Abstract

Introduction

Identification and classification of morphologically little-differentiated hyphomycetes have always been challenging. Species producing chlamydospores or similar propagules offer few morphological characters to guide taxonomists. The traditional Saccardoan approach to delimiting genera by the pigmentation and septation of spores and the cells that produce them, and the further refinements offered by studies of conidium ontogeny (including conidial secession) and cultural characteristics, provide additional information. The occurrence of synanamorphs or sexual stages also offers clues.

Phylogenetic studies using DNA provide clarity about relationships and give clues as to what phenotypic characters might be phylogenetically informative, facilitating the integration of morphologically depauperate hyphomycetes among more differentiated, often teleomorph-based taxa. Based on SSU and ITS sequence data, Hambleton et al. (2005) attempted to correlate differences in the details of conidium development with phylogenetic relationships among species with chlamydospores or aleuriconidia. Their definitions for chlamydospores and aleurioconidia were based on those from the first Kananaskis conference (Kendrick 1971). Chlamydospores were defined as “thick-walled, thallic, terminal or intercalary spores” formed on vegetative mycelium which “are not dispersed and do not secede until the adjacent hyphal cells dissolve away”, and hence are functionally a kind of “resting spores”. Aleurioconidia were defined as solitary, holothallic or monoblastic conidia produced on somewhat differentiated conidiophores or from conidiogenous cells, which are propagules and can be dispersed. Two relatively large hyphomycete genera that are central to the question of the integration of such fungi into fungal taxonomy are Humicola and Trichocladium. The spores produced by the species of these genera challenge the definitions separating the terms conidium, aleurioconidium, and chlamydospore, in part because there are so many intermediate forms. In this paper, we use these terms fairly loosely, with conidium used for lateral or terminal propagules that seem likely to secede and be dispersed, and chlamydospores for intercalary spores that seem likely to remain in the substrate and not be dispersed, i.e., resting spores. In these fungi, the occurrence of spore release by rhexolytic secession, necessary for strict use of the term aleurioconidium, is inconsistent and can be difficult to observe; for that reason, we do not use this term in the descriptions in this paper.

The hyphomycete genus Humicola was introduced by Traaen (1914) for two species, H. fuscoatra (the type) and H. grisea. Both species produce thick-walled, pigmented and usually single-celled spores. These spores are formed laterally or terminally on hyphae or minimally differentiated conidiophores. Although, in earlier studies, they have been called chlamydospores (Traaen, 1914, De Bertoldi, 1976) or aleurioconidia (Hambleton et al. 2005), based on the definitions discussed above, we call these propagules conidia. This basic morphology, a round spore in a hypha or on a stalk, is about as simple a sporulating morphology can be. Up to now, more than 50 species were described in Humicola (e.g. Nicoli and Russo, 1974, De Bertoldi, 1976, Jiang et al., 2016, Wang et al., 2016a, Wang et al., 2016b), but the genus has never been comprehensively revised, nor has a thorough phylogenetic analysis been undertaken.

Trichocladium (Harz 1871) is a phragmoconidial counterpart of Humicola, differentiated by the production of darkly pigmented, septate conidia. As reviewed by Goh & Hyde (1999), it includes 18 species that, despite their simple morphology, encompass a significant heterogeneity in conidial shape, pigmentation, and development. Hambleton et al. (2005) were surprised that the ITS sequences of H. grisea and the type species of Trichocladium, T. asperum, were identical, suggesting that the two species at least belong to the same genus. Some of the species of both genera also produce an inconspicuous acremonium-like synanamorph (Gams 1971), and the conidia may also have pale or thin-walled pore-like areas that might represent germ pores (Hambleton et al. 2005).

Both Humicola and Trichocladium have been associated with Chaetomiaceae (Seifert et al. 2011). As defined by its type species, Humicola is commonly considered an asexual genus in the Chaetomiaceae (Gams, 1971, Kirk et al., 2008). However, there is evidence of a close relationship between asexual Humicola species and ascoma-producing species in the Chaetomiaceae (Zhang et al. 2017b). Several species within Chaetomiaceae produce humicola-like conidia together with ascomata and ascospores (von Arx et al. 1986, Decock & Hennebert 1997, Wang and Zheng, 2005a, Wang and Zheng, 2005b). Among those, three species were classified in the genus Farrowia: F. longicollea (type species = Chaetomium longicolleum), F. seminuda (= Chaetomium seminudum) and F. malaysiensis (= Chaetomium malaysiense). Farrowia was characterized by ascomata with synchronously produced terminal hairs arising from elongated cells that fused to form a “distinct neck-like structure” below the perithecial apex (Hawksworth 1975). However, Farrowia was not accepted in subsequent monographs (Carter 1982, von Arx et al. 1986), although Untereiner et al. (2001) accepted the genus on the basis of the phylogenetic analysis of LSU sequences. In that study, the three Farrowia species clustered closely with C. homopilatum, C. floriforme, and C. sphaerale, which produce a humicola-like morph and ascomata lacking conspicuous necks. Detailed multi-locus molecular studies on the relationship and taxonomy of species producing chaetomium-like ascomata and/or humicola-like asexual structures are lacking.

Other species with similar thick-walled conidia, classified in various hyphomycete genera, have a similar ecology and may also be associated with Chaetomiaceae. A few genera with more developed conidiophores, but similar conidia and conidiogenesis to Humicola, are also relevant to the phylogenetic reevaluation of asexual members of Chaetomiaceae presented in this paper. Botryotrichum, with its setose, macronematous conidiophores bearing clusters of thick-walled conidia, has long been associated with Chaetomium, following the association of the type species B. piluliferum with its sexual state (Daniels 1961). Two other genera were not previously associated with Chaetomium sexual states but were revealed to partly belong to Chaetomiaceae by our phylogenetic studies. Gilmaniella was separated from Humicola and Botryotrichum by its branched conidiophores and the conidia with a conspicuous germ pore (Barron 1964). The conidiophores of Staphylotrichum species are also similar to those of Botryotrichum but do not terminate in setae (Nonaka et al. 2012).

Just because a species is morphologically simple, it does not mean it is biologically or economically unimportant. Most Humicola species are isolated from soil, while some are from compost, rotting plant materials, indoor environments or even fur of cats (Cooney and Emerson, 1964, Tiscornia et al., 2009, Betancourt et al., 2013, Wang et al. 2016b). Some Humicola species have potential as bio-organic fertilisers or as biological control organisms of plant diseases, such as Verticillium wilt of cotton and Phytophthora blight of pepper (Ko et al., 2011, Lang et al., 2012, Yang et al., 2014a, Yang et al., 2014b). The invalidly named thermophilic species Mycothermus thermophilus (≡Scytalidium thermophilum = Humicola insolens) attracts considerable attention for its remarkable ability to produce thermostable enzymes used to decompose polymeric carbohydrates (Salles et al. 2005, Ghatora et al. 2006, Du et al., 2013, Souza et al., 2013, Yang et al., 2014a, Yang et al., 2014b, Xia et al., 2015). This fungus also contributes to mushroom production by promoting the growth of Agaricus bisporus mycelium (Straatsma & Samson 1993). Some species are reported to have a negative effect on human health (Betancourt et al., 2013, Mejia et al., 2014). Humicola species can cause allergic reactions, and in two reports Humicola species are mentioned as the causal agent of peritonitis (Wang et al. 2011, Ogawa et al., 2002, Kita et al., 2003, Burns et al., 2015).

Earlier research started the reevaluation of Humicola- and Trichocladium-like species that are not associated with Chaetomiaceae. Table 2 in Hambleton et al. (2005) summarized the phylogenetic relationships, conidial characters, and synanamorphs of several chlamydosporic or “aleurioconidial” genera associated with Hypocreales, Pezizales, and Eurotiales. They described the new genus Leohumicola in the order Leotiomycetes, which exhibits an intermediate morphology between Humicola and Trichocladium, with lateral or terminal conidia with a dark brown terminal cell and a paler basal cell. One species of Trichocladium, T. opacum, was transferred to a new genus Pleotrichocladium in the Melanommataceae (Pleosporales) based on the phylogenetic analyses of SSU, LSU and ITS sequences (Hernández-Restrepo et al. 2017). These preliminary steps indicate that the classification of species and genera with humicola-like or trichocladium-like conidia needs a complete taxonomic update.

In this study, the generic delimitation of Chaetomiaceae members that produce humicola- or trichocladium-like asexual spores was re-evaluated using a four-locus phylogeny and morphological data. The phylogenetic relationships of Humicola, the core group of Trichocladium, and related genera are clarified, and the species in these genera are (re-)described and illustrated.

Materials and methods

Results

Phylogeny

Delimitation of Chaetomiaceae

A phylogram based on rpb2 sequence data was constructed to delimit the Chaetomiacae and to show the relationship of the species and genera investigated in this study (Fig. 1). Our rpb2 sequences were combined with available sequence data generated from (reference) strains belonging to the Chaetomiaceae, Lasiosphaeriaceae and Sordariaceae in the Sordariales.

Open in a separate window

Open in a separate window

Fig. 1

Phylogenetic tree inferred from a Maximum-Likelihood analysis of the rpb2 gene region alignment. The confidence values are indicated at the notes: bootstrap proportions from the ML analysis (before the backslash), the MP analysis (after the backslash) above branches, and the posterior probabilities from the Bayesian analysis below branches. The “-” means lacking statistical support (<70 % for bootstrap proportions from ML or MP analyses; <0.95 for posterior probabilities from Bayesian analyses). The branches with full statistical support (ML-BS = 100 %; MP-BS = 100 %; PP = 1.0) are highlighted by thickened branches. Genus and species clades are discriminated with boxes of different colours. The scale bar shows the expected number of changes per site. The tree is rooted with Microascus trigonosporus strain CBS 218.31.

In total, 207 isolates representing 155 taxa were studied, including 91 strains of 13 other Chaetomiaceae genera (Wang et al. 2016b). Microascus trigonosporus CBS 218.31 (Microascales) was selected as an outgroup. The alignment consisted of 901 characters including gaps. Of these, 345 characters were constant, 506 characters were parsimony-informative, and 50 characters were parsimony-uninformative. For the Bayesian inference, the GTR+I+G model was selected based on the results of the MrModel Test. Species producing humicola-like or trichocladium-like conidia fell into four clades: the Humicola lineage (ML-BS = 78 %; MP-BS < 70 %; PP = 1.00), the Mycothermus lineage (ML-BS = 100 %; MP-BS = 100 %; PP = 1.00), the Staphylotrichum lineage (ML-BS = 70 %; MP-BS = 100 %; PP = 0.98) and the Trichocladium lineage (ML-BS 97 %; MP-BS = 100 %; PP = 1.00). The Remersonia lineage (ML-BS 100 %; MP-BS = 100 %; PP = 1.00) forms a sister to the Mycothermus lineage (ML-BS 100 %; MP-BS = 100 %; PP = 1.00) and this lineage includes species that produce conidia on synnemata rather than on hyphae or hypha-like conidiophores like those in the other four lineages. Thermomyces verrucosus clustered within the genus Botryotrichum. Gilmaniella humicola, the type species of this genus, falls in one of the clades in the polyphyletic Lasiosphaeriaceae. However, CBS 388.75, the type of Gilmaniella macrospora, belongs to the Trichocladium lineage.

Four-locus phylogeny

The concatenated alignment included 173 isolates representing 125 taxa, including 91 representatives of 13 other genera in the family. The alignment contained 3 264 characters (including gaps) and is composed of four partitions: 864 characters for rpb2, 1 125 characters for tub2, 701 characters for ITS and 574 characters for the D1/D2 regions of LSU. Of them, 1 215 characters were constant, 1 584 were parsimony-informative, and 465 were parsimony-uninformative. For the Bayesian inference, the GTR+I+G model was selected as optimal for all four partitions based on the results of the MrModel Test. All of the five lineages recognised in the rpb2 alignment were supported with robust support: the Humicola lineage (ML-BS = 82 %, MP-BS = 100 %, PP = 0.95), the Mycothermus lineage (ML-BS = 100 %, MP-BS = 100 %, PP = 1.00), the Remersonia lineage (ML-BS = 99 %, MP-BS = 100 %, PP = 1.00), the Staphylotrichum lineage (ML-BS = 98 %, MP-BS = 100 %, PP = 0.99) and the Trichocladium lineage (ML-BS = 99 %, MP-BS = 100 %, PP = 0.96) (Fig. 2). The rpb2 and the concatenated phylogenetic analyses recognised the species inside in the five target lineages with robust statistical support (> 70 % BS, > 0.95 PP). Twenty-three species clades were recognised in the Humicola lineage, including the type species Humicola fuscoatra. In the Trichocladium lineage, thirteen species clades were recognised. Among the species recognised on the traditional morphology-based concept of Trichochladium, only the type species T. asperum is retained here in this Trichocladium lineage. Seven clades are present in the Staphylotrichum lineage. The known species S. coccosporum, S. boninense, the sexually reproducing species S. longicolleum (= Chaetomium longicolleum) and four new species belong to this lineage. The type species and a potentially novel taxon were distinguished in both the Mycothermus lineage and the Remersonia lineage.

Open in a separate window

Open in a separate window

Fig. 2

Phylogenetic tree resulting from a Maximum-Likelihood analysis of the concatenated rpb2, tub2, ITS and LSU gene region alignment, with the confidence values indicated at the notes same to the rpb2 phylogenetic tree (Fig. 1). The “-” means lacking statistical support (<70 % for bootstrap proportions from ML or MP analyses; <0.95 for posterior probabilities from Bayesian analyses). The branches with full statistical support (MP-BS = 100 %; ML-BS = 100 %; PP = 1.0) are highlighted by thickened branches. Genus and species clades are discriminated with boxes of different colours. The scale bar shows the expected number of changes per site. The tree is rooted with Microascus trigonosporus strain CBS 218.31.

Mycothermus and Remersonia (tub2 phylogeny)

Remersonia was originally proposed as a monotypic genus. In our rpb2 phylogeny and four-locus phylogeny, two distinctive taxa were identified. The (ex)-type material of R. thermophila is no longer available for this study, and in order to compare and combine our sequence data with that of Natvig et al. (2015), another longer fragment of tub2 region needed to be analysed. Five Remersonia sequences and twelve Mycothermus sequences were included in the alignment, and the length of the data set was 1 815 characters including gaps. Of these characters, 1 303 were constant, 349 were parsimony-informative, and 163 were parsimony-uninformative. For the Bayesian inference, the HKY+G model was selected based from the results of the MrModel Test. Similar to the four-locus phylogeny, the tub2 analysis revealed the presence of two distinct clades in the Remersonia lineage and two distinctive clades in the Mycothermus lineage (Fig. 3). The isolates CBS 784.85 and CBS 183.81 were confirmed to be potentially new taxa.

Open in a separate window

Fig. 3

An unrooted phylogenetic tree from ML analysis for the identification of species in Remersonia and Mycothermus based on the longer tub2 alignment. The confidence values are indicated at the notes same to Fig. 1. The scale bar shows the expected number of changes per site.

Taxonomy

The three mesophilic genera Humicola sensu stricto, Staphylotrichum and Trichocladium are re-defined, and the thermophilic genus Mycothermus is validated below. In addition, the morphological diversity of the thermophilic genus Remersonia is presented, and Thermomyces verrucosus is combined in Botryotrichum. Forty-six species are (re-)described and illustrated, including 14 new species and 28 new combinations (incl. two new names).

Botryotrichum verrucosum (Pugh, Blakeman & Morgan-Jones) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824410. Fig. 4.

