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Delimiting Cladosporium from morphologically similar genera

¹ CBS Fungal Biodiversity Centre, P.O. Box 85167, 3508 AD Utrecht, The Netherlands
² Martin-Luther-Universität, Institut für Biologie, Geobotanik und Botanischer Garten, Herbarium, Neuwerk 21, D-06099 Halle (Saale), Germany
³ Botanische Staatssammlung München, Menzinger Straße 67, D-80638 München, Germany

^* Correspondence: Pedro Crous, p.crous{at}cbs.knaw.nl

	Abstract

TOP Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
The genus Cladosporium is restricted to dematiaceous hyphomycetes with a coronate scar type, and Davidiella teleomorphs. In the present study numerous cladosporium-like taxa are treated, and allocated to different genera based on their morphology and DNA phylogeny derived from the LSU nrRNA gene. Several species are introduced in new genera such as Hyalodendriella, Ochrocladosporium, Rachicladosporium, Rhizocladosporium, Toxicocladosporium and Verrucocladosporium. A further new taxon is described in Devriesia (Teratosphaeriaceae). Furthermore, Cladosporium castellanii, the etiological agent of tinea nigra in humans, is confirmed as synonym of Stenella araguata, while the type species of Stenella is shown to be linked to the Teratosphaeriaceae (Capnodiales), and not the Mycosphaerellaceae as formerly presumed.

Taxonomic novelties: Devriesia americana Crous & Dugan, sp. nov., Hyalodendriella Crous, gen. nov., Hyalodendriella betulae Crous sp. nov., Ochrocladosporium Crous & U. Braun, gen. nov., Ochrocladosporium elatum (Harz) Crous & U. Braun, comb. nov., Ochrocladosporium frigidarii Crous & U. Braun, sp. nov., Rachicladosporium Crous, U. Braun & Hill, gen. nov., Rachicladosporium luculiae Crous, U. Braun & Hill, sp. nov., Rhizocladosporium Crous & U. Braun, gen. nov., Rhizocladosporium argillaceum (Minoura) Crous & U. Braun, comb. nov., Toxicocladosporium Crous & U. Braun, gen. nov., Toxicocladosporium irritans Crous & U. Braun, sp. nov., Verrucocladosporium K. Schub., Aptroot & Crous, gen. nov., Verrucocladosporium dirinae K. Schub., Aptroot & Crous, sp. nov.

Keywords Cladosporium / Davidiella / food spoilage / hyphomycetes / indoor air / LSU phylogeny / taxonomy

	INTRODUCTION

TOP Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
Cladosporioid hyphomycetes are common, widespread fungi. The genus Cladosporium Link is based on the type species, Cladosporium herbarum (Pers.: Fr.) Link, which in turn has been linked to Davidiella Crous & U. Braun teleomorphs (Braun et al. 2003, Schubert et al. 2007b - this volume). Cladosporium is one of the largest, most heterogeneous genera of hyphomycetes, comprising more than 772 names (Dugan et al. 2004), and including endophytic, fungicolous, human pathogenic, phytopathogenic and saprobic species. Species of this genus affect daily human life in various ways. The common saprobic members of Cladosporium occur on all kinds of senescing and dead leaves and stems of herbaceous and woody plants, as secondary invaders on necrotic leaf lesions caused by other fungi, are frequently isolated from air, soil, food stuffs, paint, textiles and other organic matters, are also known to be common endophytes (Riesen & Sieber 1985, Brown et al. 1998, El-Morsy 2000) as well as phylloplane fungi (Islam & Hasin 2000, De Jager et al. 2001, Inacio et al. 2002, Stohr & Dighton 2004, Levetin & Dorsey 2006). Furthermore, some Cladosporium species are known to be potential agents of medical relevance. Cladosporium herbarum is, for instance, a common contaminant in clinical laboratories and causes allergic lung mycoses (de Hoog et al. 2000, Schubert et al. 2007b - this volume).

In spite of the enormous relevance of this genus, there is no comprehensive modern revision of Cladosporium, but some attempts to revise and monograph parts of it have been initiated during the last decade (David 1997, Partridge & Morgan-Jones 2002, Wirsel et al. 2002, Braun et al. 2003, Dugan et al. 2004, Park et al. 2004, Seifert et al. 2004, Schubert & Braun 2004, 2005a, b, 2007, Heuchert et al. 2005, Schubert 2005a, b, Schubert et al. 2006).

Previous molecular studies employing rDNA ITS sequence data (Crous et al. 2001) have shown Cladosporium spp. to cluster adjacent to the main monophyletic Mycosphaerella Johanson cluster, suggesting a position apart from the latter genus. Braun et al. (2003) carried out more comprehensive sequence analyses, based on ITS (ITS-1, 5.8S and ITS-2) and 18S rDNA data, providing further evidence that Cladosporium s. str. represents a sister clade of Mycosphaerella.

Various authors discussed the taxonomy and circumscription of Cladosporium (von Arx 1981, 1983, McKemy & Morgan-Jones 1990, Braun 1995), reaching different conclusions. However, a first decisive revision of Cladosporium, leading to a more natural concept of this genus, was published by David (1997), who carried out comprehensive scanning electron microscopic examinations of the scar and hilum structure in Cladosporium and Heterosporium Klotzsch ex Cook. The first Scanning Electron Micrograph (SEM) studies of these structures, published by Roquebert (1981), indicated that the conidiogenous loci and conidial hila in Cladosporium are characterised by having a unique structure. David (1997) confirmed these observations, based on a wide range of Cladosporium and Heterosporium species, and demonstrated that the structures of the conidiogenous loci and hila in the latter genus fully agree with those of Cladosporium, proving that Heterosporium was indeed a synonym of Cladosporium s. str. He introduced the term "coronate" for the Cladosporium scar type, which is characterised by having a central convex part (dome), surrounded by a raised periclinal rim (David 1997), and showed that this type is confined to anamorphs, as far as experimentally proven, connected with teleomorphs belonging in "Mycosphaerella" s. lat. These results were confirmed in a later phylogenetic study by Braun et al. (2003). Cladosporium s. str. was shown to be a sister clade to Mycosphaerella s. str., for which the new teleomorph genus Davidiella was proposed. Although no clear morphological differences were reported between Davidiella and Mycosphaerella, a further study by Aptroot (2006) found ascospores of Davidiella to have characteristic irregular cellular inclusions (lumina), which are absent in species of Mycosphaerella, along with periphysoids and pseudoparaphyses (Schubert et al. 2007b - this volume). Furthermore, a higher order phylogeny study by Schoch et al. (2006), which employed DNA sequence data of four loci (SSU nrDNA, LSU nrDNA, EF-1, RPB2), revealed species of Davidiella to cluster in a separate family (Davidiellaceae) from species of Mycosphaerella (Mycosphaerellaceae), with both families residing in the Capnodiales (Dothideomycetes), and not Dothideales as always presumed.

The current circumscription of Cladosporium emend. can be summarised as follows: Dematiaceous hyphomycetes; Davidiella anamorphs; mycelium internal and external; hyphae branched, septate, pigmented; stromata lacking or occasionally present; conidiophores mononematous, solitary to fasciculate, cylindrical, geniculate-sinuous to nodulose, simple to branched, subhyaline to usually distinctly pigmented, continuous to septate, smooth to verruculose; conidiogenous cells integrated, terminal and intercalary, usually sympodial, with a single to several scars; conidiogenesis holoblastic; conidiogenous loci coronate, i.e., more or less protuberant, composed of a central convex dome, surrounded by a raised periclinal rim, barely to distinctly darkened; conidia solitary or in short to long, simple to branched acropetal chains, amero- to phragmosporous, subhyaline to usually distinctly pigmented, smooth, verruculose, verrucose, echinulate, cristate, hila coronate, more or less protuberant.

The new concept of Cladosporium s. str., supported by molecular data and typical coronate conidiogenous loci and conidial hila, rendered it possible to initiate a comprehensive revision of Cladosporium s. lat. The preparation of a general, annotated check-list of Cladosporium s. lat. was the first step in this direction (Dugan et al. 2004). The aim of the present study, therefore, was to delineate Cladosporium s. str. from other taxa that have in recent years been described in Cladosporium s. lat. To attain this goal isolates were studied under standardised conditions on a set of predescribed media (Schubert et al. 2007b - this volume), and subjected to DNA sequence analysis of the LSU nrRNA gene.

