growth at 37 °C, and maximum growth
at approx. 0.88 aw and 25 °C (Leong et al. 2011). Maximum aw
for growth is 0.99 and minimum aw < 0.71, as germination was
observed at 0.71 aw and 30 °C (Table 2). It is clear, contrary to
Fig. 3. Bettsia fastidia (FRR
77). A–B. Obverse and reverse
of colonies on MY50G, after 14
d at 25 °C. C–D. Aleurioconidia
borne on pedicels. Bars = 10
µm.

Pitt et al.
ARTICLE
238 ima fUNGUS
previous reports (Pitt & Christian 1968, van Oorschot 1980),
that X. dermatitidis is an extreme xerophile.
Ecology: As noted by de Hoog et al. (2000), X. dermatitidis
is not a dermatophyte, but a xerophile. With the exception of
the original isolation by Agostini (1930) from human skin, all
isolates known have come from dried or concentrated foods.
Sources have included spice powders, chopped dates,
gelatine confections, chocolate and nuts (Pitt & Hocking
2009).
Xerochrysium xerophilum (Pitt) Pitt, comb. nov.
MycoBank MB807006
(Fig. 5)
Basionym: Chrysosporium xerophilum Pitt, Trans. Br. mycol.
Soc. 49: 468 (1966).
Synonyms: Chrysosporium botryoides Skou, Mycotaxon 43:
252 (1992).
Chrysosporium globiferum Skou, Mycotaxon 43: 253 (1992).
Chrysosporium globiferum var. articulatum Skou, Mycotaxon
43: 254 (1992).
Chrysosporium globiferum var. niveum Skou, Mycotaxon 43:
255 (1992).
Description: After 7 d at 25 °C, colonies on CYA and
MEA absent or up to 3 mm diam. Colonies on G25N 1–9
mm diam, varying from low and translucent to deep and
occose, white; reverse pale. No growth on CYA at 5 or 37
°C. Colonies on MY50G at 7 d 9–20 mm diam, at 14 d, 20–
38 mm diam, varying from low, sparse and translucent to
moderately deep, dense and with a occose surface, white
or if translucent, uncoloured; reverse uncoloured to yellow-
apricot, khaki.
Vegetative hyphae rare in mature colonies on G25N
or MY50G, having transformed into chlamydoconidia and
arthroconidia; chlamydoconidia spherical, 6–9 µm diam,
arthroconidia 4–5 × 3–9 µm (width sometimes exceeding
length), the two spore types intergrading. Aleurioconidia
borne on hyphal tips or laterally on short pedicels, often
subsequently tranformed into arthroconidia as well,
cylindroidal or doliiform. Terminal conidia 10–11 µm diam, on
pedicels smaller, ellipsoidal to pyriform, 5–7 × 7–8 µm.
Type: Australia: New South Wales: Sydney, a dried Petri
dish culture, from spoiled high moisture prunes, 1962, J.I.
Pitt (UAMH 2368 – holotype; CBS 153.67, FRR 503, ATCC
18053, and IMI 126287 – ex-holotype cultures).
Distinctive features: Xerochrysium xerophilum grows
more rapidly than X. dermatitidis (Table 3). In addition,
Xerochrysium xerophilum produces higher numbers of
aleurioconidia and at maturity, is distinguished by the almost
complete differentiation of vegetative hyphae into intercalary
chlamydoconidia and arthroconidia; even aleurioconidium
pedicels often becoming thick-walled spores.
Taxonomy: Based on a morphological study, Boekhout et
al. (1989) concluded that Chrysosporium xerophilum was
a synonym of Sporotrichum pruinosum. However, as they
reported that their strain grew well on such high water activity
media as 2 % MEA and phytone yeast extract agar, and that
its optimal growth temperature was 36–39 °C, completely at
odds with the original description (Pitt 1965), it is clear that
the strain they studied was incorrectly identied.
Physiology: Xerochrysium xerophilum grows over a broad
range of aw, with maximum and minimum aw for growth of
Fig. 4. Xerochrysium dermatitidis (FRR 2353). A. Colonies on MY50G, after 14 d at 25 °C. B–D. Chains of arthroconidia borne by hyphal
transformation. Bars: B–C = 10 µm, D = 20 µm.