Open in a separate window

Fig. 4

Botryotrichum verrucosum (CBS 116.64, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 3 wk incubation. B–E. Hyphae, conidiophores and conidia. Scale bars = 10 μm.

Basionym: Thermomyces verrucosus Pugh, Blakeman & Morgan-Jones, Trans. Brit. Mycol. Soc. 47: 116. 1964.

Micromorphology: Somatic hyphae hyaline, 1.5–4.5 μm wide. Conidiophores producing laterally from hyphae, unbranched, occasionally branched once, cylindrical, hyaline to slightly pigmented, septate, often conspicuously thickened and pigmented at septa, 4–45(–65) × 2.5–4 μm. Conidiogenous cells subhyaline to pale brown, cylindrical or slightly swollen as doliiform, holothallic. Conidia solitary, olivaceous brown, globose to subglobose, conspicuously warted, (12.5–)14–15.5(–17) μm.

Culture characteristics: Colonies on OA 28–32 mm diam after 7 d at 25 °C; edge entire; hyaline, obverse white because of aerial hyphae, fuscous black near the edge when old; reverse uncoloured. Colonies on CMA 30–36 mm diam after 7 d at 25 °C; edge entire; obverse white because of aerial hyphae; reverse uncoloured. Colonies on MEA 17–23 mm diam after 7 d at 25 °C, edge entire; texture floccose because of aerial hyphae; obverse white with mouse grey centre and edge; reverse dark mouse grey. Colonies on PCA 24–30 mm diam after 7 d at 25 °C; edge entire; obverse white because of hyaline aerial hyphae; reverse uncoloured.

Material examined: England, Lincolnshire, isolated from salt-marsh soil of mature dunes, Jan 1962, G. Morgan-Jones, ex-type culture CBS 116.64 = ATCC 22222 = IMI 096466ii = MUCL 30565 = VKM F-3568.

Notes: This species was originally classified in Thermomyces (Pugh et al. 1964). Thermomyces verrucosus is a mesophile, and earlier studies show that this species belongs to the Chaetomiaceae (Mouchacca, 1997, Houbraken et al., 2014), but the exact taxonomic position within the family remained unknown. Our phylogenetic analyses (Fig. 1, Fig. 2) indicated that Th. verrucosus resides in a clade with Botryotrichum piluliferum, B. atrogriseum and B. peruvianum. It lacks the branched conidiophores and sterile setae typically observed in B. piluliferum or B. peruvianum.

Humicola Traaen, Nytt Mag. Naturvidensk. 52: 31. 1914. MycoBank MB8566.

Type species: Humicola fuscoatra Traaen.

Asexual morphs producing conidia arising laterally, intercalary or terminally from hyphae without differentiated conidiophores, sometimes together with acremonium-like conidiophores, occasionally only acremonium-like conidiophores present. Ascomata absent or present, when present superficial, or covered by aerial hyphae, ostiolate. Terminal hairs seta-like, flexuous, undulate, coiled or arcuate with apices incurved to coiled. Asci clavate, with 8 biseriate or irregularly arranged ascospores, evanescent before ascospores become mature. Ascospores limoniform to quadrangular, bilaterally flattened, with an apical germ pore.

Notes: Humicola is re-defined and re-established here centred around species phylogenetically allied with the type species, H. fuscoatra. Fifteen Humicola species produce ascomata together with asexual morphs. Of the eight species that now only exhibit an asexual morph in culture, three originally were deposited in the CBS collection under their sexual morph name: CBS 815.97 (ex-type of Humicola floriformis, deposited as Chaetomium floriforme), CBS 120095 (as Chaetomium longicolleum) and CBS 147.67 (ex-type of H. wallefii, as Ch. wallefii). Humicola sensu stricto is characterised by the presence of conidia on hyphae without differentiation of conidiophores, and the co-occurrence of an acremonium-like morph in some species. Ascospores, if present, are limoniform to quadrangular and bilaterally flattened with an apical germ pore.

Humicola ampulliella (X. Wei Wang) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824419. Fig. 5.

Open in a separate window

Fig. 5

Humicola ampulliella (CBS 116735, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Mature ascomata on OA, top view. C. Mature ascomata on OA, side view. D–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Asci. I. Ascospores. Scale bars: D–F = 20 μm; G–I = 10 μm.

Basionym: Chaetomium ampulliellum X. Wei Wang, Nova Hedwigia 81: 248. 2005.

Micromorphology: Ascomata superficial, ostiolate, leaden black with pale luteous to amber hairs in reflected light, elongate obpyriform, obclavate or ampulliform below, apically attenuated to an elongate conical or short cylindrical neck, 160–260 μm high, 65–130 μm diam at the widest part, with the neck part about 40–120 μm long, 29–45 μm wide in the middle portion. Ascomatal wall brown, composed of angular and irregular cells, or elongated to cylindrical cells in the neck part in surface view. Terminal hairs arising from the extension of the adjacent ostiolar cells, seta-like and delicate, smooth, tapering and fading to hyaline towards the tips, 1.5–3 μm diam near the base, usually surrounded by several closely septate, long, thick and seta-like hairs which are 3.5–6 μm diam near the base. Lateral hairs similar to thick terminal ones, tapering and fading towards the tips. Asci narrowly clavate to cylindrical, with spore-bearing part 22.5–34.5 × 6–9.5 μm and stalks about 7–21.5 μm long, with 8 biseriate or uniseriate ascospores, evanescent. Ascospores rust brown when mature, limoniform, prominently umbonate at both ends, bilaterally flattened, (6.5–)7–8.5(–9.5) × 5.5–6.5(–7.5) × 3.5–4.5 μm, with an apical germ pore. Conidia usually oblate, ellipsoidal or subglobose, sometimes obovoid to pyriform, arising laterally or terminally from the hyaline aerial hyphae, solitary, sometimes two cells in chains or several in clusters, fawn, (7–)8–12(–14) × (6–)7–9(–9.5) μm.

Culture characteristics: Colonies on OA 33–39 mm diam after 7 d at 25 °C; edge entire or slightly crenate; obverse showing leaden black mature ascomata mixed with young ascomata covered by pale luteous to amber ascomata hairs, and sparse white aerial hypha; soluble pigment absent; reverse uncoloured. Colonies on CMA similar to those on OA, 31–37 mm diam after 7 d at 25 °C. Colonies on MEA 29–35 mm diam after 7 d at 25 °C; edge entire, obverse showing a thin layer of white aerial mycelium mixed with sparse ascomata; reverse saffron to ochreous. Colonies on PCA 27–33 mm diam after 7 d at 25 °C, edge entire; translucent; aerial hyphae absent; soluble pigment absent; reverse uncoloured.

Material examined: China, Fujian province, Wuyi Mountain, isolated from a discarded sock, Aug 2003, X. W. Wang, ex-type culture CBS 116735 = CGMCC 3.6696; Hunan province, Changsha, isolated from soil under a tree, X. W. Wang, Jun 2003, culture CBS 116736 = CGMCC 3.6697.

Notes: This species can easily be distinguished from other species by the production of delicate ostiolar hairs, narrowly clavate to cylindrical asci, limoniform ascospores that are prominently umbonate at both ends and oblate to ellipsoidal conidia.

Humicola atrobrunnea X. Wei Wang, Houbraken, Y.L. Jiang & T.Y. Zhang, sp. nov. MycoBank MB824420. Fig. 6.

Open in a separate window

Fig. 6

Humicola atrobrunnea (HSAUPII₀₅-1004, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–C. Hyphae and conidia. Scale bars = 10 μm.

Etymology: The epithet refers to the dark brown conidia of this species.

Micromorphology: Somatic hyphae hyaline, 1–4.5 μm wide. Conidia produced laterally on the side of vegetative hyphae, occasionally terminally on the short branches of hyphae, single-celled, olivaceous with dark brown thick wall, solitary, sometimes 2–3 in chain or several in cluster, smooth, globose, subglobose to oblate, occasionally obovoid or pyriform, (7–)8–11(–13.5) μm high, (7–)8–10(–10.5) μm wide.

Culture characteristics: Colonies on OA 30–36 mm diam after 7 d at 25 °C; edge entire; aerial hyphae thin, obverse white, becoming olivaceous along the edge because of the formation of conidia; reverse uncoloured. Colonies on CMA 28–34 mm diam after 7 d at 25 °C; morphology similar to those on OA. Colonies on MEA 29–35 mm diam after 7 d at 25 °C; edge entire or slightly lobate, obverse white; texture floccose because of the hyaline aerial hyphae; reverse uncoloured. Colonies on PCA 29–35 mm diam after 7 d at 25 °C; edge entire; aerial hyphae sparse or absent, obverse olivaceous around the centre; reverse olivaceous around the centre.

Material examined: China, Guizhou, isolated from garden soil, 2004, Y.L. Jiang (holotype CBS H-23481, culture ex-type HSAUPII₀₅-1004 = CBS 114167).

Notes: This species is morphologically similar to H. fuscoatra, but can be distinguished by its more thick-walled and darker conidia.

Humicola christensenii X. Wei Wang & Houbraken, sp. nov. MycoBank MB824422. Fig. 7.

Open in a separate window

Fig. 7

Humicola christensenii (CBS 117760, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 5 wk incubation. B. Part of the colony on OA. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Structure of ascomatal wall in surface view. I. Terminal ascomatal hairs. J. Asci. K. Ascospores. Scale bars: E = 20 μm; F = 50 μm; G–K = 10 μm.

Etymology: Named in memory of Dr Martha Christensen, who isolated the ex-type culture of this species.

Micromorphology: Ascomata superficial, ostiolate, leaden black with honey hairs in reflected light, ovoid, obpyriform or obclavate below, apically attenuated to an elongate conical or short cylindrical neck, 160–240 μm high, 105–150 μm diam at the widest part, with the neck part about 30–50 μm long, 32–42 μm wide in the middle. Ascomatal wall brown, composed of angular and irregular cells in surface view. Terminal hairs arising around ostiolar pore, erect in the lower part, smooth to slightly punctulate, closely septate, 3–5 μm diam near the base, flexuous, undulate or slightly and loosely coiled in the upper part, often constricted at septa, tapering and fading towards the tips. Lateral hairs seta-like, closely septate. Asci clavate, with spore-bearing part 18–32 × (7–)8–11 μm and stalks about 7–15 μm long, with 8 biseriate or irregularly arranged ascospores, evanescent. Ascospores rust brown when mature, limoniform, umbonate at both ends, bilaterally flattened, 6.5–7.5(–8) × 5.5–6 × 3.5–4.5 μm, with an apical germ pore. Conidia subglobose to oblate, sometimes obovoid, arising laterally, intercalary or terminally from the hyaline aerial hyphae, solitary, sometimes two cells in chains, fawn, 5.5–9 μm diam.

Culture characteristics: Colonies on OA 30–36 mm diam after 7 d at 25 °C; edge entire or slightly crenate; obverse showing a thick layer of irregularly distributed white aerial mycelium covering ascomata; soluble pigment olivaceous; reverse olivaceous to brown vinaceous. Colonies on CMA similar to those on OA, 30–36 mm diam after 7 d at 25 °C. Colonies on MEA 33–39 mm diam after 7 d at 25 °C; edge entire; obverse showing a relatively thin layer of white aerial mycelium; sporulation absent; reverse cinnamon to fuscous black. Colonies on PCA 26–32 mm diam after 7 d at 25 °C; edge entire; obverse showing sparse aerial hyphae; translucent; soluble pigment absent; reverse uncoloured.

Material examined: USA, Minnesota, isolated from soil, unknown date, M. Christensen (holotype CBS H-23482, culture ex-type CBS 127760 = RMF 9051).

Notes: Humicola christensenii can be distinguished from Humicola homopilata (= Chaetomium homopilatum) by the production of terminal hairs that are undulate or loosely coiled in the upper part, and by smaller ascospores (6.5–7.5 × 5.5–6 × 3.5–4.5 μm vs 8–9 × 6–7 × 4–5.5 μm).

Humicola cuyabenoensis (Decock & Hennebert) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824423. Fig. 8.

Open in a separate window

Fig. 8

Humicola cuyabenoensis (CBS 398.97, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Mature ascomata on OA, top view. C. Mature ascomata on OA, side view. D. Apical structure of the ascoma. E–G. Ascomata mounted in lactic acid. H. Hyphae and conidia. I. Structure of ascomatal wall in surface view. J. Asci. K. Ascospores. Scale bars: D = 20 μm ; E–G = 100 μm; H–K = 10 μm.

Basionym: Chaetomium cuyabenoensis Decock & Hennebert, Mycol. Res. 101: 309. 1997.

Synonym: Farrowia cuyabenoensis (Decock & Hennebert) D. Hawksw., Syst. Ascomycetum 16: 52. 1998.

Micromorphology: Ascomata superficial, ostiolate, leaden black in reflected light, elongate obpyriform, obclavate or ampulliform below, apically attenuated to a cylindrical, thread-like neck with a truncate apex, (550–)1 000–1 500(–2 400) μm high, 55–100 μm diam at the widest part, with the neck part usually (760–)950–1 360(–2 300) μm long, 20–27.5 μm wide. Ascomatal wall brown, composed of angular cells or elongated to cylindrical cells at the neck part in surface view. Terminal hairs arising from the extension of the adjacent ostiolar cells with pointed tips and forming a fimbriate apex of ascoma, smooth, 1.5–3.5 μm diam near the base, less than 80 μm long. Lateral hairs sparse, scattered on the whole ascoma including the side of the neck, seta-like, tapering and fading towards the tips. Asci narrowly clavate to clavate, occasionally cylindrical, with spore-bearing part 17–29 × 5–9.5 μm and stalks 7–17 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivaceous brown when mature, broad limoniform, umbonate at both ends, bilaterally flattened, 6–7 × 5.5–6.5 × 3.5–4.5 μm, with an apical germ pore. Conidia globose or subglobose, sometimes piriform or clavate, usually 6.5–10.5 μm diam.

Culture characteristics: Colonies on OA 26–32 mm diam after 7 d at 25 °C; edge entire; aerial hyphae very sparse or absent; soluble pigment amber or absent; reverse partly amber. Colonies on CMA similar to those on OA, 22–28 mm diam after 7 d at 25 °C. Colonies on MEA 25–31 mm diam after 7 d at 25 °C; edge entire; obverse fulvous, with a thin layer of grey-white aerial mycelium; reverse fulvous to orange or sienna. Colony on PCA 21–27 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; soluble pigment absent; reverse uncoloured.

Material examined: Ecuador, Sucumbios province, Reserva de Producciόn Faunistica Cuyabeno, isolated from rainforest, unknown date, C. Decock, ex-type culture CBS 398.97 = MUCL 38838.

Notes: This species is distinct from the other Humicola species by the production of ascomata with long, cylindrical necks sparsely covered by lateral hairs and the short terminal hairs on the fimbriate apex of the ascomata. Furthermore, the ascospores are prominently umbonate at both ends.

Humicola degenerans X. Wei Wang & Houbraken, sp. nov. MycoBank MB824424. Fig. 9, Fig. 10.

Open in a separate window

Fig. 9

Humicola degenerans (CBS 232.65, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B. Mature ascomata on OA, top view. C. Mature ascomata on OA, side view. D–E. Ascomata mounted in lactic acid. F. Hyphae and conidia. G. Asci. H. Ascospores. Scale bars: D–F = 20 μm; G–H = 10 μm.

Open in a separate window

Fig. 10

Morphological variety of Humicola degenerans (CBS 780.71). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E. Ascomata mounted in lactic acid. F. Hyphae and conidia. G. An ascoma showing structures of the apex and ascomatal wall in surface view. H. Asci. I. Ascospores. Scale bars: E, G = 20 μm; F, H, I = 10 μm.