	MATERIALS AND METHODS

TOP Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
Isolates
Isolates used were obtained from the Centraalbureau voor Schimmelcultures (CBS), or freshly isolated from various substrates (Table 1). Strains were cultured on 2 % malt extract plates (MEA; Gams et al. 2007), by obtaining single conidial colonies as explained in Crous (1998). Colonies were subcultured onto fresh MEA, oatmeal agar (OA), potato-dextrose agar (PDA) and synthetic nutrient-poor agar (SNA) (Gams et al. 2007), and incubated under near-ultraviolet light to study their morphology. Cultural characteristics were assessed after 2-4 wk on OA and PDA at 25 °C in the dark, using the colour charts of Rayner (1970). Nomenclatural novelties and descriptions were deposited in MycoBank (www.MycoBank.org).

DNA isolation, sequencing and phylogeny
Fungal colonies were established on agar plates, and genomic DNA was isolated following the CTAB-based protocol described in Gams et al. (2007). The primers V9G (de Hoog & Gerrits van den Ende 1998) and LR5 (Vilgalys & Hester 1990) were used to amplify part of the nuclear rDNA operon spanning the 3' end of the 18S rRNA gene (SSU), the first internal transcribed spacer (ITS1), the 5.8S rRNA gene, the second ITS region and the 5' end of the 28S rRNA gene (LSU). Four internal primers, namely ITS4 (White et al. 1990), LR0R (Rehner & Samuels 1994), LR3R (www.biology.duke.edu/fungi/mycolab/primers.htm), and LR16 (Moncalvo et al. 1993), were used for sequencing to ensure that good quality overlapping sequences are obtained. The PCR conditions, sequence alignment and subsequent phylogenetic analysis followed the methods of Crous et al. (2006d). The ITS1, ITS2 and 5.8S rRNA gene (ITS) were only sequenced for isolates of which these data were not available. The ITS data were not included in the analyses but deposited in GenBank where applicable. Gaps longer than 10 bases were coded as single events for the phylogenetic analyses; the remaining gaps were treated as missing data. Sequence data were deposited in GenBank (Table 1) and alignments in TreeBASE (www.treebase.org).

Morphology
Wherever possible, 30 measurements (x 1 000 magnification) were made of structures mounted in lactic acid or Shear's solution (Gams et al. 2007), with the extremes of spore measurements given in parentheses. Microscopic observations were made from colonies cultivated for 7 d under continuous near-ultraviolet light at 25 °C on SNA as explained in Schubert et al. (2007b - this volume). Three classes of conidia are distinguished. Ramoconidia are defined as short apical branches (often conidiogenous cells) of a conidiophore which secede and function as conidia. They are characterised by having a truncate, undifferentiated base, i.e., they differ from true conidia by lacking characteristic basal hila caused by conidiogenesis. Ramoconidia give rise to branched or unbranched conidia. Secondary ramoconidia are branched conidia with a narrowed base, bearing a true hilum, that can occur in chains, giving rise to conidia, which differ from secondary ramoconidia with regards to shape, size and septation. In previous literature on Cladosporium and allied genera, the true ramoconidia have often been classified as "ramoconidia s. str." whereas the secondary ramoconidia have been named "ramoconidia s. lat."

	RESULTS

TOP Abstract INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References

 
DNA extraction, amplification and phylogeny
Amplicons of approximately 1 700 bases were obtained for the isolates listed in Table 1. The newly generated sequences were used to obtain additional sequences from GenBank, which were added to the alignment. The manually adjusted LSU alignment contained 73 sequences (including the two outgroup sequences) and 996 characters including alignment gaps. Of the 849 characters used in the phylogenetic analysis, 336 were parsimony-informative, 77 were variable and parsimony-uninformative, and 436 were constant. Neighbour-joining analyses using three substitution models on the sequence data yielded trees with identical topologies to one another. The neighbour-joining trees support the same clades as obtained from the parsimony analysis, but with a different arrangement at the deeper nodes, which were poorly supported in the bootstrap analyses or not at all (for example, the Helotiales and Pleosporales are swapped around). Performing a parsimony analysis with gaps treated as new characters increases the number of equally parsimonious trees to 94; the same topology is observed but with less resolution for the taxa in the Helotiales (data not shown). Forty-four equally most parsimonious trees (TL = 1 572 steps; CI = 0.436; RI = 0.789; RC = 0.344), one of which is shown in Fig. 1, were obtained from the parsimony analysis of the LSU sequence data. The cladosporium-like taxa were found to belong to the Helotiales, Pleosporales, Sordariales and as sister taxa to the Davidiellaceae in the Capnodiales.

View larger version (35K): [in this window] [in a new window]   Fig. 1. One of 44 equally most parsimonious trees obtained from a heuristic search with 100 random taxon additions of the LSU sequence alignment using PAUP v. 4.0b10. The scale bar shows 10 changes, and bootstrap support values from 1 000 replicates are shown at the nodes. Thickened lines indicate the strict consensus branches and ex-type sequences are printed in bold face. The tree was rooted to two sequences obtained from GenBank (Athelia epiphylla AY586633 and Paullicorticium ansatum AY586693).

View larger version (33K): [in this window] [in a new window]   Fig. 2. Consensus phylogram (50 % majority rule) of 800 trees resulting from a Bayesian analysis of the LSU sequence alignment using MRBAYES v. 3.1.2. Bayesian posterior probabilities are indicated at the nodes. Ex-type sequences are printed in bold face. The tree was rooted to two sequences obtained from GenBank (Athelia epiphylla AY586633 and Paullicorticium ansatum AY586693).

View larger version (135K): [in this window] [in a new window]   Fig. 3. Rachicladosporium luculiae (type material). A-F. Conidiophores with conidial chains, and conidiogenous loci aggregated in the upper region. G. Conidia. Scale bar = 10 µm.

Capnodiales, incertae sedis
Rachicladosporium Crous, U. Braun & C.F. Hill, gen. nov. MycoBank MB504430.

Etymology: Named after the apical rachis on conidiophores, and its cladosporium-like appearance.

Differt a Cladosporio conidiophoris cum rachibus terminalibus, locis conidiogenis inconspicuis vel subconspicuis, margine leviter incrassatis, non fuscatis et non refractivis, hilis inconspicuis.

Mycelium consisting of branched, septate, smooth, hyaline to pale brown, thin-walled hyphae. Conidiophores erect, solitary, macronematous, arising from superficial hyphae, subcylindrical, straight to somewhat geniculate-sinuous, medium brown, finely verruculose; basal foot cell without swelling or rhizoids. Conidiogenous cells integrated, terminal, subcylindrical or tips slightly swollen, forming an apical rachis, multilocal, loci terminal and lateral, without evident sympodial proliferation (non-geniculate); conidiogenous loci inconspicuous or subconspicuous by being very slightly thickened along the rim, but neither darkened nor refractive, giving rise to simple or branched chains or solitary conidia. Ramoconidia medium brown, finely verruculose, 0-1-septate, subcylindrical to narrowly ellipsoid; conidia ellipsoid, pale brown, 0(-1)-septate, smooth to finely verruculose; hila inconspicuous; secession schizolytic.

Type species: Rachicladosporium luculiae Crous, U. Braun & C.F. Hill, sp. nov.

Rachicladosporium luculiae Crous, U. Braun & C.F. Hill, sp. nov. MycoBank MB504431. Fig. 3.

Etymology: Named after its host genus, Luculia.

Mycelium ex hyphis ramosis, septatis, levibus, hyalinis vel pallide brunneis, 2-3 µm latis compositum. Conidiophora erecta, solitaria, macronemata, ex hyphis superficialibis oriunda, subcylindrica, recta to geniculata-sinuosa, ad 60 µm longa et 6 µm lata, 3-6-septata, modice brunnea, subtiliter verruculosa, non crassitunicata, ad basim non inflatae et non rhizoideae. Cellulae conidiogenae integratae, terminales, 8-15 x 4-5 µm, subcylindricae, apicem versus attenuatae, apice obtuso, rachidi terminali, locis conidialibus numerosis, 1-2 µm latis, margine leviter incrassatis, non fuscatis et non refractivis. Conidia catenata vel solitaria. Ramoconidia modice brunnea, subtile verruculosa, 0-1-septata, subcylindrica vel anguste ellipsoidea, 10-17 x 4-5 µm; conidia secundaria ellipsoidea, pallide brunnea, 0(-1)-septata, levia vel subtile verruculosa, interdum guttulata, (7-)9-12(-15) x 3(-4) µm; hila inconspicua.