Xerochrysium gen. nov. and Bettsia
ARTICLE
239
volume 4 · no. 2
approx. 0.99 and 0.66, respectively, and optimum around
0.94 (Table 2, Leong et al. 2011). Optimum temperature for
growth is 30–37 °C, and growth occurs at 20 °C.
Ecology: Originally isolated from prunes, X. xerophilum has
also been found in maize stored for long periods, chocolate
and coconut (Pitt & Hocking 2009).
DISCUSSION
The result of the broadly based LSU analysis, that
Chrysosporium as currently circumscribed includes six
clades in three orders, is perhaps not surprising, as the basic
asexual morph structure on which the genus is based, the
aleurioconidium, is a simple conidial form that could readily
have arisen more than once. More surprising is that the
xerophilic species belong to two clades, in radically different
orders. For a long time it was believed that xerophily, a highly
evolved characteristic involving the many genes required to
synthesise and retain small molecules such as glycerol, and
operate all cellular processes in a more or less thick syrup,
had arisen only once, and that all xerophilic species could be
found in Eurotiales (or ascomycetous yeasts from a lineage
close to Eurotiales). A very small number of exceptions have
been identied in relatively recent years: Trichosporonoides
nigrescens (Hocking & Pitt 1981) produces clamp
connections, indicating a basidiomycetous afnity, while
the isolated genus Wallemia has also been shown to be a
basidiomycete by molecular methods and microscopy (Zalar
et al. 2005, Padamsee et al. 2012). However, no species
in Leotiales has previously been shown to have xerophilic
properties.
The ecology of these species is also of interest.
Carmichael (1962) described the rst xerophilic species to
be placed in Chrysosporium, C. inops, from concentrated
orange juice, and C. xerophilum and C. fastidium were
described from prunes (dried plums) soon afterwards
(Pitt 1966). When recombining Ovularia farinicola into
Chrysosporium, Skou (1975) drew attention to the main
natural source of these fungi, beehives, bee pollen and
honey. At the same time, it is clear that some of these
species are also common food spoilage fungi: Xerochrysium
dermatitidis (as C. inops), X. xerophilum, and B. alvei have
been repeatedly isolated from concentrated or dried foods.
Bettsia alvei has been recorded from honeycomb, prunes
and processing equipment, dried vine fruits, chocolate,
and copra, from several widely separated countries, and
X. dermatitidis and X. xerophilum are also known to be
widespread in similar types of products, sometimes causing
spoilage. Although repeatedly isolated in Australia from
prunes and prune processing equipment, B. fastidia has not
been found elsewhere (Pitt & Hocking 2009). Despite the
narrow ecological niche of B. fastidia, all of these species,
as well as the extreme xerophile Xeromyces bisporus,
are associated with food or feed, and require highly
concentrated media such as MY50G for effective isolation
(Pitt & Hocking 2009). As their colonies on this medium are
somewhat similar in appearance, being pale to white and
low, a common key to species in these three genera is given
below.
Fig. 5. Xerochrysium xerophilum (FRR 503). A. Colonies on MY50G, after 14 d at 25 °C. B–C. Chains of arthroconidia borne by hyphal
transformation. Bars = 10 µm.

Pitt et al.
ARTICLE
240 ima fUNGUS
Key to xerophilic fungi in the genera Bettsia, Xerochrysium, and Xeromyces
1 Colonies on MY50G producing D-shaped ascospores in pairs ....................................................... Xeromyces bisporus
Colonies on MY50G not producing D-shaped ascospores; instead aleurioconidia and/or chlamydoconidia observed .... 2
2 (1) Colonies on MY50G 35–65 mm after 14 d at 25 °C; colony and reverse white, yellow-brown, or black;
aleurioconidia abundant, chlamydoconidia rare. No growth at 37 °C. Growth on CZC50G poor, yielding sparse,
hyaline colonies ........................................................................................................................................................ 3
Colonies on MY50G 12–38 mm after 14 d at 25 °C; colony and reverse white; chlamydoconidia and/or
arthroconidia abundant, aleurioconidia occasionally present. Growth at 37 °C present or absent.
Colonies on CZC50G dense, white; reverse in yellow-khaki shades, occasionally red ............................................ 4
3 (2) Colonies on MY50G 40–65 mm after 14 d, white or black, reverse pale or black ........................................ Bettsia alvei
Colonies on MY50G 35–42 mm after 14 d, pale yellow or brown with a yellow brown reverse ................ Bettsia fastidia
4 (2) Growth on MY50G typically 15 mm or less after 14 d (up to 20 mm); no growth at 37 °C .... Xerochrysium dermatitidis
Growth on MY50G 20–38 mm after 14 d; growth at 37 °C .................................................... Xerochrysium xerophilum
ACKNOWLEDGEMENTS
This research was supported by the Faculty of Science and
Agriculture, Swedish University of Agricultural Sciences, the Carl-
Tryggers Foundation (grant CTS 09: 347), and FORMAS (The
Swedish Research Council for Environment, Agricultural Sciences
and Spatial Planning, grant 2010-1470). We thank Ellinor Andersson
for technical assistance, Robert A. Samson for generously providing
some cultures, and he and Johan Schnürer for fruitful discussions.
We are also grateful for sequences made available in the AFTOL
project (Assembling the Fungal Tree of Life).
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