Etymology: The epithet refers to the degenerated terminal ascomatal hairs which are sparsely produced or even absent.

Micromorphology: Ascomata superficial to immersed in the medium, solitary to aggregated, ovoid to obpyriform, with a short conical ostiolar beak, 58–145 μm high, 35–80 μm diam. Ascomatal wall brown, textura angularis with the beak part composed of vertically arranged rectangle cells; amorphic and deliquescent cells surrounding the ostiolar opening in surface view. Terminal hairs sparse, 1.5–3 μm diam near the base, or absent. Lateral hairs sparse, seta-like, tapering and fading towards the tips. Asci clavate, with spore-bearing part 22–28 × 10–16 μm and stalks 4–11 μm long, with 8 irregularly arranged ascospores, evanescent. Ascospores olivaceous brown when mature, limoniform, bilaterally flattened, apiculate to umbonate at both ends, 9–10(–10.5) × 7–8 × 5–6.5 μm, with an apical germ pore. Conidia globose to subglobose, subhyaline to pale olivaceous, lateral, or terminal on the hyphae or short branches of hyphae, solitary, 7–10.5 μm diam.

Culture characteristics: Colonies on OA 35–41 mm diam after 7 d at 25 °C; edge entire; obverse greenish black because of a great number of ascospores released and gathered on the top of each of the ascomata; aerial hyphae absent; soluble pigment honey to ochreous; reverse uncoloured or olivaceous grey because of a number of ascomata immersed into the medium. Colonies on CMA similar to those on OA, 37–43 mm diam after 7 d at 25 °C. Colonies on MEA 33–39 mm diam after 7 d at 25 °C; edge entire; obverse mouse grey with white floccose aerial hyphae near the central area; reverse sienna caused by soluble pigment diffusing into the medium. Colonies on PCA 32–38 mm diam after 7 d at 25 °C; edge entire; aerial hyphae absent, soluble pigment absent, reverse uncoloured.

Material examined: Angola, Rio Chipin vila Rob. Williase, isolated from a termite mound, unknown date, E. Müller, culture CBS 780.71. Canada, Ontario; Guelph, isolated from soil under mixed forest, Aug 1964, G.L. Barron (holotype CBS H-23483, culture ex-type CBS 232.65 = IMI 109880 = OAC 10275). USA, Kansas, isolated from soil, unknown date and collector, culture CBS 127324.

Notes: This species is similar to Humicola seminuda and can be distinguished by the apical structures of ascomata, which are usually hyaline with rare terminal hairs. The morphology of CBS 780.71 (Fig. 10) differs from the type (Fig. 9): the ascomata are smaller (55–95 μm vs 110–145 μm high, 35–60 μm vs 45–80 μm diam), aggregated and often immersed or sub-immersed in the medium, with transparent ascomatal wall and only a few asci inside. Based on phylogenetic data, both strains are identified as Humicola degenerans.

Humicola distorta (L.M. Ames) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824427. Fig. 11.

Open in a separate window

Fig. 11

Humicola distorta (CBS 417.66, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E. Ascomata mounted in lactic acid. F. Hyphae and conidia. G. Structure of ascomatal wall in surface view. H. Terminal ascomatal hairs. I. Asci. J. Ascospores. Scale bars: E = 50 μm; F–J = 10 μm.

Basionym: Chaetomium distortum L.M. Ames, Monograph Chaetomiaceae: 21. 1963.

Micromorphology: Ascomata superficial, ostiolate, citrine or greenish olivaceous in reflected light because of ascomatal hairs, subglobose or ovate, 100–150 μm high, (60–)75–120 μm diam. Ascomatal wall brown, textura angularis in surface view. Terminal hairs straight or arcuate, apically incurved, circinate to coiled, slightly verrucose, brown, closely septate, 2–3.5 μm diam near the base. Lateral hairs flexuous or recurved. Asci clavate, with spore-bearing portion 20–25 × 8.5–10.5 μm and stalks 7–12 μm long, with 8 irregularly arranged ascospores, evanescent. Ascospores olivacous brown when mature, limoniform, biapiculate or umbonate at both ends, bilaterally flattened, (6–)6.5–7.5(–8) × 5–6(–6.5) × 3.5–4.5 μm, with an apical germ pore. Conidia globose to oblate, sometimes obovoid or pyriform, hyaline or subhyaline, produced laterally, or terminally on the hyphae or short branches of hyphae, solitary, 6.5–14.5 μm high, 7–9 μm diam.

Culture characteristics: Colonies on OA 26–32 mm diam after 7 d at 25 °C; edge entire; obverse citrine to greenish olivaceous or grey olivaceous because of ascomatal hairs mixed with ascospore masses; aerial hyphae absent, soluble pigment absent; reverse olivaceous buff. Colonies on CMA similar to those on OA, 27–33 mm diam after 7 d at 25 °C. Colonies on MEA 22–28 mm diam after 7 d at 25 °C; edge entire, obverse honey to olivaceous buff because of slowly developing young ascomata mixed with white aerial mycelium; soluble pigment absent; reverse ochreous, fawn to olivaceous. Colony on PCA 26–32 mm diam after 7 d at 25 °C; edge entire; aerial hyphae absent, soluble pigment absent; reverse uncoloured.

Material examined: USA, Iowa, isolated from a dead leaf of Populus tremuloides, unknown date, G.W. Martin, ex-type culture CBS 417.66.

Notes: This species produces ascomatal hairs that are similar to those of some species of Arcopilus. Arcopilus species do not produce an asexual morph, and their ascospores are usually more or less inequilateral. If they are limoniform, then they have germ pores at both ends (H. distorta produces ascospores with one apical germ pore).

Humicola floriformis (Gené & Guarro) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824429. Fig. 12.

Open in a separate window

Fig. 12

Humicola floriformis (CBS 815.97, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–C. Hyphae and conidia. D. Hyphae, conidia and acremonium-like synanamorph. Scale bars = 10 μm.

Basionym: Chaetomium floriforme Gené & Guarro, Mycol. Res. 100: 1005. 1996.

Micromorphology: Somatic hyphae hyaline, 1.2–4.5 μm wide. Conidia numerous, produced laterally on the hyphae, sometimes terminally on the short branches of hyphae, smooth, single-celled, olivaceous brown to brown, globose, subglobose, obovoid or pyriform, solitary, often densely in bunch around the hyphae, (6–)7.5–9.5(–12) μm high, (4.5–)6–8(–9) μm wide. Acremonium-like conidiophores arising laterally from hyphae, hyaline, phialidic, unbranched, 5.5–23 μm long, 1.5–3.5 μm wide near the base. Acremonium-like conidia formed basipetally in chains, aseptate, obovoid, ellipsoidal, with a truncated base and a rounded apex, 2.5–3.5 × 1–2 μm. Sexual morph fide Gené & Guarro (1996): Ascomata discrete, superficial, metallic or pale grey in reflected light, obovate, ostiolate, 230–320 × 190–260 μm; Ascomatal wall dark brown, textura angularis in surface view, partly covered by brown and interwoven hyphae. Ascomatal hairs, unbranched, brown, thick-walled, gradually tapering and paling to a rounded tip, regularly septate, prominently constricted at the septa, appearing articulate and readily breaking into cylindrical segments of variable length. Terminal hairs numerous, incurved and forming a dense tuft around the ostiole, with the upper part undulate to loosely coiled, nearly smooth toward the base and finely verrucose toward the tip, 4–7 μm diam near the base, up to 400 μm long. Lateral hairs straight or undulate, finely verrucose, constricted at the septa, gradually tapering and paling to a rounded tip, up to 250 μm long. Asci numerous, clavate, stalked, 8-spored, evanescent, 30–45 × 8.5–11 μm. Ascospores broadly limoniform to nearly spherical, laterally flattened, slightly biapiculate, hyaline and not dextrinoid when young, pale grey at maturity, dark grey in mass, smooth- and rather thick-walled, 7–8.5 × 6–7 × 5–6 μm, with an apical or slightly subapical germ pore.

Culture characteristics: Colonies on OA 40–46 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous because of the formation of a large number of conidia; texture floccose because of a thick layer of hyaline aerial hyphae; reverse uncoloured. Colonies on CMA similar to those on OA, 40–46 mm diam after 7 d at 25 °C; aerial hyphae relatively thin. Colonies on MEA 42–48 mm diam after 7 d at 25 °C; edge entire; texture floccose because of a thick layer of hyaline aerial hyphae; reverse fawn to olivaceous. Colonies on PCA 40–46 mm diam after 7 d at 25 °C; edge entire; aerial hyphae sparse; reverse uncoloured.

Material examined: Thailand, Sukhothai, isolated from fallen leaves, 10 Aug. 1994, J. Gené, ex-type culture CBS 815.97 = MUCL 40181.

Notes: The holotype of H. floriformis (IMI 368520) was isolated from fallen leaves in Sukhothai (Thailand) by J. Gené on 10 Aug. 1994 and the species was described in 1996 (Gené & Guarro 1996). This isolate was deposited in MUCL by J. Gené in 1997, and subsequently sent from the MUCL to CBS. Based on the information from MUCL (locality, substrate and collector), CBS 815.97 should represent the ex-type of the species. The examined culture is degenerated and produces only the asexual morph. According to the original description, this species produces ascomata together with conidia and no acremonium-like synanamorph was described. We observed the same conidia as described in the original publication; however, acremonium-like conidiophores and conidia were also present in CBS 815.97.

Humicola fuscoatra Traaen, Nytt Mag. Naturvidensk 52: 33. 1914. MycoBank MB188714. Fig. 13.

Open in a separate window

Fig. 13

Humicola fuscoatra (CBS 118.14, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B–F. Hyphae and conidia. Scale bars = 10 μm.

Micromorphology: Somatic hyphae hyaline, 1–2.5 μm wide. Conidia produced laterally on the side of vegetative hyphae, occasionally terminally on the short branches of hyphae, single-celled, solitary, sometimes two in chain or a few in cluster, smooth, olivaceous brown, globose, subglobose to oblate, occasionally obovoid or pyriform, (5–)6.5–9(–12.5) μm high, (5.5–)7–9(–10.5) μm wide.

Culture characteristics: Colonies on OA 29–35 mm diam after 7 d at 25 °C, edge entire; obverse olivaceous because of the formation of a large number of conidia; aerial hyphae sparse; reverse pale olivaceous grey to olivaceous grey mainly because of the immersed conidia and smoke grey soluble pigment. Colonies on CMA similar to those on OA, 24–30 mm diam after 7 d at 25 °C; edge slightly crenate. Colonies on MEA 18–24 mm diam after 7 d at 25 °C; edge entire or slightly lobate; obverse greyish sepia to fuscous black, with a thin layer of aerial hyphae and a few (2–4) radiating furrows, reverse greyish sepia. Colonies on PCA 17–23 mm diam after 7 d at 25 °C; edge entire, aerial hyphae rare, obverse greyish sepia to olivaceous in the centre; reverse greyish sepia to olivaceous in the centre.

Material examined: China, Tibet, isolated from soil, May 2008, Y. Hao CGMCC 3.13428. Norway, isolated from soil, 1914, A.E. Traaen, ex-type culture CBS 118.14 = ATCC 22721 = MUCL 8010 = VKM F-3001.

Notes: Humicola fuscoatra and H. grisea (= Trichocladium griseum) are the first two species described in Humicola (Traaen 1914). Based on the original descriptions, Humicola fuscoatra produces an acremonium-like synanamorph. In this study, an acremonium-like synanamorph was observed in the culture of H. grisea rather than H. fuscoatra, indicating that production of an acremonium-like morph is a variable characteristic.

Humicola fuscogrisea Y.L. Jiang & T.Y. Zhang. Mycosystema 28: 649. 2009. MycoBank MB513355. Fig. 14.

Open in a separate window

Fig. 14

Humicola fuscogrisea (CGMCC 3.13790, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B–C. Hyphae and conidia. Scale bars = 10 μm.

Micromorphology: Somatic hyphae hyaline, 1–2.5 μm wide. Conidia produced laterally on the side of vegetative hyphae, occasionally terminally on the short branches of hyphae, single-celled, olivaceous, with dark brown thick wall, solitary, sometimes 2–3(–8) in a chain or several in a cluster, smooth, oblate to subglobose, (6–)6.5–8(–8.5) μm high, (7–)7.5–9(–9.5) μm wide.

Culture characteristics: Colonies on OA 29–35 mm diam after 7 d at 25 °C; edge entire; obverse greenish black because of the formation of conidia; aerial hyphae absent; reverse greenish black. Colonies on CMA similar to those on OA, 31–37 mm diam after 7 d at 25 °C; edge crenate. Colonies on MEA 35–41 mm diam after 7 d at 25 °C; edge entire; about, obverse showing a relatively thin layer of white to buff aerial hyphae; reverse cinnamon. Colonies on PCA 27–33 mm diam after 7 d at 25 °C; edge entire; aerial hyphae absent, obverse olivaceous grey because of the formation of conidia; reverse olivaceous to olivaceous grey.

Material examined: China, Hubei, isolated from soil, 2000, T.Y. Zhang, ex-type culture CGMCC 3.13790.

Notes: This species is similar to H. atrobrunnea but can be distinguished by relatively pale, thin-walled and smaller conidia (6.5–9 μm diam vs 8–11 μm diam), and its greenish black colonies on OA and CMA.

Humicola homopilata (Omvik) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824432. Fig. 15.

Open in a separate window

Fig. 15

Humicola homopilata (CBS 157.55, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 3 wk incubation. B. Part of the colony on OA. C. Mature ascomata on OA, side view. D. Mature ascomata on OA, top view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia together with an ascoma initial. H. Structure of ascomatal wall in surface view. I. Terminal ascomatal hairs. J. Asci. K. Ascospores. Scale bars: E–G = 20 μm; H–K = 10 μm.

Basionym: Chaetomium homopilatum Omvik, Mycologia 47: 749. 1955.

Synonym: Chaetomium amesii Sergejeva, Nov. Syst. Plant. non vasc. P.112. 1965.

Micromorphology: Ascomata superficial, often covered by white aerial hyphae, with pale luteous to amber ascomata hairs in reflected light, ovoid or obpyriform, ostiolate, with a short conical or cylindrical ostiolar beak, 150–210 μm high, 110–160 μm diam. Ascomatal wall brown, textura angularis in surface view, often elongated and radially arranged around the basal cells of the lateral hairs. Terminal hairs seta-like, straight or slightly undulate or flexuous, usually unbranched, closely septate, slightly granulate, olivaceous brown, tapering and fading towards the tips, 3–4.5 μm diam near the base. Lateral hairs similar to the therminal hairs, but relatively sparse and short. Asci clavate, with spore-bearing part 20.5–32 × 9–13 μm and stalks 7–16 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivaceous brown when mature, limoniform, bilaterally flattened, umbonate at both ends, (7.5–)8–9(–9.5) × 6–7 × 4–5.5 μm, with an apical germ pore. Conidia globose to subglobose, occasionally obovoid or obpyriform, hyaline, pale olivaceous, lateral, or terminal on the hyphae or short branches of hyphae, occasionally intercalary, solitary, sometimes two in chains or a few in clusters, (6–)7–8.5(–10) μm long, 7– 8.5(–9) μm wide.

Culture characteristics: Colonies on OA 42–48 mm diam after 7 d at 25 °C; edge entire; obverse white; texture floccose because of aerial hyphae; soluble pigment fuscous black; reverse olivaceous grey to iron grey. Colonies on CMA similar to those on OA, 40–46 mm diam after 7 d at 25 °C. Colonies on MEA 46–52 mm diam after 7 d at 25 °C; edge entire; texture floccose because of a thick layer of white aerial mycelium; soluble pigment dark mouse grey; reverse ochreous to fuscous black. Colony on PCA 41–47 mm diam after 7 d at 25 °C; edge entire; obverse showing white aerial mycelium in the central area; soluble pigment absent; reverse uncoloured.