Mycelium consisting of branched, septate, smooth, thin-walled, hyaline to pale brown, 2-3 µm wide hyphae. Conidiophores erect, solitary, macronematous, arising from superficial hyphae, subcylindrical, straight to somewhat geniculate-sinuous, up to 60 µm long, and 6 µm wide, 3-6-septate, medium brown, finely verruculose, thin-walled ( 1 µm), rarely with a single percurrent proliferation; basal foot cell without swelling or rhizoids. Conidiogenous cells integrated, terminal, 8-15 x 4-5 µm, subcylindrical, tapering to an obtuse apex, occasionally slightly swollen at the tip, without distinct sympodial proliferation (non-geniculate), forming a rachis, with several conidiogenous loci, terminal and lateral, 1-2 µm wide, non-protuberant, quite inconspicuous to subconspicuous, very slightly thickened along the rim, but not darkened and refractive; giving rise to simple or branched chains or solitary conidia, thin-walled ( 0.75 µm). Ramoconidia medium brown, finely verruculose, 0-1-septate, subcylindrical to narrowly ellipsoid, 10-17 x 4-5 µm; conidia ellipsoid, pale brown, 0(-1)-septate, smooth to finely verruculose, at times guttulate, (7-)9-12(-15) x 3(-4) µm; hila inconspicuous, neither thickened nor darkened-refractive.

Cultural characteristics: Colonies on PDA erumpent, spreading, with moderate aerial mycelium and smooth, even margins; iron-grey in the centre, olivaceous-grey in the outer region (surface); iron-grey underneath. Colonies reaching 4 cm diam after 1 mo at 25 °C in the dark.

Specimen examined: New Zealand, Auckland, isolated from leaf spots on Luculia sp. (Rubiaceae), 25 Jul. 2004, F. Hill 1059, holotype CBS H-19891, culture ex-type CBS 121620 = CPC 11407.

Notes: Rachicladosporium is morphologically quite distinct from Cladosporium s. str. and allied cladosporioid genera by having an apical conidiophore rachis with inconspicuous to subconspicuous scars and unthickened, not darkened-refractive conidial hila. Due to the structure of the conidiogenous cells, R. luculiae superficially resembles species of the tretic genus Diplococcium Grove (Ellis 1971, 1976; Goh & Hyde 1998). However, there is no evidence for a tretic conidiogenesis in R. luculiae. The conidia are formed holoblastically and separated by a thin septum. Furthermore, in Diplococcium the conidiogenous cells are terminal as well as intercalary, the conidiophores are often branched, and branched conidial chains are lacking or at least less common. Molecular sequence data about Diplococcium species are not yet available, though taxa that have been analysed show affinities to the Pleosporaceae and Helotiales (Wang et al., unpubl. data), whereas Rachicladosporium is allied with the Capnodiales. The ecology of R. luculiae is still unclear, although it has been isolated from lesions on Luculia sp. Fruiting of this species in vivo has not yet been observed, and its pathogenicity remains unproven.

Toxicocladosporium Crous & U. Braun, gen. nov. MycoBank MB504426.

Etymology: Named after ample volatile metabolites produced in culture, and cladosporium-like morphology.

Differt a Cladosporio locis conidiogenis denticulatis, incrassatis et fuscatis-refractivis, sed non coronatis, conidiophoris et conidiis cum septis incrassatis et atrofuscis, et culturis cum metabolitis volaticis toxicis.

Mycelium consisting of branched, septate, dark brown, finely verruculose hyphae. Conidiophores solitary, dimorphic, solitary, macronematous or micronematous, reduced to conidiogenous cells. Macronematous conidiophores subcylindrical, straight to geniculate-sinuous, or irregularly curved, unbranched or branched above, septate, dark brown, finely verruculose, walls thick, septa dark brown; micronematous conidiophores reduced to conidiogenous cells, erect, doliiform to subcylindrical, with slight taper towards the apex. Conidiogenous cells integrated, terminal or lateral, subcylindrical with slight taper towards apex; proliferating sympodially with apical loci protruding and denticle-like, thickened, darkened and refractive, but not coronate. Conidia catenulate in branched or unbranched chains, medium to dark brown, thick-walled, with dark, thick septa, smooth to finely verruculose; ramoconidia septate, prominently constricted at septa, broadly ellipsoid to subcylindrical; conidia ellipsoid to ovoid, pale to medium brown, 0(-1)-septate; hila not coronate, but protruding, thickened, darkened and refractive in ramoconidia, but less obvious in young conidia.

Type species: Toxicocladosporium irritans Crous & U. Braun, sp. nov.

Toxicocladosporium irritans Crous & U. Braun, sp. nov. MycoBank MB504427. Fig. 4.

View larger version (132K): [in this window] [in a new window]   Fig. 4. Toxicocladosporium irritans (type material). A-B, F. Microconidiophores. C-E. Macroconidiophores. G-H. Ramoconidia and conidia. Scale bars = 10 µm.

Mycelium (in PDA) ex hyphis ramosis, septatis, atro-brunneis, minute verruculosis, (2-)3-4 µm latis, ultimo crassitunicatis et crassiseptatis. Conidiophora solitaria, dimorphosa, macronemata et solitaria vel micronemata. Conidiophora macronemata ex hyphis modice brunneis lateraliter oriunda, erecta, subcylindrica, recta, geniculata-sinuosa vel irregulariter curvata, non ramosa vel ad apicem ramosa, 2-7-septata, atro-brunnea, leviter verruculosa, crassitunicata, septa atro-brunnea, 30-60 x 4-6 µm; conidiophora micronemata saepe non septata, raro 1-2-septata, erecta, doliiformes vel subcylindrica, apicem versus leviter attenuata, 10-30 x 2.5-4 µm. Cellulae conidiogenae integratae, terminales vel laterales, subcylindricae, apicem versus leviter attenuatae, 7-12 x 3-4 µm, sympodiales, cum 1-3 locis conidiogenibus, denticulatis, 1-1.5 µm latis, incrassatis, fuscatis-refractivis. Conidia catenulata vel rami-catenulata, modice vel atro-brunnea, crassitunicata, septis incrassatis, fuscatis, levia vel subtile verruculosa; ramoconidia (0-)1(-3)-septata, constricta, late ellipsoidea vel subcylindrica, 7-15 x 3-5 µm; conidia secundaria ellipsoidea vel ovoidea, pallide vel modice brunnea, 0(-1)-septata, (5-)6-8(-10) x (3-)4(-5) µm; hila protuberantes, 1-1.5 µm lata, hila ramoconidiorum incrassata et fuscata-refractiva, vel hila conidiorum secundariorum 0.5-1 µm lata et subconspicua.

Mycelium on PDA consisting of branched, septate, dark brown, finely verruculose, (2-)3-4 µm wide hyphae; walls and septa becoming thickened and darkened with age. Conidiophores solitary, dimorphic, macronematous and solitary, or micronematous, reduced to conidiogenous cells. Macronematous conidiophores subcylindrical, straight to geniculate-sinuous, or irregularly curved, unbranched or branched above, 2-7-septate, dark brown, finely verruculose, walls thick, septa dark brown, 30-60 x 4-6 µm; medium brown hyphae giving rise to lateral, erect branches that become swollen, dark brown, and develop into macronematous conidiophores with thick-walled and dark septa; micronematous conidiophores aseptate, reduced to conidiogenous cells (rarely 1-2-septate, i.e., with 1-2 supporting cells), erect, doliiform to subcylindrical, with slight taper towards the apex, 10-30 x 2.5-4 µm. Conidiogenous cells integrated, terminal or lateral, subcylindrical with slight taper towards apex, 7-12 x 3-4 µm; proliferating sympodially with 1-3 apical loci that can be slightly protruding and denticle-like, 1-1.5 µm wide, thickened, darkened and refractive. Conidia catenulate in branched or unbranched chains, medium to dark brown, thick-walled, with dark, thick septa, smooth to finely verruculose; ramoconidia (0-)1(-3)-septate, prominently constricted at septa, broadly ellipsoid to subcylindrical, 7-15 x 3-5 µm; conidia ellipsoid to ovoid, younger apical conidia pale to medium brown, 0(-1)-septate, (5-)6-8(-10) x (3-)4(-5) µm; hila protruding, 1-1.5 µm wide, thickened, darkened and refractive in ramoconidia, but less obvious in young conidia, where hila are 0.5-1 µm wide.