Material examined: Norway, isolated from filter paper in soil, unknown date, A. Omvik, ex-type culture CBS 157.55. Unknown country, unknown substrate, unknown date, L.M. Ames, culture ex-isotype of Chaetomium amesii CBS 338.68.

Notes: Omvik (1955, Fig. 1-c) observed some tuberculate projections on the surface of the ascomatal hairs, which we did not see in this study. Perhaps the material from which the tuberculate projections are made is soluble in lactic acid. von Arx et al. (1986) adopted a broad concept for C. homopilatum and accepted a large variability in the ascomatal hairs of this species. Our phylogenetic study did not support C. homopilatum sensu von Arx, and the available ex-type cultures of the synonymized species were re-examined. Several species, such as C. distortum, C. pinnatum, C. wallefii and C. udagawae are resurrected and are transferred to Humicola in this paper.

Humicola leptodermospora X. Wei Wang & Houbraken, sp. nov. MycoBank MB824435. Fig. 16.

Open in a separate window

Fig. 16

Humicola leptodermospora (CBS 120095, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 3 wk incubation. B–E. Hyphae and conidia. Scale bars = 10 μm.

Etymology: The epithet refers to the relatively thin-walled conidia of this fungus.

Micromorphology: Somatic hyphae hyaline, 1–5 μm wide. Conidia produced laterally or intercalary on the side of vegetative hyphae, sometimes terminally on the short hyphal branches, single-celled, hyaline when young, then pale olivaceous, solitary, smooth, subglobose, sometimes obovoid, pyriform or irregular-shaped, often wrinkled because of the relatively thin cell walls, (7–)8.5–11(–12.5) μm long, (6–)6.5–8(–8.5) μm diam.

Culture characteristics: Colonies on OA 37–43 mm diam after 7 d at 25 °C; edge entire; obverse showing white floccose aerial hyphae; reverse fawn to olivaceous black. Colonies on CMA similar to those on OA, 36–42 mm diam after 7 d at 25 °C. Colonies on MEA 37–43 mm diam after 7 d at 25 °C; edge entire or crenate; obverse showing white floccose aerial hyphae; reverse olivaceous to olivaceous black. Colony on PCA 37–43 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous because of the formation of conidia; aerial mycelium sparse; reverse uncoloured.

Material examined: Brazil, Estado do Paraná, isolated from forest soil, Mar 2005, J. Guarro & A.M. Stchigel (holotype CBS H-23484, culture ex-type CBS 120095).

Notes: The ex-type culture of H. leptodermospora was deposited as Chaetomium longicolleum in CBS, indicating that this species is able to produce ascomata with a long neck. Chaetomium longicolleum (= Staphylotrichum longicolleum) was revealed to be the sexual morph of Staphylotrichum in this study. In our phylogenetic analyses (Fig. 1, Fig. 2), H. leptodermospora belongs to Humicola rather than Staphylotrichum, implying its ascomata should not be staphylotrichum-like (see “Staphylotrichum” part below for details). The culture is now degenerated and only produces conidia.

Humicola malaysiensis (D. Hawksw.) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824437. Fig. 17.

Open in a separate window

Fig. 17

Humicola malaysiensis (CBS 780.83). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Asci. I. Ascospores. Scale bars: E–F = 20 μm; G–I = 10 μm.

Basionym: Farrowia malaysiensis D. Hawksw., Persoonia 8: 178. 1975.

Synonym: Chaetomium malaysiense (D. Hawksw.) v. Arx, Nova Hedwigia, Beih. 84: 38. 1986.

Micromorphology: Ascomata superficial, ostiolate, greenish black in reflected light, elongate obpyriform, obclavate or ampulliform below, apically attenuated to an elongate conical or short cylindrical neck, 185–365 μm high, 60–90 μm diam at the widest part, with the neck part about 55–125 μm long, 15–25 μm wide in the mid. Ascomatal wall brown, composed of angular and irregular cells and elongated to cylindrical cells in the neck part in surface view. Terminal hairs arising from the extension of the adjacent ostiolar cells with round tips, smooth, partly finger-like, partly long and seta-like, sometimes simply branched, 3–4.5 μm diam near the base. Lateral hairs similar to terminal ones, scattered on the whole ascoma including the side of the neck. Asci narrowly clavate to clavate, occasionally cylindrical, with spore-bearing part 19–28.5 × 8.5–12 μm and stalks about 6–13.5 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivaceous brown when mature, limoniform, biapiculate or slightly umbonate at both ends, bilaterally flattened, 7.5–9 × (6–)6.5–7.5(–8) × 5–6 μm, with an apical germ pore. Conidia globose or subglobose, sometimes obovoid, usually arising laterally or terminally from the aerial hyphae, hyaline to subhyaline, 7–12.5 μm diam.

Culture characteristics: Colonies on OA 43–49 mm diam after 7 d at 25 °C; edge entire; obverse violaceous grey because of the masses of ascospores, aerial hypha sparse in the central part, covering ascomata and mixed with the masses of ascospores; soluble pigment pale luteous or amber to umber, reverse cinnamon to fawn. Colonies on CMA 49–55 mm diam after 7 d at 25 °C; edge entire; white aerial hypha sparse, only in the central point; soluble pigment pale luteous to luteous; reverse grey sepia to olivaceous. Colonies on MEA 30–36 mm diam after 7 d at 25 °C; edge entire; obverse showing white aerial hyphae mixed with ascomata, with an irregular and circled furrow around the center and radiating furrows started from the circle furrow; ascomata concentrated mainly in the center; reverse umber to sienna caused by soluble pigment. Colonies on PCA 41–47 mm diam after 7 d at 25 °C; edge entire; aerial hyphae absent; soluble pigment pale luteous; reverse pale luteous or amber to hazel caused by soluble pigment.

Material examined: Ivory Coast, Kaprémé, isolated from soil, unknown date, M. Dreyfuss, culture CBS 760.83. Japan, Tanegoshima, Kagoshima, isolated from soil, Dec 1958, S. Udagawa, culture CBS 167.61. Malaysia, Selangor, isolated from Elaeis guineensis, 19 March 1974, T. L.Huan, culture ex-type CBS 399.97 = IMI 183184 = MUCL 39402.

Notes: The ascomata of H. malaysiensis resemble those of H. quadrangulata and the ascospores are similar to those of H. seminuda. Humicola malaysiensis can be distinguished from H. quadrangulata by limoniform rather than quadrangular ascospores and from H. seminuda by the production of longer ascomata necks.

Humicola mutabilis X. Wei Wang & Houbraken, sp. nov. MycoBank MB824438. Fig. 18.

Open in a separate window

Fig. 18

Humicola mutabilis (CBS 779.71, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B. Mature ascomata on OA, top view. C. Mature ascomata on OA, side view. D. Hyphae and conidia. E–F. Ascomata together with conidia mounted in lactic acid. G–H. Structures of the apices of ascomata I. Asci. J. Ascospores. Scale bars: E–F = 20 μm; G–I = 10 μm.

Etymology: The epithet refers to the production of ascomata of different shapes.

Micromorphology: Ascomata superficial, solitary, leaden black with buff or amber hairs in reflected light, ovoid, obpyriform, urniform or irregular, with 1–3 ostioles, usually apically nonconverging, 125–200 μm high, 50–140 μm diam. Ascomatal wall brown, textura angularis, often with pale to hyaline, amorphic and deliquescent cells surrounding the ostiolar opening in surface view. Terminal hairs arising from the wall cell around the ostioles, seta-like with a swollen basal cell 3–6 μm diam, sometimes absent. Lateral hairs mainly surrounding apex, seta-like, tapering and fading towards the tips. Asci clavate, with spore-bearing part 25–35 × 10–14 μm and stalks about 12–25 μm long, with 8 irregularly arranged ascospores, evanescent. Ascospores olivaceous brown when mature, limoniform, biapiculate, bilaterally flattened, (8.5–)9–10.5(–11.5) × (6.5–)7–8.5(–10) × 5–6(–6.5) μm, with an apical germ pore. Conidia globose to subglobose, sometimes obovoid or pyriform, subhyaline to olivaceous, lateral or terminal on hyaline hyphae or short branches of hyphae, solitary, 6–12.5 μm diam.

Culture characteristics: Colonies on OA 43–49 mm diam after 7 d at 25 °C; edge crenate; aerial hyphae sparse and distributing irregularly; soluble pigment honey to isabelline; reverse olivaceous grey to dark mouse grey caused by soluble pigment and immersed hyphae with a large number of dark conidia in the medium. Colonies on CMA similar to those on OA, 43–49 mm diam after 7 d at 25 °C; obverse showing relatively dense aerial hyphae which distributed radially from the centre; soluble pigment honey to isabelline; reverse olivaceous grey to dark mouse grey. Colonies on MEA 41–47 mm diam after 7 d at 25 °C; edge entire or crenate; obverse primrose to buff, texture floccose; sporulation absent, reverse sienna caused by soluble pigment and immersed conidia in the medium. Colonies on PCA 39–46 mm diam after 7 d at 25 °C; edge entire; aerial hyphae absent; soluble pigment isabelline; reverse isabelline to dark mouse grey.

Material examined: Israel, Mt. Carmel, isolated from soil, unknown date, T. Leisinger (holotype CBS H-23485, culture ex-type CBS 779.71).

Notes: The ex-type strain of H. mutabilis was deposited in CBS as Chaetomium seminudum. Humicola mutabilis is morphologically similar to H. seminuda (= C. seminudum) and H. degenerans. This species can be distinguished by its asomata that often possess 2–3 ostiole pores and appear variable in shape, and by its buff or amber coloured hairs (in reflected light) that mainly arise from wall cells around the beak. The ascomata of H. seminuda and H. degenerans rarely possess more than one ostiole pore and are regular in shape. The terminal ascomatal hairs of H. seminuda arise from the extension of the adjacent ostiolar cells and are limited in length, while terminal ascomatal hairs of H. degenerans are absent or sparsely produced.

Humicola olivacea X. Wei Wang & Samson, Stud. Mycol. 84: 203. 2016. MycoBank MB818848. Fig. 19.

Open in a separate window

Fig. 19

Humicola olivacea (CBS 142031, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–E. Hyphae and conidia. Scale bars = 10 μm.

Micromorphology: Somatic hyphae hyaline, subhyaline, pale olivaceous to honey or greyish sepia, 1–2.5 μm wide. Conidia produced laterally or intercalary on hyphae, or terminally on the short branches of hyphae, single-celled, olivaceous to dark brown, with dark brown thick wall when old, solitary, sometimes 2(–8) in chains or in cluster, globose, subglobose or broad obovate, (7.5–)8–9.5(–11) × (7–) 7.5–9(–10) μm.

Culture characteristics: Colonies on OA 39–45 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous; aerial mycelium thin, smoke grey; reverse mouse grey. Colonies on CMA similar to those on OA, 38–44 mm diam after 7 d at 25 °C. Colonies on MEA 42–48 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white; texture fluccose; reverse pale luteous to greyish sepia. Colonies on PCA 34–40 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse, white to pale luteous; reverse slightly pale luteous.

Material examined: USA, isolated from dust, 2009, E. Whitfield & K. Mwange, culture ex-type CBS 142031 = DTO 319-C7.

Notes: The ex-type of H. olivacea was examined using the inclined coverslip culture method to determine how the conidia arise from the hyphae. Pigmented aerial hyphae were observed in H. olivacea. The majority of Humicola species usually only produce hyaline aerial hyphae. The conidia were produced laterally, intercalary on hyphae, or terminally on the short branches on hyphae. These short branches on hyphae become slightly pigmented (Fig. 19-E) and these are similar to the pigmented hyphae present in aerial mycelium (Fig. 19-D, E).

Humicola pinnata (L.M. Ames) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824440. Fig. 20.

Open in a separate window

Fig. 20

Humicola pinnata (CBS 467.66, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 3 wk incubation. B. Part of the colony on OA. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Structure of ascomatal wall in surface view. I. Terminal ascomatal hairs. J. Asci. K. Ascospores. Scale bars: E–F = 20 μm; G–K = 10 μm.

Basionym: Chaetomium pinnatum L.M. Ames, Monograph Chaetomiaceae: 33. 1963.

Micromorphology: Ascomata superficial, ostiolate, olivaceous buff to citrine green in reflected light because of ascomatal hairs, subglobose, ovoid or obpyriform, 80–195 μm high, 45–130 μm diam, usually with a short conical to short cylindrical ostiolar beak. Ascomatal wall brown, textura angularis in surface view. Terminal hairs flexuous, distinctly septate, 2–3 μm diam near the base, multi-branched in the upper part, forming a net to keep the ascospore masses, with the branches strongly constricted at septa, appearing to be composed of a chain of fusiform or cymbiform hyaline to subhyaline cells. Lateral hairs seta-like or flexuous. Asci clavate to fusiform, with spore-bearing portion 21.5–27.5 × 8–11.5 μm and stalks 5–12.5 μm long, with 8 biseriate ascospores, evanescent before ascospores mature. Ascospores olivacous brown when mature, limoniform, biapiculate or umbonate at both ends, bilaterally flattened, (6.5–)7–8 × 5–6(–6.5) × (3.5–)4–5 μm, with an apical germ pore. Conidia globose to oblate, sometimes ovoid, hyaline to subhyaline, lateral, intercalary or terminal on the hyphae or short branches of hyphae, without conidiophore differentiation, solitary, 6.5–9.5 μm diam.

Culture characteristics: Colonies on OA 38–44 mm diam after 7 d at 25 °C; edge entire; obverse honey to greenish olivaceous because of ascomatal hairs mixed with ascospore masses, aerial hyphae absent; soluble pigment absent; reverse olivaceous buff. Colonies on CMA similar to those on OA, 36–42 mm diam after 7 d at 25 °C. Colonies on MEA 39–45 mm diam after 7 d at 25 °C; edge entire; aerial mycelium thin; soluble pigment absent; reverse ochreous to fulvous. Colony growth on PCA 31–37 mm diam after 7 d at 25 °C; edge entire; aerial hyphae absent; soluble pigment absent; reverse uncoloured.

Material examined: USA, Arizona, Colorado National Forest, isolated from dead wood, unknown date, G.W. Martin, ex-type culture CBS 467.66.

Notes: von Arx et al. (1986) reduced this species to a synonym of Chaetomium homopilatum (classified as Humicola homopilata in this paper). Humicola pinnata produces asci and ascospores that are similar to those of Humicola homopilata. However, the terminal hairs of H. pinnata are multi-branched in the upper part with the branches strongly constricted at the septa, while the ascomatal hairs of H. homopilata are distinctively different and usually unbranched, seta-like, or slightly undulate or flexuous. The four-gene phylogeny clearly shows that H. pinnata is a separate species, distinct from H. homopilata.

Humicola pulvericola X. Wei Wang, Houbraken & Seifert, sp. nov. MycoBank MB824444. Fig. 21.

Open in a separate window

Fig. 21

Humicola pulvericola (CBS 144165, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B. Hyphae, thick-walled conidia and acremonium-like synanamorph. C. Hyphae and thick-walled conidia. D–F. Acremonium-like synanamorph. Scale bars = 10 μm.

Etymology: The epithet refers to dust, the original substrate from which the ex-type strain was isolated.

Micromorphology: Somatic hyphae hyaline, 1.5–3 μm wide. Conidia produced laterally or intercalary on hyphae, occasionally terminally on the short branches of hyphae, single-celled, olivaceous to dark brown, with dark brown thick wall when old, solitary, sometimes two in chain, smooth, subglobose, or oblate, occasionally piriform to clavate, (7.5–)8.5–11.5(–14) × (5.5–)7.5–9(–11) μm. Acremonium-like conidiophores unbranched, occasionally branched, aseptate or septate, 13–30 × 1–3 μm. Conidiogenous cells phialidic. Conidia in basipetal chains, sometimes in false heads, hyaline, aseptate, smooth, obovoid, usually with a truncated base and a rounded apex, 2.5–4 × 1–2(–2.5) μm.

Culture characteristics: Colonies on OA 51–57 mm diam after 7 d at 25 °C; edge entire or undulated; aerial mycelium thick, white, buff, pale luteous or ochreous; reverse ochreous to olivaceous black. Colonies on CMA similar to those on OA, 46–52 mm diam after 7 d at 25 °C; aerial mycelium white, salmon to peach. Colonies on MEA 46–52 mm diam after 7 d at 25 °C; edge entire; aerial mycelium thick, white, salmon or pale luteous; reverse dark brick. Colonies on PCA 39–45 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse, white to pale luteous; reverse slightly pale luteous.

Material examined: Mexico, isolated from house dust by dilution-to-extinction, 2009, K. Mwange & E. Whitfield (holotype CBS H-23486, culture ex-type CBS 144165 = DTO 318-G9). South Africa, isolated from house dust by dilution-to-extinction, 2009, K. Mwange & E. Whitfield, culture CBS 144166 = DTO 319-B7.

Notes: Conidia together with an acremonium-like morph were observed on slide cultures prepared using the inclined coverslip method. This species is morphologically similar to H. piriformis, but can be distinguished by larger conidia (8.5–11.5 × 7.5–9 μm vs 7–7.5 μm). The species is also characterised by its floccose colonies with thick mycelium on OA and PCA.

Humicola quadrangulata X. Wei Wang & Houbraken, sp. nov. MycoBank MB825446. Fig. 22.

Open in a separate window

Fig. 22

Humicola quadrangulata (CBS 111771, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Part of the colony showing immersed ascomata above which aerial mycelium was removed. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Asci. I. Ascospores. Scale bars: E = 50 μm; F = 20 μm; G–I = 10 μm.

Etymology: The epithet refers to the quadrangular ascospores of this fungus.

Micromorphology: Ascomata superficial, ostiolate, usually covered by thick aerial hyphae, leaden black in reflected light, elongate obpyriform, obclavate or ampulliform below, apically attenuated to a cylindrical, thread-like neck with a slightly conical apex, 290–610 μm high, 55–110 μm diam at the widest part, with the neck part usually 160–450 μm long, 18–32 μm wide in the mid. Ascomatal wall brown, composed of angular and irregular cells or elongated to cylindrical cells at the neck part in surface view. Terminal hairs arising from the limited extension of the adjacent ostiolar cells with pointed tips, smooth, the majority less than 50 μm long, 2–3 μm diam near the base, usually with one of them extending to up to 260 μm long and 3–4 μm diam near the base. Lateral hairs sparse, seta-like, tapering and fading towards the tips. Asci narrowly clavate to clavate, occasionally cylindrical, with spore-bearing part 23–39 × 10.5–15(–17) μm and stalks 5–20 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivaceous brown when mature, quadrangular or nearly so in face view, bilaterally flattened, (9.5–)10–10.5 × (8.5–)9–10(–10.5) × 5.5–6.5 μm, with an apical germ pore. Conidia globose or subglobose, abundant, usually arising laterally from the aerial hyphae, hyaline to subhyaline, 5.5–14 μm diam.

Culture characteristics: Colonies on OA 28–34 mm diam after 7 d at 25 °C; edge fimbriate to crenate; aerial hyphae thick, white; soluble pigment mouse grey to dark mouse grey; reverse partly mouse grey to dark mouse grey. Colonies on CMA similar to those on OA, 21–27 mm diam after 7 d at 25 °C. Colonies on MEA 25–31 mm diam after 7 d at 25 °C; edge entire or slightly crenate; aerial mycelium thick, white; sporulation absent; reverse partly dark brick to sepia. Colony on PCA 24–30 mm diam after 7 d at 25 °C; edge fimbriate to crenate; about, aerial mycelium relatively sparse; soluble pigment absent; reverse uncoloured.

Material examined: Brazil, Corcorvado, isolated from soil, unknown date, R.F. Castaneda-Ruiz (holotype CBS H-23487, culture ex-type CBS 111771).

Notes: The ex-type strain was deposited as Chaetomium cuyabenoensis in CBS. Humicola quadrangulata can be easily distinguished from Humicola cuyabenoensis (Fig. 8) by the production of quadrangular ascospores without umbonate ends and ascomata with a shorter neck without lateral hairs.

Humicola seminuda (L.M. Ames) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824447. Fig. 23.

Open in a separate window

Fig. 23

Humicola seminuda (CBS 368.84, ex-epitype culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 3 wk incubation. B. Mature ascomata on OA, top view. C. Mature ascomata on OA, side view. D. Hyphae and conidia. E. Ascomata together with conidia mounted in lactic acid. F. Structures of the apex of an ascoma. G. Asci. H. Ascospores. Scale bars: D, F = 20 μm; E, G, H = 10 μm.

Basionym: Chaetomium seminudum Ames, Mycologia 41: 642. 1949.

Synonym: Farrowia seminuda (Ames) D. Hawksw., Persoonia 8: 181. 1975.

Micromorphology: Ascomata superficial, obpyriform or ovoid, ostiolate, with a short conical to short cylindrical ostiolar beak, usually apically converging, 130–200 μm high, 50–90 μm diam. Ascomatal wall brown, textura angularis with the beak part composed of vertically elongated cells in surface view. Terminal hairs arising from the limited extension of the adjacent ostiolar cells with pointed or round tips, 1.5–3 μm diam near the base. Lateral hairs sparse, seta-like, and relatively long near the ostioles. Asci clavate to fusiform, with spore-bearing part 20–35 × 11–16.5 μm and stalks 3.5–10 μm long, with 8 irregularly arranged ascospores, evanescent before ascospores become mature. Ascospores olivaceous brown when mature, limoniform, bilaterally flattened, apiculate to umbonate at both ends, (8–)8.5–9.5 × 7.5–8.5 × (4.5–)5–6 μm, with an apical germ pore. Conidia globose to subglobose, sometimes ellipsoidal or obovoid, subhyaline to pale olivaceous, lateral, or terminal on the hyphae or short branches of hyphae, solitary, sometimes two in chains, 8–10.5(–11) μm diam, up to 12 μm long when obovoid.

Culture characteristics: Colonies on OA 48–54 mm diam after 7 d at 25 °C; edge entire; obverse greenish black because of the formation of ascomata; aerial hyphae sparse or absent; soluble pigment buff to honey; reverse honey to hazel. Colonies on CMA similar to those on OA, 45–51 mm diam after 7 d at 25 °C. Colonies on MEA 32–38 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white; soluble pigment absent; reverse cinnamon to sienna. Colony on PCA 42–48 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white; soluble pigment absent; reverse uncoloured.

Material examined: Lectotype designated here: Fig. 23, Fig. 24, Fig. 25, Fig. 26, Fig. 27, Fig. 28, Fig. 29 illustrated by L.M. Ames based on ex-type culture from Iowa, USA in Mycologia 41: 643. 1949. MBT381349. Canada, Ontario, isolated from soil, 13 Apr. 1981, A. Carter & S.A. Redhead, MBT381345 (epitype designated here, CBS H-23488, culture ex-epitype CBS 368.84); Ontario, isolated from soil under Thuja occidentalis, Sep 1964, G.C. Bhatt, culture CBS 549.69. China, isolated from leaf fragment in soil, 25 Apr 1958, G. Sӧrgel, culture CBS 153.59; Xinjiang, Khanas, isolated from soil under yak dung, June 2002, X.W. Wang, culture CBS 119767.

Open in a separate window

Fig. 24

Humicola semispiralis (CBS 723.97, ex-isotype culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Structure of ascomatal wall in surface view. I. Terminal ascomatal hairs. J. Asci. K. Ascospores. Scale bars: E–F = 50 μm; G–K = 10 μm.

Open in a separate window

Fig. 25

Humicola sphaeralis (CBS 985.87, ex-epitype culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Structure of ascomatal wall in surface view. I. Terminal ascomatal hairs. J. Asci. K. Ascospores. Scale bars: E–F = 50 μm; G–K = 10 μm.

Open in a separate window

Fig. 26

Humicola subspiralis (CBS 148.58). A. Colonies from left to right on OA, CMA, MEA and PCA after 3 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae, conidiophores and conidia of acremonium-like synanamorph. H. Structure of ascomatal wall in surface view. I. Terminal ascomatal hairs. J. Asci. K. Ascospores. Scale bars: E–F = 50 μm; G–K = 10 μm.

Open in a separate window

Fig. 27

Humicola udagawae (CBS 337.68, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Hyphae and conidia. H. Structure of ascomatal wall in surface view. I. Terminal ascomatal hairs. J. Asci. K. Ascospores. Scale bars: E–F = 50 μm; G–K = 10 μm.

Open in a separate window

Fig. 28

Humicola wallefii (CBS 147.67, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B–E. Hyphae and conidia. Scale bars = 10 μm.

Open in a separate window

Fig. 29

Mycothermus thermophiloides (CBS 83.81 ex-type). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–G. Hyphae and chlamydospores. Scale bars: B–D = 20 μm; E–G = 10 μm.

Notes: The holotype of Chaetomium seminudum seems to be lost. However, the protologue contains the illustrations that are designated here as the lectotype of C. seminudum, the basionym of H. seminuda. This species is morphologically similar to H. mutabilis and H. degenerans but can be distinguished by the apical structure of ascomata, which usually possess terminal hairs arising from the extension of the adjacent ostiolar cells, and these terminal hairs are limited in length resembling to those of H. mutabilis.

Humicola semispiralis (Udagawa and Cain) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824448. Fig. 24.

Basionym: Chaetomium semispirale Udagawa & Cain, Canad. J. Bot. 47: 1947. 1969.

Micromorphology: Ascomata superficial, ostiolate, with ascomatal hairs pale buff to olivaceous buff in reflected light, spherical, ellipsoidal to ovoid, 270–380 μm high, 190–320 μm diam. Ascomatal wall brown, composed of angular to irregular cells in surface view. Terminal hairs partly straight to flexuous, partly spirally coiled in the upper part, septate, verrucose, 2.5–4.5 μm diam near the base. Lateral hairs straight or flexuous. Asci clavate, with spore-bearing portion 20–26 × 9–12 μm and stalks 11–21.5 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivacous brown to brown when mature, limoniform, umbonate at both ends, bilaterally flattened, (8–)8.5–9.5(–10) × (6–)6.5–8 × 4.5–5.5(–6) μm, with an apical germ pore. Conidia globose to oblate, sometimes ovoid, hyaline, subhyaline to olivaceous, usually lateral on the hyphae or short branches of hyphae, without conidiophore differentiation, solitary, (8.5–)9–11 μm diam.

Culture characteristics: Colonies on OA 36–42 mm diam after 7 d at 25 °C; edge entire; aerial mycelium irregularly distributing, thick, white; texture cottony; soluble pigment ochreous to umber; reverse pale luteous, ochreous to umber. Colonies on CMA similar to those on OA, 37–43 mm diam after 7 d at 25 °C. Colonies on MEA 39–45 mm diam after 7 d at 25 °C; edge entire; non-sporulating, aerial mycelium thick, buff to ochreous; texture floccose; reverse apricot to sienna caused by soluble pigment. Colony on PCA 34–40 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse; soluble pigment absent; reverse uncoloured.

Material examined: Canada, isolated from herbarium specimen of the type of C. semispirale by A. Carter, culture ex-isotype CBS 723.97. The type of C. semispirale was originally isolated from contaminated filter paper, 1958, S. Udagawa & R.F. Cain.

Notes: von Arx et al. (1986) considered Chaetomium semispirale (= Humicola semispiralis) to be a synonym of Chaetomium sphaerale. Based on the original descriptions and our examination of these two species, H. semispiralis can be easily distinghuished from H. sphaeralis by its larger ascospores (8.5–9.5 × 6.5–8 × 4.5–5.5 μm vs 7–7.5 × 5.5–6.5 × 4–4.5 μm), and by the characters of its terminal hairs.

 Two groups of species of Humicola described by de Bertoldi (1976), i.e. i) H. aurea, H. lutea, H. piriforme and H. repens, and ii) H. glauca, H. nivea and H. sardiniae, are closely related to H. semispiralis based on their ITS sequences and are discussed in the “Doubted or excluded species” section below. Other strains and other ITS sequences deposited in GenBank and identified as H. fuscoatra (e.g. KU945926) also seem to belong to this complex, Multigene and morphological analyses of these strains must be completed to determine whether these are synonyms of H. semispiralis, or whether this is a phylogenetic species complex.

Humicola sphaeralis (Chivers) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824449. Fig. 25.

Basionym: Chaetomium sphaerale Chivers, Proc. Amer. Acad. Arts 48: 84. 1912.

Micromorphology: Ascomata superficial, ostiolate, with ascomatal hairs buff to pale luteous in reflected light, ellipsoidal to ovoid, 240–340 μm high, 190–275 μm diam. Ascomatal wall brown, composed of angular to irregular cells in surface view. Terminal hairs flexuous to undulate, septate, verrucose, 2–3.5 μm diam near the base. Lateral hairs straight or flexuous. Asci clavate, with spore-bearing portion 22–30 × 8–13 μm and stalks about 12–26 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivacous brown to brown when mature, limoniform, umbonate at both ends, bilaterally flattened, (6.5–)7–7.5(–8) × 5.5–6.5 × 4–4.5 μm, with an apical germ pore. Conidia globose to oblate, sometimes ovoid, hyaline, subhyaline to olivaceous, usually lateral on the hyphae or short branches of hyphae, without conidiophore differentiation, solitary, 9–12 μm diam.

Culture characteristics: Colonies on OA 42–48 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; soluble pigment buff to honey or absent; reverse isabelline. Colonies on CMA similar to those on OA, 42–48 mm diam after 7 d at 25 °C. Colonies on MEA 45–51 mm diam after 7 d at 25 °C; edge entire; non-sporulating; aerial mycelium thick, white to pale luteous; texture floccose; reverse fuscous black caused by soluble pigment. Colony on PCA 37–43 mm diam after 7 d at 25 °C; edge entire; about, aerial mycelium sparse or absent; soluble pigment absent; reverse uncoloured.

Material examined: France, isolated from soil, unknown date, F. Seigle-Murandi, culture CBS 985.87. USA, Reading, Mass., isolated from a culture of caterpillars, unknown date, A.H. Chivers (holotype, New York Botanical Garden Specimen ID 01050440).

Notes: CBS 985.87 was deposited as Chaetomium semispirale, however, its relatively small ascospores, flexuous to undulate and branched, but never spirally coiled ascomatal hairs correspond well with the characters of the type of C. sphaerale. Chivers (1912) described C. sphaerale producing ascospores measuring 7.3–8.1 × 6.4 μm. von Arx et al. (1986) re-described C. sphaerale, and in his description, the ascospores were 7.5–9 × 6–7 × 4–5 μm, which is larger than in the original description. Our measurement of the type (6–7.5 × 5–6.5 × 4–4.5 μm) confirmed that the size of the ascospores of C. sphaerale is less than 8 × 6.5 μm in face view. The holotype was originally collected in the USA, and epitypification of this species awaits recollection from the type locality.