Cultural characteristics: Colonies on PDA erumpent, spreading, with dense aerial mycelium and smooth, even margins; surface olivaceous-black (centre), olivaceous-grey in outer region; reverse olivaceous-black. Colonies reaching 35 mm diam after 1 mo at 25 °C in the dark; colonies fertile.

Specimen examined: Suriname, Paramaribo, isolated from mouldy paint, Feb. 1958, M.B. Schol-Schwarz, holotype CBS-H 19892, culture ex-type CBS 185.58.

Notes: Toxicocladosporium irritans produces ample amounts of volatile metabolites, which cause a skin rash within minutes of opening an inoculated dish for microscopic examination. Morphologically and phylogenetically it is very similar to Cladosporium s. str., and produces dimorphic conidiophores, which is also commonly observed in Cladosporium. It is distinct by having dark, thick-walled conidial and conidiophore septa, and lacking the typical coronate Cladosporium scar type (David 1997).

Verrucocladosporium K. Schub., Aptroot & Crous, gen. nov. MycoBank MB504432.

Etymology: Named after its frequently coarsely verrucose to warted hyphae, conidiophores and conidia, and cladosporium-like morphology.

Differt a Cladosporio hyphis saepe verrucosis, hyalinis, conidiophoris cylindraceis-filiformibus, rectis, non vel vix geniculatis, non nodulosis, locis conidiogenis leviter incrassatis, distincte fuscatis-refractivis, sed non coronatis, conidiis saepe valde variantibus, saepe irregulariter formatis, grosse verrucosis-rugosis.

Mycelium sparingly branched, hyphae septate, not constricted at septa, hyaline, almost smooth to irregularly rough-walled, coarsely verrucose to warted. Conidiophores arising laterally from creeping hyphae, erect, straight, or somewhat flexuous, narrowly cylindrical to filiform, neither geniculate nor nodulose, unbranched, septate, pale brown, thin-walled, smooth to often irregularly rough-walled or verrucose. Conidiogenous cells integrated, terminal or intercalary, cylindrical, polyblastic, with sympodial proliferation, with loci often crowded at the apex, truncate, barely to slightly thickened, but distinctly darkened-refractive. Ramoconidia cylindrical, aseptate, concolorous with conidiophores, thin-walled, irregularly rough-walled, coarsely verruculose to verrucose-rugose; hila unthickened but somewhat refractive. Conidia in long unbranched or loosely branched chains, obovoid, ellipsoid, fusiform to subcylindrical, with swollen and constricted parts, often appearing irregular in shape and outline, 0-1-septate, pale brown, thin-walled and irregularly rough-walled, verruculose-rugose; hila truncate, barely to slightly thickened, but distinctly darkened-refractive.

Type species: Verrucocladosporium dirinae K. Schub., Aptroot & Crous, sp. nov.

Verrucocladosporium dirinae K. Schub., Aptroot & Crous, sp. nov. MycoBank MB504433. Fig. 5.

View larger version (141K): [in this window] [in a new window]   Fig. 5. Verrucocladosporium dirinae (type material). A. Colonies on MEA. B-C. Conidial chains. D-H. Ramoconidia and conidia. Scale bars = 10 µm.

Mycelium sparse ramosum. Hyphae 1-3 µm latae, septatae, non constrictae, hyalinae, leviae, vel irregulariter verruculosae, interdum verrucosae, tuberculatae, tenuitunicatae. Conidiophora ex hyphis repentibus lateraliter oriunda, erecta, recta, interdum leviter flexuosa, anguste cylindrica vel filiformes, non geniculta, non nodulosa, non ramosa, ad 85 µm longa, 2-3 µm lata, septata, tenuitunicata ( 0.75 µm), pallide brunnea, levia vel saepe irregulariter verrucosa, leviter crassitunicata. Cellulae conidiogenae integratae, saepe terminales, interdum intercalares, cylindricae, angustae, 9-20 µm longae, holoblasticae, sympodiales, locis conidiogenibus 1-3, saepe ad apicem aggregatis, interdum protuberantibus, truncatis, 1-1.8(-2) µm latis, incrassatis et fuscatis-refractivis. Ramoconidia cylindrica, 16-21 x (2-)2.5-3 µm, non septata, pallide brunnea, tenuitunicata, irregulariter verruculosa vel crosse verrucosa-rugosa, ad 4 hilis terminalibus, ad basim late truncata, non attenuata, 2-2.5 µm lata, non incrassata, sed leviter refractiva. Conidia catenata, in catenis longis, non ramosis vel laxe ramosis, plus minusve recta, obovoidea, ellipsoidea, fusiformes vel subcylindricae, sed saepe irregulares, 4-18(-23) x (2-)2.5-3.5 µm, 0-1-septata, ad septa interdum constricta, pallide brunnea, tenuitunicata ( 0.5 µm), irregulariter verruculosa-rugosa, utrinque leviter attenuata, hila truncata, (0.5-)0.8-1.5(-2) µm lata, vix vel leniter incrassata, sed distincte fuscata-refractiva.

Mycelium sparingly branched; hyphae 1-3 µm wide, septate, not constricted at septa, hyaline, smooth to irregularly rough-walled, sometimes coarsely verrucose, with small to large drop-like, tuberculate warts, walls unthickened. Conidiophores arising laterally from creeping hyphae, erect, straight, sometimes slightly flexuous, narrowly cylindrical to filiform, not geniculate, non nodulose, unbranched, up to 85 µm long, 2-3 µm wide, septate, thin-walled ( 0.75 µm), pale brown, smooth to often irregularly rough-walled, verrucose, walls slightly thickened. Conidiogenous cells integrated, mostly terminal, sometimes also intercalary, cylindrical, narrow, 9-20 µm long, conidiogenesis holoblastic, proliferation sympodial, with a single or up to three conidiogenous loci, often crowded at the apex, sometimes situated on small lateral prolongations, loci truncate, 1-1.8(-2) µm wide, thickened and darkened-refractive. Ramoconidia cylindrical, 16-21 x (2-)2.5-3 µm, aseptate, concolorous with conidiophores, thin-walled, irregularly rough-walled, verruculose to coarsely verrucose-rugose, apically with up to 4 hila, with a broadly truncate, non-attenuated base, 2-2.5 µm wide, unthickened but somewhat refractive. Conidia catenate, in long unbranched or loosely branched chains, more or less straight, obovoid, ellipsoid, fusiform to subcylindrical, but often appearing to form band-like structures, with swollen and constricted parts, accordion or fir tree-like and also due to ornamentation often appearing irregular in shape and outline, 4-18(-23) x (2-)2.5-3.5 µm, 0-1-septate, sometimes constricted at the more or less median septum, pale brown, thin-walled ( 0.5 µm), irregularly rough-walled, verruculose-rugose, somewhat attenuated towards apex and base, hila truncate, (0.5-)0.8-1.5(-2) µm wide, barely or slightly thickened, but distinctly darkened-refractive; microcyclic conidiogenesis not observed.

Cultural characteristics: Colonies erumpent, spreading, with catenate, feathery margins and moderate aerial mycelium on PDA. Surface grey-olivaceous, reverse iron-grey. Colonies reaching 25 mm after 1 mo at 25 °C.

Specimen examined: U.K., Somerset, Kingsbury Episcopi, isolated from the lichen Dirina massiliensis (Roccelaceae, Arthoniales), Mar. 2003, A. Aptroot, holotype CBS-H 19883, culture ex-type CBS 112794.