Humicola subspiralis (Chivers) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824450. Fig. 26.

Basionym: Chaetomium subspirale Chivers, Proc. Amer. Acad. Arts 48: 84. 1912.

Micromorphology: Ascomata superficial, ostiolate, grey white in reflected light because of the ascomatal hairs, spherical, ellipsoidal to ovoid, 240–320 μm high, 185–260 μm diam. Ascomatal wall brown, composed of angular to irregular cells in surface view. Terminal hairs straight or slightly flexuous, undulate to spirally coiled and attenuated in the upper part, septate, 2.5–4.5 μm diam near the base. Lateral hairs similar to the terminal ones, but shorter. Asci clavate, with spore-bearing portion 18–25 × 6–9 μm and stalks 8–25(–31) μm long, with 8 biseriate ascospores, evanescent. Ascospores olivacous brown when mature, limoniform, biapiculate or umbonate at both ends, bilaterally flattened, 5–6.5(–7) × 4.5–5.5(–6) × 3–4 μm, with an apical germ pore. Conidia absent. Acremonium-like conidiophores unbranched, occasionally branched, aseptate or septate, 6–24 × 1.2–3 μm, with phialidic conidiogenous cells. Conidia in basipetal chains, sometimes in false heads, hyaline, aseptate, smooth, obovoid, usually with a truncated base and a rounded apex, 2–3.5 × 1–1.5 μm.

Culture characteristics: Colonies on OA 34–40 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; soluble pigment violaceous black to olivaceous black or absent; reverse leaden black. Colonies on CMA similar to those on OA, 34–40 mm diam after 7 d at 25 °C. Colonies on MEA 30–36 mm diam after 7 d at 25 °C; edge entire; non-sporulating; aerial mycelium pale smoke grey; texture floccose; soluble pigment umber; reverse fuscous black. Colonies on PCA 32–38 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; soluble pigment; reverse uncoloured.

Material examined: China, Chungking, isolated from leaf fragments in soil, 8 Feb 1958, G. Sörgel, culture CBS 148.58; Guangdong Pro., isolated from soil, Aug 2004, X.W. Wang, culture CBS 119768. USA, New England, isolated from cow dung, unknown date A.H. Chiver (holotype, New York Botanical Garden Specimen ID 01050446).

Notes: According to Chivers (1912), the diagnostic characters of Chaetomium subspirale (= Humicola subspiralis) are the ascomatal hairs, especially its lateral hairs, which are different from those of most other species in being undulate to spirally coiled. No asexual stage of this species was mentioned by Chivers. In two subsequent studies, thick-walled conidia were found (Carter 1982, von Arx et al. 1986). In our study, rather than thick-walled conidia, an acremonium-like synanamorph was observed in both cultures. von Arx et al. (1986) pointed out that thick-walled conidia could occasionally be absent in CBS 148.58. Humicola subspiralis can potentially produce both thick-walled conidia and an acremonium-like synanamorph. Further study may find out which factors determine its anamorph type.

Humicola udagawae (Sergejeva ex Udagawa) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824451. Fig. 27.

Basionym: Chaetomium udagawae (Sergejeva) Sergejeva ex Udagawa, Trans. Mycol. Soc. Japan 20: 476. 1979.

Synonym: Chaetomium udagawae Sergejeva, Novosti Syst. Nizsh. Rast. P.110. 1965.

Micromorphology: Ascomata superficial, often covered by white aerial hyphae, usually obovoid and without ostiolar beak, with an inconspicuous ostiole, 100–180 μm high, 70–140 μm diam. Ascomatal wall brown, textura angularis in surface view. Ascomatal hairs seta-like, difficult to distinguish terminal or lateral, straight, unbranched or simply branched, septate, slightly granulate, olivaceous brown, tapering and fading towards the tips, with a swollen basal cell, 2–4.5 μm diam near the base. Asci clavate, with spore-bearing part 20–28 × 9–15 μm and stalks 7–17 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivaceous brown when mature, limoniform, bilaterally flattened, umbonate at both ends, 8–9.5(–10.5) × 6.5–7.5(–8.5) × 4.5–5.5(–6) μm, with an apical germ pore. Conidia globose to subglobose, occasionally obovoid or obpyriform, hyaline, pale olivaceous, lateral, or terminal on the hyphae or short branches of hyphae, occasionally intercalary, solitary, 7–10.5 μm high, 6.5–10.5 μm wide.

Culture characteristics: Colonies on OA 38–44 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white; texture cottony; soluble pigment olivaceous grey; reverse grey olivaceous. Colonies on CMA 37–43 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white; texture cottony; soluble pigment olivaceous grey; reverse greyish sepia to fulvous. Colonies on MEA 36–42 mm diam after 7 d at 25 °C; edge entire; aerial mycelium thick, white to buff; texture cottony; reverse ochreous. Colony on PCA 36–42 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; soluble pigment absent; reverse uncoloured.

Material examined: Unknown country, unknown substrate, unknown date, K.S. Sergejeva, culture ex-type CBS 337.68.

Notes: This species is characterised by obovoid ascomata without ostiolar beak, and inconspicuous ostiole openings.

Humicola wallefii (J.A. Mey. & Lanneau) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824452. Fig. 28.

Basionym: Chaetomium wallefii J.A. Mey. & Lanneau, Bull. Soc. Mycol. France. 83: 320. 1967.

Micromorphology: Somatic hyphae hyaline, 1–3 μm wide. Conidia usually originating on the side of vegetative hyphae, single-celled, solitary, sometimes two in chain or a few in cluster, usually slightly tuberculate, olivaceous brown, globose, subglobose or oblate, (7–)7.5–9.5(–13) μm high, (7–)7.5–9.5(–10) μm wide. Sexual morph degenerated in the culture examined in this study. Fide Meyer & Lanneau (1967): Ascomata ostiolate, dark brown, subglobose or ovoid, solitary, 150–280 × 100–180 μm, setifera, grey-green or dark grey-brown. Ascomatal hairs flexuous to undulate, septate, 2–2.5 μm diam. Asci clavate, up to 50 × 7–8 μm, with 8 ascospores, evanescent. Ascospores light brown, limoniform, bilaterally flattened, biapiculate, 6.5–8 × 4.5–6.5 μm, with an apical germ pore.

Culture characteristics: Colonies on OA 32–38 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white; texture floccose; reverse isabelline to brown vinaceous. Colonies on CMA similar to that on OA, 32–38 mm diam after 7 d at 25 °C; reverse primrose to straw. Colonies on MEA 35–41 mm diam after 7 d at 25 °C; aerial mycelium white; texture floccose; reverse pale luteous to ochreous. Colonies on PCA 28–34 mm diam after 7 d at 25 °C; edge entire; about, translucent, aerial mycelium white, sparse, reverse uncoloured.

Material examined: Zaire, Lumbumbashi, isolated from soil, unknown date, J. Meyer, ex-type culture CBS 147.67 = IMI 126039.

Notes: This species originally produced ascomata and was treated as a synonym of Chaetomium homopilatum (von Arx et al. 1986). The ex-type culture of Humicola wallefii at CBS only produces conidia. The conidia of H. wallefii are slightly tuberculate, while they are smooth in most other Humicola species.

Mycothermus D.O. Natvig et al. ex X. Wei Wang, Houbraken & D. O. Natvig, gen. nov. MycoBank MB824453.

Type species: Mycothermus thermophilus (Cooney & R. Emers.) X. Wei Wang, Houbraken & D. O. Natvig.

Micromorphology: Somatic hyphae hyaline to subhyaline, Chlamydospores holothallic, thick-walled, brown, produced intercalary, laterally or terminally, solitary or in chains or clusters, smooth to verrucose, doliiform, globose, subglobose, oblong or obovoid. Thermophilic.

Notes: The genus Mycothermus and its type species were invalidly published (Art. 42.1) with a single identifier (MB 807382) (Natvig et al. 2015). Here we validate these two names. Based on rpb2 sequence data as well as a multi-gene phylogeny, this genus represents a sister lineage to Remersonia.

Mycothermus thermophiloides X. Wei Wang & Houbraken, sp. nov. MycoBank MB824455. Fig. 29.

Etymology: The epithet to the phenotypic similarity of this species to My. thermophilus.

Micromorphology: Somatic hyphae hyaline, 1.5–6(–7) μm wide. Chlamydospores holothallic, thick-walled, brown, superficial or immersed, produced laterally, intercalary on hyphae, or terminally on the short side branches of hyphae, single-celled, occasionally 2-celled, solitary, sometimes two in chains, smooth to spinose, globose, subglobose, oblate or obovoid, (9.5–)11–15(–19) × (9–)10.5–12(–16) μm.

Culture characteristics: Colonies on OA more than 70 mm diam after 7 d at 37 °C; edge entire; aerial hyphae sparse or absent; obverse pale mouse grey to mouse grey because of the formation of chlamydospores; reverse uncoloured to pale smoke grey. Colonies on CMA similar to those on OA, more than 70 mm diam after 7 d at 37 °C. Colonies on MEA more than 70 mm diam after 7 d at 37 °C; edge crenate, aerial hyphae white to smoke grey; obverse fluccose; reverse greyish sepia. Colonies on PCA more than 70 mm diam after 7 d at 37 °C; edge crenate or lobate; aerial hyphae absent; obverse pale mouse grey to mouse grey because of the formation of chlamydospores; reverse uncoloured to olivaceous grey.

Material examined: USA, Indiana, isolated from soil, unknown date, M.R. Tansey (holotype CBS H-23489, culture ex-type CBS 183.81).

Mycothermus thermophilus (Cooney & R. Emers.) X. Wei Wang, Houbraken & D. O. Natvig, comb. nov. MycoBank MB824454. Fig. 30.

Open in a separate window

Fig. 30

Mycothermus thermophilus (A–C: CBS 625.91, ex-type culture; D–F: CBS 626.91 ex-type of Humicola insolens; CBS 627.91 ex-type of Humicola grisea var. thermoides). A, D, G. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–C, E–F, H–I. Hyphae, and chlamydospores. Scale bars = 20 μm.

Basionym: Torula thermophila Cooney & R. Emers., Thermophilic Fungi: 92. 1964.

Synonyms: Scytalidium thermophilum (Cooney & R. Emers.) Austwick, New Zealand J. Agric. Res. 19: 29. 1976.

Mycothermus thermophilus (Cooney & R. Emers.) D.O. Natvig et al., Mycologia 107: 321. 2015, nom. inval. (Art. 42.1).

Humicola insolens Cooney & R. Emers., Thermophilic Fungi: 72. 1964.

Humicola grisea var. thermoides Cooney & R. Emers., Thermophilic Fungi: 72. 1964.

Micromorphology: Somatic hyphae hyaline, 1–6(–7) μm wide. Chlamydospores holothallic, thick-walled, brown, superficial or immersed, varying in morphology in different isolates, intercalary or lateral on the hyphae, or terminal on the short side branches of hyphae, solitary or in chains or in clusters, smooth, doliiform, globose, subglobose, oblong or obovoid, (5.5–)7–14(–22) × (4.5–)6–11 (–16) μm. Occasionally with spinose ornamentation.

Culture characteristics: Colonies on OA more than 70 mm diam in 7 d at 37 °C; edge entire or crenate; obverse smoke grey, buff to hazel because of the formation of chlamydospores, aerial mycelium sparse; reverse smoke grey or hazel. Colonies on CMA more than 70 mm diam in 7 d at 37 °C; edge entire or crenate; obverse smoke grey to greenish olivaceous or hazel because of the formation of chlamydospores, aerial mycelium sparse; reverse ochreous to cinnamon. Colonies on MEA more than 70 mm diam in 7 d at 37 °C; edge lobate, crenate or slightly fimbriate; aerial mycelium grey white, smoke grey, vinaceous buff or greyish sepia, texture floccose; reverse olivaceous buff to greenish olivaceous or isabelline. Colonies PCA more than 70 mm diam in 7 d at 37 °C; edge lobate or crenate; aerial mycelium sparse or absent; obverse colourless or pale mouse grey to mouse grey because of the formation of chlamydospores; reverse uncoloured to olivaceous grey.

Material examined: Switzerland, Zürich, Gossau, isolated from mushroom compost, 10 Apr. 1963, C.L. Fergus, culture CBS 226.63. USA, Nevada, isolated from chicken nest straw, 1950, D.G. Cooney, holotype of Torula thermophila, UC 1206525, culture ex-type CBS 625.91 = ATCC 16463; California, isolated from rotting guayule shrub, 1944, P.J. Allen, J, Naghski & S.R. Hoover, culture ex-type of Humicola insolens CBS 626.91 = ATCC 16454 = NBRC 107640; California, isolated from dung of elephant dung, 1948, D.G. Cooney, culture ex-type of Humicola grisea var. thermoidea CBS 627.91 = ATCC 16453; California, Berkeley, unknown substrate, unknown date, R.E. Smith, culture CBS 392.69.

Notes: The three isolates noted above were designated as types of three different taxa by Cooney & Emerson (1964). The ex-type culture CBS 625.91 of Torula thermophila has relatively thick vegetative hyphae, 1–7 μm wide. Its chlamydospores usually form from the swelling of the cells of superficial hyphae, appear intercalary in chains, doliiform, oblong or subglobose, (5.5–)7.5–12(–16) × (4.5–)6–9.5(–11) μm. CBS 626.91, the ex-type culture of Humicola insolens, produces similar hyphae, 1–6 μm wide. The chlamydospores are intercalary or lateral on superficial or immersed hyphae, solitary or in chains, globose, subglobose, doliiform, oblong or obovoid, (6–)7–14(–22) × (5.5–)7–11 (–16) μm. CBS 627.91, the ex-type culture of Humicola grisea var. thermoidea produces relatively thin hyphae, 1–4 μm wide. Its chlamydospores are usually produced laterally or terminally on short side branches of superficial or immersed hyphae, commonly solitary, globose, subglobose, or obovoid, (8–)9–11.5(–13) × (7–)8–10.5(–12) μm. Germ pores were observed on some spores of CBS 626.91 and CBS 627.91. Each isolate produces thick-walled cells intercalary within the hyphae, a common character.

 Natvig et al. (2015) noticed the close phylogenetic relationship of the ex-type cultures of Torula thermophila (basionym of Mycothermus thermophilus), Humicola insolens and Humicola grisea var. thermoides. In their description of My. thermophilus, they quoted the original description of Torula thermophila and did not incorporate the morphological diversity of the newly recognised My. thermophilus (as shown in Fig. 30).

Remersonia Samson & Seifert, Can. J. Bot. 75: 1160. 1997. MycoBank MB27809.

Type species: Remersonia thermophila (Fergus) Seifert & Samson.

Synonym: Synnmukerjiomyces K. R. Aneja & R. Kumar, Adv. Microbial Biotech. (in: J.P. Teware et al.): 2. 1999, nom. inval. Art. 37.1, fide Seifert et al. (2011), based on the protologue.

Notes: The type species of Remersonia was originally described as Stilbella thermophila (Fergus 1964). Stilbella is a typical synnematous hyphomycete with phialidic conidiogenous cells and slimy conidia, which is considered to be an anamorphic form in Bionectriaceae, Hypoceales (Seifert et al. 2011). Based on a detailed study of the type and supplementary isolates, Remersonia was proposed by Seifert et al. (1997) for this species. Remersonia is different from Stilbella in its thermotolerant growth and percurrently-extending conidiogenous cells. Their sequence data of 18S and 28S ribosomal DNA showed that this genus belonged to the Sordariales. The synonymous genus Synnmukerjiomyces was described two years after Remersonia, apparently based on the same species (as S. thermophilus “(Lindau)” K. R. Aneja & R. Kumar, apparently confusing the original author of the genus Stilbella Lindau as the author of the species epithet thermophila).

 The four Remersonia isolates studied here belong to two different species (Fig. 1, Fig. 2). Unfortunately, the ex-type culture of R. thermophila in the CBS collection is no longer viable. Natvig et al. (2015) showed, based on a phylogenetic analysis of a combined sequence dataset (ITS, tub2, mcm7, rpb1 and rpb2), that R. thermophila, represented by the ex-type, is a close relative of Mycothermus in the Chaetomiaceae. To supplement their data, we sequenced the the same fragement of tub2 for our four Remersonia isolates and six isolates of My. thermophilus, including the ex-type culture of My. thermophilus and two more representatives that were used in the study of Natvig et al. (2015). Three of our four isolates (Fig. 3) are conspecific with R. thermophila, and CBS 784.85 is a novel species which is described below. The close relationship between Remersonia and Mycothermus is also confirmed.

Remersonia tenuis X. Wei Wang, Houbraken & Seifert, sp. nov. MycoBank MB824456. Fig. 31.

Open in a separate window

Fig. 31

Remersonia tenuis (CBS 784.85). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B. Part of the colony on OA. C–D. Synnemata on OA. E–G. Synnemata mounted in lactic acid. H–I. Conidiogenous cells. J. Conidia. Scale bars: B = 500 μm; C–D = 200 μm; E–F = 50 μm; G = 20 μm; H–J = 10 μm.

Etymology: The epithet refers to the relatively narrow conidia of this species.

Micromorphology: Synnemata on OA 250–520 μm tall, scattered, sparse, often forming between two colonies, cylindrical and capitate, unbranched, slender, hyaline. Stipe 10–37 μm wide, smooth. Hyphae of stipe 1.5–2.5 μm wide, parallel and interweaving with each other through most of stipe. Conidiophores unbranched or branched once. Conidiogenous cells 13–110 μm long, 3–4.5 μm wide, proliferating percurrently and forming nodose annellations, 1–4.5 μm between annellations. Conidial mass measures (50–)100–400 μm in diam, slimy, hyaline to straw, globose to subglobose when wet, becoming dry and pyriform or fusiform in a few minutes, with columns of laterally adhered conidia tending to poke out of the conidial mass. Conidia (9.5–)11.5–16.5(–18.5) × (2.5–)3.5–4.5 (–5) μm, hyaline, oblong, clavate or ellipsoidal, sometimes slightly curved, with a truncate base and rounded apex.

Culture characteristics: Colonies on OA more than 70 mm diam in 7 d at 37 °C; edge entire; obverse uncoloured, occasionally fawn; aerial mycelium absent; reverse uncoloured. Colonies on CMA more than 70 mm diam in 7 d at 37 °C; edge entire; obverse uncoloured or olivaceous buff; aerial mycelium absent; reverse uncoloured. Colonies on MEA 37–43 mm diam in 7 d at 37 °C; edge entire; obverse olivaceous buff, with radiating furrows, producing numerous synnemata; reverse ochreous. Colonies on PCA more than 70 mm diam in 7 d at 37 °C; edge entire; aerial mycelium absent; reverse uncoloured.

Material examined: India, Hyderabad, isolated from dung of horse, unknown date, M.N. Rao (holotype CBS H-18610, culture ex-type CBS 784.85 = IMI 295313 = JCM 10546).

Notes: This species can be distinguished from R. thermophila by smaller conidia (11.5–16.5 × 3.5–4.5 μm vs 13–22.5 × 5–7 μm), and its faster growth rate at 37 °C (Table 2). Figs. 3–8 in Seifert et al. (1997) are the ex-type strain and thus represent R. tenuis rather than R. thermophila as labelled; the difference in conidial size and conidiophore branching is also evident from that figure.

Remersonia thermophila (Fergus) Seifert & Samson, Canad. J. Bot. 75: 1160. 1997. MycoBank MB437277. Fig. 32, Fig. 33, Fig. 34.

Open in a separate window

Fig. 32

Remersonia thermophila (CBS 540.69). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–C. Synnemata on OA, top view. D. Synnemata on OA, side view. E. Synnemata mounted in lactic acid. F. Conidiogenous cells. G. Conidia. Scale bars: B–C = 500 μm; D = 100 μm; E–G = 10 μm.

Open in a separate window

Fig. 33

Remersonia thermophila (CBS 643.91). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B. Part of the colony on OA. C–D. Synnemata on OA. E–G. Synnemata mounted in lactic acid. H. Parts of conidiophores and conidiogenous cells with conidia. I. Conidia. Scale bars: B = 500 μm; C, D = 200 μm; E–G = 50 μm; H–I = 10 μm.

Open in a separate window

Fig. 34

Remersonia thermophila (CBS 645.91). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B. Part of the colony on OA. C. Synnemata on OA, top view. D–E. Synnemata on OA, side view. F–H. Synnemata mounted in lactic acid. I. Conidiogenous cells. J. Conidia. Scale bars: B = 1000 μm; C, E = 200 μm; D = 100 μm; F–H = 20 μm; I–J = 10 μm.

Basionym: Stilbella thermophila Fergus, Mycologia 56: 277. 1964.

Micromorphology: Synnemata on OA 170–1 100 μm tall, scattered to gregarious, cylindrical to clavate, capitate, unbranched, hyaline, sometimes fulvous to sepia when old. Stipe 5–320 μm wide in the mid part, smooth. Hyphae of stipe 1.5–3.5 μm wide, parallel and interweaving with each other through most of stipe. Conidiophores unbranched or simply branched once to twice. Conidiogenous cells 14–90 μm long, 3.5–6.5 μm wide, proliferating percurrently and forming nodose annellations, 1.5–26.5 μm between annellations. Conidial mass 50–1 300 μm in diam, slimy, hyaline, straw or pure yellow, globose or subglobose when wet, becoming dry and pyriform or fusiform in a few minutes. Conidia (10.5–)13–22.5(–26.5) × (4.5–)5–7(–9) μm, hyaline, oblong, clavate or ellipsoidal, occasionally pyriform, sometimes slightly curved, with a truncate base and rounded apex.

Culture characteristics: Colonies on OA 36–55 mm diam in 7 d at 37 °C; edge entire to lobate or crenate; obverse smoke grey to vinaceous buff, or fawn to olivaceous, often with radiating furrows starting from the central point, sometimes forming several dark brick to sepia concentric and crenate rings; aerial mycelium absent; reverse uncoloured, straw, olivaceous buff, fawn or olivaceous. Colonies on CMA 26–39 mm diam in 7 d at 37 °C; edge entire, lobate or crenate; obverse fawn, or pale isabelline; aerial mycelium absent; reverse fawn, olivaceous or isabelline. Colonies on MEA 26–46 mm diam in 7 d at 37 °C; edge entire, lobate, crenate or fimbriate; obverse buff, fawn to vinaceous grey, producing numerous synnemata and often mixed with aerial hyphae; reverse uncoloured, or ochreous to cinnamon, or fulvous to umber. Colonies PCA 10–38 mm diam in 7 d at 37 °C; edge lobate, crenate or fimbriate; aerial mycelium absent; reverse buff or uncoloured.

Material examined: Netherlands, Horst, isolated from compost, Apr. 1987, G. Straatsma, culture CBS 643.91; Horst, isolated from compost, Jun. 1991, G. Straatsma, culture CBS 645.91. Switzerland, Gossau-Zürich, isolated from mushroom compost during peak heating, 1962, C.L. Fergus, culture CBS 540.69 = MUCL 15081.

Notes: This species exhibit a high morphological diversity in colony characters, synnemata, conidiophores and conidiogenous cells, but conidial size and shape are consistent between different isolates (Fig. 32, Fig. 33, Fig. 34, Table 2).

Staphylotrichum J.A. Mey. & Nicot, Bull. Soc. Mycol. France 72: 322. 1957. MycoBank MB10065.

Type species: Staphylotrichum coccosporum J.A. Mey. & Nicot.

Micromorphology: Asexual morphs usually of two types: type one macronematous, possessing conidiophores arising from an intercalary, thick-walled, pigmented foot cell, usually pigmented and thick-walled in the lower part, tapering and fading towards the tips, apically branched, with denticle-like conidiogenous cells terminally on the tops of the branches; type two micronematous, with cylindrical or denticle-like conidiogenous cells arising directly from hyphae rather than apical branches of macronematous conidiophores. Conidia holoblastic, solitary, single-celled, smooth or slightly verrucose, hyaline to pale brown, usually globose, subglobose or obovoid. Sexual morph absent or present. Ascomata superficial, or covered by aerial hyphae, ostiolate, elongate obpyriform, obclavate or ampulliform below, usually apically attenuated to a cylindrical, thread-like neck which is composed of fused basal part of the terminal hairs. Terminal hairs seta-like or whip-like, fused at the lower part to form a channel through which a column of ascospores emerges from the ascomata, smooth. Asci clavate to fusiform, with 8 irregularly-arranged ascospores, evanescent. Ascospores broad limoniform to nearly globose, often somewhat biapiculate, bilaterally flattened, with an apical germ pore.

Notes: Staphylotrichum is well known for its apically branched macronematous conidiophores (Fig. 58G–I). Our observations showed that micronematous formation of conidia on hyphae (Fig. 58F) is also a very common character in the asexual Staphylotrichum species. Eight Staphylotrichum isolates were selected for this study, including the ex-type strain of the type species, all originally deposited as S. coccosporum in CBS. In the rpb2 and four-locus phylograms, the “Chaetomium longicolleum” clade split the “S. coccosporum” clade into two separate subclades, indicating a close relationship between these sexual and asexual organisms. Production of micronematous, occasionally even macronematous asexual morphs in sexually reproducing species is additional morphological support that the “Chaetomium longiculleum” clade represents the sexual morph of Staphylotrichum. Fig. 43 shows the colony morphology of the asexual species in the genus.

Open in a separate window

Fig. 43

Diversity of colony morphology in Staphylotrichum. From left to right on OA, CMA, MEA and PCA. From top to bottom CBS 281.65 (S. acaciicola), CBS 554.89 (S. acaciicola); CBS 112543 (S. boninense); CBS 408.67 (S. brevistipitatum), CBS 294.55 (S. brevistipitatum); CBS 364.58 (S. coccosporum).

Open in a separate window

Fig. 58

Morphological differences in the asexual morph of Humicola, Staphylotrichum and Trichocladium. A–E. Humicola: Hyphae and conidia (A. Humicola distorta, ex-type CBS 417.66; B. H. fuscoatra, ex-type CBS 118.14; C. H. longistipe, ex-type CGMCC 3.13791; D. H. floriformis, ex-type CBS 815.97; E. Humicola fuscobrunnea ex-type CGMCC 3.13790). F–I. Staphylotrichum: Hyphae, conidiophores, conidiogenous cells and conidia (F. S. tortipilum, ex-type CBS 103.79; G. S. brevistipitatum, ex-type CBS 408.67; H–I. S. coccosporum, CBS 364.58). J–N. Trichocladium: Hyphae, conidiophores, conidiogenous cells and conidia (J. T. jilongense ex-type HSAUPII07 1485; K. T. griseum, ex-neotype CBS 119.14; L. T. gilmaniellae, ex-type CBS 388.75; M. T. nigrospermum, CBS 103.36; N. T. asperum, ex-epitype CBS 903.85). Scale bars: A–F, J–N = 10 μm; G–I = 20 μm.

Staphylotrichum acaciicola X. Wei Wang & Houbraken, sp. nov. MycoBank MB824457. Fig. 35.

Open in a separate window

Fig. 35

Staphylotrichum acaciicola (CBS 281.65, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 3 wk incubation. B–D. Conidiophores with macronematous conidia and hyphae with micronematous conidia. Scale bars = 20 μm.

Etymology: The epithet refers to Acacia karroo, the substrate from which the type strain was isolated.

Micromorphology: Somatic hyphae hyaline or subhyaline, producing macronematous conidia mixed with micronematous ones. Macronematous conidiophores arising from a thick-walled L-shaped or cylindrical, brown to dark brown foot cell, brown to dark brown and thick-walled in the lower part, tapering and fading towards the tips, 210–500(–800) μm long, 3–5(–6.5) μm wide near the base, apically branched. Conidiogenous cells hyaline, denticle-like to cylindrical, 2–13.5(–15) × 1–3 μm. Conidia pale olivaceous, smooth, single-celled, globose, subglobose or obovoid, (6.5–)7.5–11.5(–14.5) × (7–)7.5–10(–12.5) μm. Sexual morph not observed.

Culture characteristics: Variation in culture characteristics were observed among isolates (Fig. 43). Colonies on OA 50–56 mm diam after 7 d at 25 °C; edge entire; obverse pale olivaceous grey (CBS 281.65) or amber with sparse to dense aerial hyphae (CBS 554.89); reverse uncoloured to buff (CBS 281.65), or ochreous (CBS 554.89). Colonies on CMA 46–52 mm diam after 7 d at 25 °C; edge entire; obverse white to pale olivaceous grey (CBS 281.65) or amber with white to salmon aerial hyphae (CBS 554.89); reverse buff (CBS 281.65) or pale luteous (CBS 554.89). Colonies on MEA 49–55 mm diam after 7 d at 25 °C; edge entire; obverse floccose and white to buff white (CBS 281.65) or pale luteous because of aerial hyphae (CBS 554.89); reverse fulvous to sepia (CBS 281.65) or sienna (CBS 554.89). Colonies on PCA 48–54 mm diam after 7 d at 25 °C; edge entire; obverse transparent, buff and loosely fluccose because of the formation of conidiophores; aerial hyphae absent; reverse uncoloured.

Material examined: Brazil, isolated from rainforest soil, unknown date, L. Pfenning, culture CBS 554.89. South Africa, Potchefstroom, isolated from leaf litter of Acacia karroo, unknown date, M.C. Papendorf, (holotype CBS H-23490, culture ex-type CBS 281.65). USA, Kansas, isolated from soil, unknown date, M. Christensen, culture CBS 127289.

Notes: Staphylotrichum acaciicola is phylogenetically closely related to S. coccsporum. This species can be distinguished by the production of numerous conidia from micronematous conidiogenous cells on hyphae. In contrast, S. coccosporum predominantly produces macronematous conidiogenous cells on conidiophores. In addition, S. coccosporum produces relatively broad conidiophores in comparison to those of S. acaciicola (4.5–9 μm vs 3–6.5 μm near the base). The colony morphology of S. acaciicola varies among different isolates.

Staphylotrichum boninense Nonaka, Miyazaki & Masuma, Mycoscience 53: 315. 2012. MycoBank MB561191. Fig. 36.

Open in a separate window

Fig. 36

Staphylotrichum boninense (CBS 112059). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–E. Micronematous conidia arising from hyphae and a few conidiophores with macronematous conidia. F. Micronematous conidia arising from hyphae. Scale bars = 20 μm.

Micromorphology: Somatic hyphae hyaline or nearly so, producing macronematous conidia mixed with micronematous ones. Macronematous conidiophores arising from a thick-walled L-shaped or cylindrical, brown to dark brown foot cell, brown to dark brown and thick-walled in the lower part, tapering and fading towards the tips, 410–600(–800) μm long, 3.5–5(–7) μm wide near the base, apically branched. Conidiogenous cells hyaline, denticle-like to cylindrical, 2–13.5(–16) × 1.5–3 μm, sometimes intercalary in the hyphae. Conidia pale olivaceous, single-celled, smooth, globose, subglobose or obovoid, (5–)7–12(–14) μm diam. Sexual morph not observed.