Notes: Verrucocladosporium dirinae was deposited as Cladosporium arthoniae M. Christ. & D. Hawksw., but the name was misapplied. The latter species, described from apothecia of Arthonia impolita on Quercus from Sweden, does not possess clearly visible, distinct conidiogenous loci and hila, and therefore has to be excluded from the genus Cladosporium s. str. and is also easily distinguishable from the newly introduced species above. Furthermore the conidiophores are apically frequently branched and the catenate, ellipsoid conidia are smaller and wider, 6-10 x 4-5 µm (Hawksworth 1979). Due to the conidiogenesis and the structure of the conidiogenous loci and conidia, C. arthoniae is rather close to lichenicolous Taeniolella S. Hughes species. The unique feature of the new genus Verrucocladosporium is its unusual conidial and hyphal ornamentation. Furthermore, it differs from Cladosporium s. str. in having cylindrical-filiform conidiophores, which are neither geniculate nor nodulose, quite distinct, thickened and darkened, but non-coronate conidiogenous loci and often irregularly shaped conidia. Phylogenetially, it is also distinct as a sister taxon to Cladosporium s. str. Concerning differences to other cladosporioid genera, see "key to the genera". Verrucocladosporium dirinae has been isolated from the lichen species Dirina massiliensis, i.e., this species is probably lichenicolous, although its ecology is not quite clear. Fruiting of this species in vivo has not yet been observed. A second unnamed, taeniolella-like, lichenicolous hyphomycete was also present on the thallus of this lichen.

Capnodiales, Teratosphaeriaceae
Devriesia americana Crous & Dugan, sp. nov. MycoBank MB504434. Fig. 6.

View larger version (132K): [in this window] [in a new window]   Fig. 6. Devriesia americana (type material). A-B. Chlamydospore-like structures formed in culture. C-F. Conidiophores giving rise to conidial chains. G-H. Conidia. Scale bars = 10 µm

Differt a D. shelburniensi conidiophoris brevioribus (ad 30 µm longis), leviter latioribus (2-3 µm), ramoconidiis saepe nullis et conidiis 0-1-septatis.

Mycelium consisting of branched, septate, 1.5-3 µm wide hyphae, irregular in width, predominantly guttulate, smooth, forming hyphal strands and hyphal coils; hyphae frequently forming dark brown, thick-walled, intercalary, muriformly septate chlamydospores on PDA in culture. Conidiophores subcylindrical, medium brown, straight to irregularly curved, up to 7-septate and 30 µm tall, 2-3 µm wide, or reduced to conidiogenous cells. Conidiogenous cells terminal or lateral on hyphae, 5-12 x 2-3 µm, medium brown, smooth, guttulate, subcylindrical, mono- to polyblastic; scars somewhat darkened and thickened, but not refractive. Conidia medium brown, guttulate, smooth, in mostly unbranched chains, subcylindrical to narrowly ellipsoidal, tapering towards subtruncate ends, 0-1-septate, (7-)8-12(-16) x 2(-2.5) µm; hila darkened, somewhat thickened, not refractive, 1-1.5 µm wide.

Cultural characteristics: Colonies erumpent, with sparse aerial mycelium on PDA, and smooth, uneven, wide margins, submerged under the agar surface; greenish-black (surface); reverse olivaceous-black; on OA iron-grey (surface). Colonies reaching 8-15 mm diam on PDA after 14 d at 25 °C in the dark; colonies fertile, but sporulation sparse.

Specimen examined: U.S.A., New York, Long Island, isolated from air, F.M. Dugan, holotype CBS-H 19894, culture ex-type CBS 117726 = ATCC 96545 = CPC 5121.

Notes: Until recently, this species was treated as part of the "Phaeoramularia" hachijoensis species complex (Braun et al. 2003). The present strain has conidia that are smaller than those of "Phaeoramularia" hachijoensis, which has ramoconidia that are 1-3-septate, up to 30 µm long, and conidia that are predominantly 1-septate, 10-21 x 2-4 µm (Matsushima 1975). From the illustration provided by Matsushima, it appears that "Phaeoramularia" hachijoensis is indeed a species of Pseudocladosporium U. Braun, a finding which is in agreement with the name Pseudocladosporium hachijoense (Matsush.) U. Braun proposed by Braun (1998).

Devriesia americana is both morphologically and phylogenetically more allied to Teratosphaeria Syd. & P. Syd. than Venturia Sacc. Based on its pigmented conidiophores and catenulate conidia, and scars that are somewhat darkened and thickened, and the formation of chlamydospores in culture, it is allocated to Devriesia Seifert & N.L. Nick. Species of the genus Devriesia are ecologically different, however (Seifert et al. 2004), being soil-borne and thermotolerant. It is possible, therefore, that further collections of this fungus may eventually indicate that it needs to be placed in a distinct genus within the Teratosphaeriaceae. Devriesia americana is the second species of Devriesia with muriform chlamydospores, beside D. shelburniensis N.L. Nick. & Seifert, but the latter species is easily distinguishable by its long and narrow conidiophores (ca 100-200 x 1.5-2.5 µm) and abundant ramoconidia, up to 25.5 µm long, with 0-3 septa. Furthermore, D. shelburniensis is a thermotolerant soil-borne hyphomycete.

Stenella araguata Syd., Ann. Mycol. 28(1/2): 205. 1930. Figs 7-8.

View larger version (131K): [in this window] [in a new window]   Fig. 7. Stenella araguata (syntype material, IMI 34905). A. Leaf spot. B. Conidiophore, conidia and verruculose hypha on leaf surface. C-D. Conidiophore with terminal conidiogenous cells. E-G. Ramoconidia and conidia. Scale bars = 10 µm.

View larger version (123K): [in this window] [in a new window]   Fig. 8. Stenella araguata (CBS 105.75). A-B. Conidiophore fascicles on a pine needle and tap-water agar, respectively. C-D, G. Conidiophores giving rise to conidial chains. E-F, H-J. Conidial chains with ramoconidia and conidia. Scale bars = 10 µm.

Cladosporium araguatum (Syd.) Arx, Genera of Fungi Sporulating in pure Culture, Edn 2 (Vaduz): 224. 1974.

= Cladosporium castellanii Borelli & Marcano, Castellania 1: 154. 1973.

Leaf spots hypophyllous, irregular to subcircular, up to 8 mm diam, indistinct, yellow to pale brown with indistinct margins on IMI 15728(a); on IMI 34905 (Fig. 7) lesions are amphigenous, and fascicles and sporodochia are rare, with superficial mycelium being predominant. Mycelium consisting of internal and external, medium brown, septate, branched, verruculose, 3-4 µm wide hyphae. Caespituli fasciculate to sporodochial, hypophyllous, medium brown, up to 120 µm wide and 60 µm high. Conidiophores arising singly from superficial mycelium, or aggregated in loose to dense fascicles arising from the upper cells of a brown stroma up to 70 µm wide and 30 µm high; conidiophores medium brown, finely verruculose, 1-5-septate, subcylindrical, straight to geniculate-sinuous, unbranched or branched, 20-40 x 3-4 µm. Conidiogenous cells terminal or lateral, unbranched, medium brown, finely verruculose, tapering to slightly or flat-tipped loci, proliferating sympodially, 5-20 x 3-4 µm; scars thickened, darkened and refractive. Conidia solitary or catenulate, in simple chains, medium brown, verruculose, subcylindrical to narrowly obclavate, apex obtuse, base bluntly rounded with truncate hilum, straight, 0-3-septate, (7-)13-20(-25) x 3(-3.5) µm; hila thickened, darkened, refractive, 1-1.5 µm wide.

Description based on CBS 105.75 (Fig. 8): Mycelium consisting of branched, septate, verruculose, medium brown, 2-4 µm wide hyphae. Conidiomata brown, superficial, sporodochial, up to 200 µm diam Conidiophores solitary, erect, micro- to macronematous, 1-12-septate, subcylindrical, straight to geniculate-sinuous or irregularly curved, 10-70 x 3-4 µm; frequently swollen and constricted at septa, thick-walled, medium brown, verruculose. Conidiogenous cells terminal and intercalary, subcylindrical, straight, but frequently branched laterally, 6-20 x 3-4 µm, with 1-3 flat-tipped loci that can be subdenticulate, 1.5-2 µm wide, somewhat darkened and thickened, not prominently refractive. Conidia medium brown, thick-walled, verruculose, septa becoming darkly pigmented, occurring in branched chains. Ramoconidia subcylindrical to narrowly ellipsoid, 12-25 x 3.5-4(-5) µm, 1(-4)-septate. Conidia occurring in short chains (-8), subcylindrical to narrowly ellipsoid, 0-1(-3)-septate, (7-)10-15(-20) x (2-)3-3.5(-4) µm; hila somewhat thickened, darkened but not refractive, 1.5-2(-2.5) µm wide.

Cultural characteristics: Colonies on OA erumpent, spreading, with moderate aerial mycelium and smooth, even margins; olivaceous-grey (surface); on PDA olivaceous-black (surface), margins feathery, uneven, with moderate aerial mycelium; reverse iron-grey. Colonies reaching 20 mm diam after 1 mo at 25°C in the dark on OA.

Specimens examined: Venezuela, Aragua, La Victoria, on leaf spots of Pithecellobium lanceolatum (Mimosaceae), Jan. 1928, H. Sydow, lectotype of S. araguata (selected here!) IMI 15728(a); 3 Feb. 1928, syntype of S. araguata, IMI 34905. Venezuela, isolated from man with tinea nigra, 1973, D. Borelli, holotype of C. castellanii, IMI 183818, culture ex-type CBS 105.75.

Notes: Stenella araguata is a leaf spot pathogen of Pithecellobium in Venezuela, and represents the type species of the genus Stenella [Two collections were cited, viz. no. 407, `La Victoria', and no. 370, `inter La Victoria et Suata', both without any date, and without any specific type indication. Thus, the two collections have to be considered syntypes. The two IMI collections with different dates are parts of the syntypes, of which IMI 15728(a) is proposed here to serve as lectotype]. Stenella araguata was incorrectly seen as a species of Cladosporium by von Arx (1974), which has recently been morphologically circumscribed (Braun et al. 2003, Schubert et al. 2007b - this volume), and is linked to Davidiella teleomorphs.

In a study by McGinnis & Padhye (1978), Cladosporium castellanii (tinea nigra of human in Venezuela) was shown to be synonymous to Stenella araguata (leaf spots of Pithecellobium lanceolatum in Venezuela). In the present study we re-examined the ex-type strain of C. castellanii (CBS 105.75), and found conidia to be 0-1(-3)-septate, (7-)10-15(-20) x (2-)3-3.5(-4) µm, while those of the type specimen of S. araguata were similar, namely 0-3-septate, (7-)13-20(-25) x 3(-3.5) µm. Furthermore, both collections have verruculose hyphae, which is the primary feature distinguishing Stenella from Passalora Fr. (Crous & Braun 2003).

Stenella has always been used for anamorphs of Mycosphaerella (Crous et al. 2004, 2006c), and the fact that it belongs to Teratosphaeria (Teratosphaeriaceae), and not Mycosphaerella (Mycosphaerellaceae), raised the question of how to treat stenella-like anamorphs in Mycosphaerella. Due to insufficient availability of cultures (Crous et al. 2000, 2001), the status of Stenella was left unresolved (Crous & Braun 2003). Presently (Crous & Groenewald, unpubl. data), it is clear that the stenella-like morphology type is polyphyletic within the Mycosphaerellaceae, and paraphyletic within the Capnodiales. Several species are known that represent morphological transitions between Stenella and Passalora. It seems logical, therefore, that future studies should favour using Passalora to also accommodate Mycosphaerella anamorphs with superficial, verruculose hyphae, which have traditionally been placed in Stenella. This is in spite of the fact that there are other generic names available within the Mycosphaerellaceae for taxa with a stenella-like morphology (pigmented structures, darkened, thickened, refractive scars, and superficial, verruculose mycelium), namely Zasmidium Fr. (1849) (see Arzanlou et al. 2007 - this volume), and Verrucisporota D.E. Shaw & Alcorn (1993). Based on the phylogenetic position of the type species, Stenella s. str. is an anamorph of Teratosphaeria (Teratosphaeriaceae). Using the generic concept as employed in this volume of the Studies in Mycology, however, the anamorph genus is accepted as being poly- and paraphyletic within the order Capnodiales.

Helotiales, incertae sedis
Hyalodendriella Crous, gen. nov. MycoBank MB504435.

Etymology: Morphologically similar to Hyalodendron Diddens.

Differt a Hyalodendro et Retroconi conidiophoris dimorphis, cicatricibus incrassatis et conidiis ultimo brunneis.

Morphologically similar to Hyalodendron and Retroconis, but distinct in that it has dimorphic conidiophores, conidia that turn brown with age, and have thickened scars. Microconidiophores forming as lateral branches on hyphae, subcylindrical, subhyaline to pale brown, smooth, septate, with terminal conidiogenous cells. Macroconidiophores septate, subcylindrical, straight to curved, subhyaline to pale brown, smooth, with an apical rachis that is pale brown, smooth, subcylindrical, with numerous, aggregated loci. Conidia limoniform to ellipsoid, aseptate, smooth, pale brown, in short chains, tapering towards ends that are prominently apiculate, prominently thickened and darkened, but not refractive.

Type species: Hyalodendriella betulae Crous, sp. nov.

Hyalodendriella betulae Crous sp. nov. MycoBank MB504436. Fig. 9.

View larger version (144K): [in this window] [in a new window]   Fig. 9. Hyalodendriella betulae (type material). A. Conidiophores on PDA. B-C. Microconidiophores. D-H. Macroconidiophores with fascicles of conidiogenous cells. I. Conidia with darkened, thickened hila. Scale bars = 10 µm.

Mycelium consisting of branched, septate, 1.5-2 µm wide hyphae, smooth, hyaline to pale brown. Conidiophores dimorphic. Type A: Conidiophores forming as lateral branches on hyphae, subcylindrical, subhyaline to pale brown, smooth, 1-6-septate, up to 40 µm long, and 2-3 µm wide. Conidiogenous cells terminal, 5-15 x 2-3 µm, with a single, apical locus, giving rise to an ellipsoidal cell (conidium?) which mostly remains attached, pale brown, with a subacutely rounded apex and truncate base, 5-7 x 3-4 µm, at times forming chains of up to 6 such cells. Type B: Conidiophores 10-20 x 2-3 µm, 1-2-septate, subcylindrical, straight to curved, subhyaline to pale brown, smooth. Conidiogenous cells pale brown, smooth, subcylindrical with numerous, aggregated loci, inconspicuous to subdenticulate and somewhat protruding, 0.5 µm wide, somewhat thickened and darkened. Conidia in chains of 2-3, limoniform to ellipsoid, widest in the middle, aseptate, smooth, pale brown, tapering towards ends that are prominently apiculate, 0.5-1 µm long, 0.5 µm wide, prominently thickened and darkened, but not refractive.

Cultural characteristics: Colonies on PDA slimy, spreading, somewhat erumpent in the centre, with even, catenulate margins, lacking aerial mycelium; surface fuscous-black to olivaceous-black, with patches of cream; reverse fuscous-black with patches of cream. Colonies reaching 25 mm diam on PDA after 1 mo at 25 °C in the dark; colonies fertile with profuse sporulation on SNA.

Specimen examined: Netherlands, Oostelijk Flevoland, Jagersveld, isolated from Alnus glutinosa (Betulaceae), May 1982, W. Gams, holotype CBS-H 19895, culture ex-type CBS 261.82.

Notes: Morphologically Hyalodendriella resembles the genera Hyalodendron and Retroconis de Hoog & Bat. Vegte (de Hoog & Batenburg van der Vegte 1989). It is distinct, however, in its pigmentation, dimorphic conidiophores and conidia. Furthermore, a strain of Retroconis fusiformis (S.M. Reddy & Bilgrami) de Hoog & Bat. Vegte (CBS 330.81) clusters apart from Hyalodendriella, namely in the Chaetomiaceae, Sordariales.

Pleosporales, incertae sedis
Ochrocladosporium Crous & U. Braun, gen. nov. MycoBank MB504437.

Etymology: Named after its pale brown, cladosporium-like conidia.

Differt a Cladosporio et generis cladosporioidibus diversis conidiophoris cum cellulis basalibus T-formibus et/vel cicatricibus non incrassatis, non vel leviter fuscatis-refractivis.

Mycelium consisting of branched, septate hyphae, subhyaline to pale brown, smooth, giving rise to two types of conidiophores. Macronematous conidiophores solitary, erect, arising from superficial hyphae, composed of a subcylindrical stipe, without a swollen or lobed base or rhizoids, with or without a T-shaped foot cell, pale to dark brown; apical conidiogenous apparatus with or without additional branches, branched part, if present, with short branchlets composed of conidiogenous cells and ramoconidia, continuous to septate, wall thin or slightly thicked, pale brown. Conidiogenous cells integrated, terminal or intercalary, subcylindrical to doliiform, pale brown, thin-walled, smooth; unilocal or multilocal, determinate to sympodial, loci conically truncate, subdenticulate, neither thickened, nor darkened-refractive or only slightly darkened-refractive. Micronematous conidiophores integrated in hyphae, reduced to a lateral peg-like locus or erect, frequently reduced to conidiogenous cells, pale brown, smooth, subcylindrical. Conidia occurring in branched chains, fusiform, ellipsoid-ovoid to subcylindrical, 0(-1)-septate, ramoconidia present, pale brown, thin-walled, smooth to finely verruculose, ends attenuated, hila obconically truncate to almost pointed, neither thickened nor darkened-refractive.

Type species: Ochrocladosporium elatum (Harz) Crous & U. Braun, comb. nov.

Ochrocladosporium elatum (Harz) Crous & U. Braun, comb. nov. MycoBank MB504438. Fig. 10.

View larger version (134K): [in this window] [in a new window]   Fig. 10. Ochrocladosporium elatum (CBS 146.33). A-C, E. Microconidiophores. D. Macro- and microconidiophore. F-H. Macroconidiophores. I-J. Ramoconidia and conidia. Scale bars = 10 µm.

Cladosporium elatum (Harz) Nannf., in Melin & Nannfeldt, Svenska Skogsvardsfoereren Tidskr. 32: 397. 1934.

Cadophora elatum (Harz) Nannf., in Melin & Nannfeldt, Svenska Skogsvardsfoereren Tidskr. 32: 422. 1934.

Mycelium consisting of branched, septate, smooth, hyaline, 2-4 µm wide, thin-walled, hyphae, becoming darker brown in places, giving rise to erect conidiophores. Conidiophores either reduced to conidiogenous cells, or well-differentiated, terminal and lateral on hyphae, erect, highly variable, arising from superficial and submerged hyphae, reduced to subdenticulate loci, 1-1.5 µm wide, or well-differentiated, up to 60 µm long, 1-3-septate, 3-4 µm wide, hyaline to medium brown, smooth, thin-walled ( 1 µm). Conidiogenous cells integrated as lateral peg-like loci on hyphal cells, or erect, subcylindrical, up to 25 µm long, 2.5-4 µm wide, with 1-3 terminal loci, occasionally also lateral, 1-1.5 µm wide, not thickened and darkened, but frequently somewhat refractive (mounted in Shear's solution, not lactic acid). Ramoconidia subcylindrical to ellipsoid, hyaline to pale brown, smooth to finely verruculose, 10-40 x 3-5 µm, 0(-1)-septate, giving rise to branched chains of conidia (up to 20 per chain) that are subcylindrical to ellipsoid, aseptate, (7-)8-10(-14) x (3-)4(-4.5) µm, smooth to finely verruculose, olivaceous-brown, thin-walled (up to 0.5 µm), hila 0.5-1 µm wide, neither thickened nor, or barely, darkened refractive.

Cultural characteristics: Colonies erumpent, spreading, fast growing, covering the plate within 1 mo at 25 °C; aerial mycelium abundant, margins smooth on PDA; surface isabelline in centre, umber in outer region; olivaceous-black in reverse.

Specimen examined: Sweden, Iggesund, isolated from wood pulp, Jan. 1976, E. Melin, specimen CBS-H 19896, culture CBS 146.33.

Notes: "Hormodendrum" elatum was originally described from a wooden stump in Germany. The culture examined here was deposited by Melin in 1933 as culture 389:14, isolated from wood chips in Sweden, and described by Nannfeldt, and has since been accepted as authentic for the species. Earlier publications (de Vries 1952, Ho et al. 1999, de Hoog et al. 2000), clearly state that this species does not belong in Cladosporium s. str., and this statement is supported by the phylogenetic analysis placing it in the Pleosporales.

Ochrocladosporium frigidarii Crous & U. Braun, sp. nov. MycoBank MB504439. Fig. 11.

View larger version (120K): [in this window] [in a new window]   Fig. 11. Ochrocladosporium frigidarii (type material). A. Macro- and microconidiophores. B. Foot cell of macroconidiophore. C-D. Microconidiophore. E-J. Macroconidiophores. K. Conidia. Scale bars = 10 µm.

Differt a O. elato conidiophoris distincte dimorphis, macroconidiophoris majoribus, ad 600 x 5-7 µm, septis incrassates, cellulis basalibus T-formibus et conidiis leniter brevioribus et latioribus, (6-)7-8(-10) x (4-)4.5-5(-6) µm.

Mycelium consisting of branched, septate, 2-7 µm wide hyphae, occasionally constricted at septa with hyphal swellings, subhyaline to pale brown, smooth, thin-walled, giving rise to two types of conidiophores. Macronematous conidiophores solitary, erect, arising from superficial hyphae, up to 600 µm long, composed of a subcylindrical stipe, 5-7 µm wide, 10-15(-20)-septate, without a swollen or lobed base or rhizoids, but with a T-shaped foot cell, wall 1 µm wide, guttulate, with thick septa, dark brown, finely verruculose, apical 1-2 cells at times medium brown, giving rise to 1-2 primary branches, 0-1-septate, subcylindrical, thin-walled, pale brown, smooth to finely verruculose, 10-20 x 4-6 µm, giving rise to (1-)2-4 secondary branches, 0-1-septate, subcylindrical, 8-13(-20) x 4-5 µm, or giving rise directly to conidiogenous cells. Conidiogenous cells subcylindrical to doliiform, pale brown, smooth, 8-15 x 3-4 µm, loci somewhat protruding 1-2 µm wide, neither thickened, darkened, nor refractive. Micronematous conidiophores erect, pale brown, smooth, subcylindrical, reduced to conidiogenous cells, or up to 4-septate, 15-90 x 2-3.5 µm, mostly unbranched, rarely branched below; conidiogenous cells subcylindrical, pale brown, smooth to finely verruculose, tapering at apex and sometimes at base, proliferating sympodially via 1(-3) loci, 1-1.5 µm wide, denticle-like, which can appear somewhat darkened; micronematous conidiophores frequently occurring at the base of macronematous conidiophores. Ramoconidia, if present, up to 30 µm long, 0-1-septate. Conidia and ramoconidia ellipsoid to ovoid, aseptate, pale brown, thin-walled ( 0.75 µm), finely verruculose, occurring in branched chains; conidia (6-)7-8(-10) x (4-)4.5-5(-6) µm; hila 0.5-1 µm wide, not darkened, thickened or refractive.

Cultural characteristics: Colonies on PDA erumpent, spreading, with profuse sporulation and moderate aerial mycelium, even margins, olivaceous-grey (surface); reverse olivaceous-black. Colonies covering the dish after 1 mo at 25 °C in the dark.

Specimen examined: Germany, Hannover, isolated from a cooled room, Jan. 1981, B. Ahlert, holotype CBS-H 19897, culture ex-type CBS 103.81.

Notes: Ochrocladosporium frigidarii is characterised by its dimorphic fruiting, and inconspicuous scars and conidial hila, which are distinct from Cladosporium s. str. The phylogenetic analysis of its LSU sequence places it in the Pleosporales, together with O. elatum.

The dimorphic conidiophores seen in O. frigidarii (CBS 103.81) are less obvious in O. elatum (CBS 146.33), but the scars and hila are similar. The macronematous conidiophores of O. frigidarii are much longer and wider and the conidia are shorter and slightly wider, (6-)7-8(-10) x (4-)4.5-5(-6) µm, than those of O. elatum which are (7-)8-10(-14) x (3-)4(-4.5) µm.

Incertae sedis
Rhizocladosporium Crous & U. Braun, gen. nov. MycoBank MB504440.

Etymology: Named after the presence of rhizoids on its conidiophores, and cladosporium-like conidia.

Differt a Cladosporio et generis cladosporioidibus diversis hyphis hyalinis, conidiophoris cum cellulis basalibus lobatis vel rhizoidibus, cellulis conidiogenis monoblasticis, determinatis, locis margine leviter incrassatis et fuscatis, non refractivis, non coronatis, ramoconidiis brunneis sed conidiis hyalinis, hilis non incrassatis, non fuscatis-refractivis.

View larger version (151K): [in this window] [in a new window]   Fig. 12. Rhizocladosporium argillaceum (type material). A-E. Conidiophores with pigmented ramoconidia and hyaline conidia. F. Rhizoids forming at the foot cells of macroconidiophores. Scale bar = 10 µm.

Type species: Rhizocladosporium argillaceum (Minoura) Crous & U. Braun, comb. nov.

Rhizocladosporium argillaceum (Minoura) Crous & U. Braun, comb. nov. MycoBank MB504441. Fig. 12.

Basionym: Cladosporium argillaceum Minoura, J. Ferment. Technol. 44: 140. 1966.

Mycelium consisting of branched, septate, smooth, hyaline, thin-walled, 1.5-2 µm wide hyphae. Conidiophores solitary, macronematous, erect, arising from superficial mycelium; base somewhat inflated, lobed or with rhizoids, up to 10 µm wide; conidiophore stipe subcylindrical, straight to curved, rarely geniculate-sinuous, wall up to 1 µm wide, medium brown, sometimes paler towards the tip, smooth, 1-6-septate, 35-160 µm tall, 4-6 µm wide. Conidiogenous cells terminal, straight, subcylindrical, tapering towards a flat-tipped locus, occasionally once geniculate, with two loci, medium brown, smooth, 15-35 x 4-6 µm; locus flattened, undifferentiated or very slightly darkened and thickened along the rim, not refractive, 1.5-2 µm wide. Conidia occurring in branched chains. Ramoconidia subcylindrical to narrowly ellipsoidal, straight to geniculate-sinuous, 17-35 x 4-5 µm, medium brown, smooth, thin-walled, frequently branching laterally, with apical and lateral subdenticulate conidial hila, 1.5-2.5 µm wide; secondary ramoconidia hyaline or subhyaline. Conidia aseptate, (10-)12-17(-20) x (3.5-)4(-4.5) µm, in branched chains (-6), hyaline or subhyaline, guttulate, ellipsoidal-fusiform, with obtuse ends, or tapering to obconically subtruncate ends with hila that are inconspicuous (neither darkened nor refractive or thickened), 0.5-1 µm wide.

Cultural characteristics: Colonies on PDA spreading, erumpent, with smooth, even margins and sparse to moderate aerial mycelium; hazel to fawn (surface); reverse hazel to fawn. Colonies reaching 35 mm diam after 1 mo at 25 °C in the dark; colonies fertile.

Specimen examined: Japan, Yoku Island, isolated from decayed myxomycete, 21 Oct. 1961, K. Tubaki No. 4262 holotype, culture ex-type CBS 241.67 = IFO 7055.

Notes: The lobed-rhizoid conidiophore base, and brown, disarticulating ramoconidia, with hyaline chains of conidia, are characteristic of Rhizocladosporium. Although Minoura (1966) illustrated some conidiophores that were micronematous (reduced to conidiogenous cells on superficial mycelium), these were not observed in the present study. Metulocladosporiella Crous, Schroers, J.Z. Groenew., U. Braun & K. Schub. (Crous et al. 2006a) (Herpotrichiellaceae), comprising two banana leaf-spotting pathogens, is another cladosporioid hyphomycete genus having distinct rhizoid hyphae at the swollen base of conidiophores. It differs, however, in having conidiophores terminally branched in a metula-like manner and distinct conidiogenous loci and conidial hila. Pleurotheciopsis B. Sutton (Ellis 1976) is also characterised by having pigmented conidiophores and hyaline or pale, septate conidia formed in acropetal chains, but the conidiophores proliferate percurrently, the conidiogenous cells are polyblastic and ramoconidia are lacking, i.e., the conidia are formed in unbranched chains. Parapleurotheciopsis P.M. Kirk (Kirk 1982) is very similar to Rhizocladosporium. The conidiophores possess a single terminal unilocal conidiogenous cell giving rise to a single ramoconidium which forms several chains of acropetal, aseptate, hyaline to pale olivaceous conidia. The base of the conidiophores is somewhat swollen and lobed [except for Parapleurotheciopsis coccolobae R.F. Castañeda & B. Kendr., Castañeda & Kendrick (1990), with at most slightly swollen, but unlobed base]. However, R. argillaceum occasionally has once-geniculate conidiogenous cells with two loci. Furthermore, it clusters in the Helotiales (Fig. 1), whereas a sequenced strain of Parapleurotheciopsis inaequiseptata (MUCL 41089), belongs to the Xylariales (Fig. 2). The occasionally occurring conidiogenous cells with two loci and the aseptate conidia connect Rhizocladosporium with Subramaniomyces Varghese & V.G. Rao (Varghese & Rao 1979, Kirk 1982) in which, however, terminal ramoconidia are lacking. Furthermore, the type species, S. fusisaprophyticus (Matsush.) P.M. Kirk, frequently has branched conidiophores. Subramaniomyces simplex U. Braun & C.F. Hill (Braun & Hill 2002), a species with unbranched conidiophores is, however, morphologically similar to R. argillaceum, but the genus Subramaniomyces is phylogenetically distinct and also belongs to the Xylariales (CBS 418.95, Fig. 2).

Key to Cladosporium and morphologically similar genera
(bearing simple or branched acropetal chains of amero- to phragmosporous blastoconidia)

• 1. Conidiophores and conidia hyaline............................................................................................................................................................ 2
  
• 1. At least conidiophores pigmented............................................................................................................................................................. 4
  
• 2. Conidia in simple chains........................................................................................................................................................... Hormiactis
  
• 2. Conidia in branched chains....................................................................................................................................................................... 3
  
• 3. Conidiogenous cells sympodial, with distinct conidiogenous loci (scars), thickened and darkened; conidia amero- to phragmosporous; plant pathogenic, leaf-spotting fungi (Mycosphaerella anamorphs; Mycosphaerellaceae)........................................................ Ramularia
  
• 3. Terminal conidiogenous cells with denticle-like loci, giving rise to ramoconidia which form simple or branched conidial chains; lignicolous........................................................................................................................................................................... Hyalodendron [Conidiophores dimorphic; mycelium, conidiophores and conidia at first hyaline, later turning pale brown; conidia in short chains, see Hyalodendriella]
  
• 4(1). Conidia distoseptate, in simple chains............................................................................................................................................. Lylea
  
• 4. Conidia aseptate or euseptate.................................................................................................................................................................. 5
  
• 5. Conidiophores little differentiated, micronematous to semimacronematous; conidiogenous loci undifferentiated, truncate, neither distinctly thickened nor darkened or only very slightly so.......................................................................................................................... 6
  
• 5. Conidiophores well-differentiated, semimacronematous (but multilocal and/or conidiogenous loci well-differentiated) to macronematous....................................................................................................................................................................................... 12
  
• 6. Conidiophores and conidia delicate, thin-walled, in long, easily disarticulating chains............................................................................. 7
  
• 6. Conidiophores and conidia robust, wall thickened, dark, conidial chains often seceding with difficulty.................................................... 9
  
• 7. Conidiophores semimacronematous, simple to often irregularly branched; conidia delicate, narrow, 1-3 µm wide, hyaline to pale olivaceous............................................................................................................................................................................ Polyscytalum
  
• 7. Conidiophores unbranched, micronematous or semimicronematous, integrated in ordinary hyphae, forming minute, lateral, monoblastic, determinate, peg-like protuberances to semimacronematous, forming short lateral branches (conidiophores) with several inconspicuous to denticle-like loci............................................................................................................................................................. 8
  
• 8. Phialidic synanamorphs often present, but sometimes also lacking; saprobic, rarely plant pathogenic, often human pathogenic (Herpotrichiellaceae, Chaetothyriales)......................................................................................................................... Cladophialophora
  
• 8. Without phialidic synanamorphs; saprobic or plant pathogenic (Venturia, Venturiaceae)........