Culture characteristics: Colonies on OA 36–42 mm diam after 7 d at 25 °C; edge entire; obverse vinaceous buff to fawn with sparse aerial hyphae; reverse buff. Colonies on CMA 36–42 mm diam after 7 d at 25 °C; edge entire; obverse fawn with greyish white to buff fluccose aerial hyphae; reverse uncoloured to buff. Colonies on MEA 41–47 mm diam after 7 d at 25 °C; edge entire; obverse ochreous and floccose because of the aerial hyphae, with an irregular mouse grey ring; reverse rust to bay caused by soluble pigments diffusing into the medium. Colonies on PCA 36–42 mm diam after 7 d at 25 °C; edge entire; obverse pale mouse grey, without aerial hyphae; reverse pale olivaceous grey to smoke grey.

Material examined: Brazil, Pista Cláudio Coutinho near Pão de Açúcar, isolated from twig, 12 Oct. 2002, R.F. Castaneda-Ruiz, culture CBS 112059; Pista Cláudio Coutinho near Pão de Açúcar, isolated from leaf litter, 12 Oct. 2005, A. Stchigel & J. Guarro, CBS 112543.

Notes: The two examined S. boninense strains share identical ITS and LSU sequences with the type of S. boninense. Their morphology also fits the original description of S. boninense, and they are therefore identified here as that species. Staphylotrichum boninense is morphologically similar to S. acaciicola. On OA and CMA, micronematously-produced conidia from hyphae are often predominant. Phylogenetically, S. boninense and S. brevistipitatum are more closely related to the sexual species (S. longicolleum, S. microascosporum, S. tortipilum) than to S. acaciicola and S. coccsporum (Fig. 1).

Staphylotrichum brevistipitatum X. Wei Wang & Houbraken, sp. nov. MycoBank MB824458. Fig. 37.

Open in a separate window

Fig. 37

Staphylotrichum brevistipitatum (CBS 408.67, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–D. hyphae and micronematous conidia. E–H. Conidiophores with macronematous conidia and hyphae with micronematous conidia. Scale bars: B–D = 10 μm; E–H = 20 μm.

Etymology: The epithet refers to the short conidiophores of this fungus.

Micromorphology: Somatic hyphae hyaline or nearly so, producing macronematous conidia mixed with micronematous ones. Macronematous conidiophores arising from a thick-walled T-shaped to oblong and brown to dark brown foot cell, brown to dark brown and thick-walled in the lower part, tapering and fading towards the tips, 70–230 μm long, 2.5–5 μm wide near the base, apically branched. Conidiogenous cells hyaline, denticle-like to cylindrical, 3–11.5(–19) × 1.5–3 μm. Conidia olivaceous, single-celled, smooth to slightly verrucose, globose, subglobose, obovoid or pyriform, (8.5–)9.5–12(–14.5) × (7.5–)9–11.5(–13.5) μm. Sexual morph not observed.

Culture characteristics: Variations of culture characteristics were observed among isolates. Colonies on OA 42–48 mm diam after 7 d at 25 °C; edge entire; obverse grey olivaceous and floccose because of aerial hyphae mixed with conidiophores (CBS 408.67) or greenish black without aerial hyphae (CBS 294.55); reverse greenish black. Colonies on CMA 42–48 mm diam after 7 d at 25 °C; edge entire; obverse floccose, greyish white to greyish yellow-green, grey olivaceous at the edge (CBS 408.67), or dark grey olivaceous without aerial hyphae (CBS 294.55); reverse olivaceous black. Colonies on MEA 49–55 mm diam after 7 d at 25 °C; edge entire; obverse floccose and smoke grey to greyish sepia (CBS 408.67), or dark mouse grey with grey mouse aerial hyphae (CBS 294.55); reverse fuscous (CBS 408.67) or chestnut to sepia (CBS 294.55). Colonies on PCA 40–46 mm diam after 7 d at 25 °C; edge entire; obverse transparent, greyish sepia without aerial hyphae; reverse smoke grey or greyish sepia.

Material examined: South Africa, Zoeloeland, Empangeni, isolated from leaf litter of Eucalyptus, unknown date, A. Eicker (holotype CBS H-18521, culture ex-type CBS 408.67). Zaire, isolated from soil, unknown date, J.A. Meyer, culture CBS 294.55.

Notes: Staphylotrichum brevistipitatum is phylogenetically closely related to S. boninense, but can be distinguished by the production of shorter seta-like conidiophores (70–230 μm vs 410–780 μm).

Staphylotrichum coccosporum J.A. Mey. & Nicot. Bull. Soc. Mycol. France 72: 323. 1957. MycoBank MB306413. Fig. 38.

Open in a separate window

Fig. 38

Staphylotrichum coccosporum (CBS 364.58, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–G. Macronematous conidia. Scale bars: B–G = 20 μm.

Micromorphology: Asexual morph predominantly producing conidia macronematously from seta-like conidiophores on OA and CMA. Somatic hyphae hyaline or nearly so. Macronematous conidiophores arising from a thick-walled L-shaped or T-shaped brown to dark brown foot cell, brown to dark brown and thick-walled in the lower part, tapering and fading towards the tips, 250–780 μm long, (3.5–)4.5–9 μm wide near the base, apically branched. Conidiogenous cells hyaline, denticle-like to cylindrical, 2–13 × 1.5–3 μm. Conidia pale olivaceous, single-celled, globose, subglobose, occasionally obovoid or pyriform, (7.5–)8.5–11.5(–13.5) × (7.5–)8–10(–11) μm. Sexual morph not observed.

Culture characteristics: Colonies on OA 39–45 mm diam after 7 d at 25 °C; edge entire; obverse smoke grey to greyish sepia, floccose because of the formation of numerous conidiophores; reverse uncoloured, buff or umber when old. Colonies on CMA similar to those on OA, 35–41 mm diam after 7 d at 25 °C. Colonies on MEA 43–49 mm diam after 7 d at 25 °C; edge entire; obverse buff and floccose; reverse ochreous to apricot. Colonies on PCA 42–48 mm diam after 7 d at 25 °C; edge entire; obverse transparent, without aerial hyphae; reverse uncoloured.

Material examined: Zaire, Yangambi, isolated from soil, unknown date, J.A. Meyer, culture ex-type CBS 364.58.

Notes: Although S. coccosporum predominantly produces conidia macronematously from conidiophores, especially on OA and CMA, the micronematously-produced conidia on hyphae are easy to observe in slides cultures prepared using the inclined coverslip method. Micronematously-produced conidia are common in both sexual and asexual species in Staphylotrichum.

Staphylotrichum longicolleum (Krzemien. & Badura) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824459. Fig. 39, Fig. 40.

Open in a separate window

Fig. 39

Staphylotrichum longicolleum (CBS 119.57). A. Colonies from left to right on OA, CMA, MEA and PCA after 5 wk incubation. B–D. Ascomata mounted in lactic acid. E. Part of the colony on OA showing mature ascomata from top view. F. Mature ascomata on OA, side view. G. Micronematous conidia arising from short sides of hyphae (denticales). H. Asci. I. Ascospores. Scale bars: B = 20 μm; C–D = 50 μm; G–I = 10 μm.

Open in a separate window

Fig. 40

Staphylotrichum longicolleum (CBS 100950). A. Colonies from left to right on OA, CMA, MEA and PCA after 5 wk incubation. B–C. Ascomata and macronematous conidiophores attached to neck and terminal hairs of ascomata mounted in lactic acid. D. A macronematous conidiophore and conidia. E. Micronematous conidia. F. Part of the colony on OA showing mature ascomata from top view. G. Mature ascomata on OA, side view. H. Asci. I. Ascospores. Scale bars: B = 100 μm; C = 20 μm; D, E, H, I = 10 μm.

Basionym: Chaetomium longicolleum Krzemien. & Badura, Acta Soc. Bot. Pol. 23: 748. 1954.

Synonyms: Chaetoceratostoma longirostre Farrow, Mycologia 47: 418. 1955.

Chaetomium longirostre (Farrow) L.M. Ames, Monograph Chaetomiaceae: 29. 1963.

Chaetoceratostoma longicolleum (Krzem. & Badura) Badura, Allionia 9: 181. 1964.

Farrowia longicollea (Krzemien. & Badura) D. Hawksw., Persoonia 8: 174. 1975.

Micromorphology: Ascomata superficial, often covered by aerial hyphae, ostiolate, leaden black in reflected light, elongate obpyriform, obclavate or ampulliform below, apically attenuated to a cylindrical, thread-like neck which is composed of fused basal part of the terminal hairs, 55–125 μm diam at the widest part, (300–)550–1 300 μm high till the neck excluding the top parts of terminal hairs where the hairs separate with each other, of which, the neck part usually (110–)200–1 100 μm high, 25–45 μm wide. Ascomatal wall brown, composed of angular cells or elongated to cylindrical cells at the neck part in surface view. Terminal hairs seta-like or whip-like, fused at the lower part to form a channel through which a column of ascospores emerge from the ascomata, smooth, brown, septate, 2.5–6 μm diam near the separating base, tapering and fading towards the tips. Lateral hairs very sparse, seta-like, tapering and fading towards the tips. Asci clavate to fusiform, with spore-bearing part 22.5–34 × 13–20 μm and stalks 6–16 μm long, with 8 irregularly-arranged ascospores, evanescent. Ascospores olivaceous brown when mature, broad limoniform to nearly globose, biapiculate, bilaterally flattened, 9–11 (–11.5) × (8–)8.5–10.5(–11) × (6–)6.5–7.5 μm, with an apical germ pore. Conidiogenous cell arising from the hyphae, denticle-like to cylindrical, hyaline, sometimes intercalary. Conidia globose or subglobose, sometimes broad obovoid or pyriform, smooth, hyaline, subhyaline to pale olivaceous, lateral or terminal on the hyphae or short branches of hyphae, occasionally on macronematous conidiophores, solitary, sometimes two in chain or a few in cluster, (7–)9–13.5(–14.5) μm diam.

Culture characteristics: Colonies on OA 44–53 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white, yellow, luteous or amber; soluble pigment saffron, salmon to vinaceous or brick; reverse colourless, or saffron, salmon, cinnamon. Colonies on CMA similar to those on OA, 40–50 mm diam after 7 d at 25 °C; but aerial mycelium relatively thick, producing more ascomata. Colonies on MEA 46–52 mm diam after 7 d at 25 °C; edge entire; non-sporulated, aerial mycelium white to saffron; texture floccose; soluble pigment absent, or vinaceous to brick along the edge; reverse saffron, apricot to violaceous black. Colonies on PCA 43–55 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse, white to honey or absent; soluble pigment rosy buff to rosy vinaceous or absent; reverse uncoloured or pale vinaceous.

Material examined: Madagascar, isolated from soil under Theobroma cacao and Piper nigrum, unknown date, G. Doguet, culture CBS 119.57. Jamaica, Ocho Rios, isolated from woodland soil, unknown date, A. Carter, culture CBS 562.80 = TRTC 45836. Panama, Barro Colorade Island, isolated from soil, 1952, W.M. Farrow, isotype of Chaetoceratostoma longirostre, New York Botanical Garden Specimen ID01050425. Venezuela, isolated from leaf litter, Nov. 1997, R. F. Castañeda, culture CBS 100950 = INIFAT C98/35.

Notes: Chaetomium longirostre was separated from C. longicolleum by its much longer ascomatal neck (<800 μm vs >1 000 μm) and a narrower spore exit channel (Ames 1963). The holotype of Ch. longicolleum seems to be lost. Hawksworth (1975) designated a slide from Krzemieniewska & Badura (BPI–A 121) as lectotype. This slide is unavailable for study. Hawksworth (1975) observed that the ascomatal neck varied considerably, even within a single isolate. Our examination confirmed Hawksworth’s observation that the ascomatal necks can be (110–)200–1 100 μm high and 20–45 μm wide. The size of ascospores and the width of terminal hairs near the base are diagnostic characters in this species. The holotype was originally collected in Poland. Epitypification of the species is deferred until a culture is reisolated from the type locality.

Staphylotrichum microascosporum X. Wei Wang & Houbraken, sp. nov. MycoBank MB824460. Fig. 41.

Open in a separate window

Fig. 41

Staphylotrichum microascosporum (CBS 184.79, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Micronematous conidia. C–D. Ascomata mounted in lactic acid. E. Part of the colony. F. Mature ascomata on OA, side view. G. Asci. H. Ascospores. Scale bars: C = 100 μm; D = 20 μm; B, G–H = 10 μm.

Etymology: The epithet refers to the small ascospores of this species.

Micromorphology: Ascomata superficial, ostiolate, often covered by aerial hyphae, leaden black in reflected light, elongate obpyriform, obclavate or ampulliform below, apically attenuated to a cylindrical, thread-like neck which is composed of fused basal part of the terminal hairs, 65–110 μm diam at the widest part, (340–)430–760 μm high till the neck excluding the top parts of terminal hairs where the hairs separate with each other, of which, the neck part usually (170–)230–600 μm high, 18–28 μm wide. Ascomatal wall brown, composed of angular cells or elongated to cylindrical cells at the neck part in surface view. Terminal hairs seta-like or whip-like, fused at the lower part to form a channel through which a column of ascospores emerge from the ascomata, smooth, brown, septate, (3–)4.5–6.5 μm diam near the separated base, tapering and fading towards the tips. Lateral hairs very sparse, seta-like, tapering and fading towards the tips. Asci clavate to fusiform, with spore-bearing part 22–29 × 13–18.5 μm and stalks 6–18 μm long, with 8 irregularly-arranged ascospores, evanescent. Ascospores olivaceous brown when mature, broad limoniform to nearly globose, biapiculate, bilaterally flattened, 8–9.5 (–10) × 7.5–9 × 6–7 μm, with an apical germ pore. Conidiogenous cell arising from the hyphae, denticle-like to cylindrical, hyaline, sometimes intercalary. Conidia globose, subglobose, sometimes broad obovoid or pyriform, hyaline, subhyaline to pale olivaceous, lateral or terminal on the hyphae or short branches of hyphae, solitary, 8–13.5 μm diam.

Culture characteristics: Colonies on OA 31–37 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse, pale luteous or white; soluble pigment ochreous; reverse ochreous to fulvous. Colonies on CMA similar to those on OA, 29–35 mm diam after 7 d at 25 °C. Colonies on MEA 28–34 mm diam after 7 d at 25 °C; edge crenate; non-sporulated; aerial mycelium ochreous, sometimes white or salmon; texture floccose; reverse apricot caused by soluble pigment. Colonies on PCA 26–32 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse, ochreous; soluble pigment absent; reverse uncoloured.

Material examined: Sudan, White Nile Island, isolated from soil from Mangifera orchard, unknown date, B.P.R. Vittal (holotype CBS H-12643, culture ex-type CBS 184.79).

Notes: Staphylotrichum microascosporum produces smaller ascospores than the other known Staphylotrichum species (8–9.5 × 7.5–9 × 6–7 μm vs 9–11 × 8.5–10.5 × 6.5–7.5 μm).

Staphylotrichum tortipilum X. Wei Wang & Houbraken, sp. nov. MycoBank MB824461. Fig. 42.

Open in a separate window

Fig. 42

Staphylotrichum tortipilum (CBS 103.79, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B. Ascomata mounted in lactic acid. C. Terminal ascomatal hairs. D. Part of the colony on OA showing mature ascomata in top view. E. Mature ascomata on OA, side view. F. Micronematous conidia. G. Asci. H. Ascospores. Scale bars: B = 100 μm; C = 20 μm; F–H = 10 μm.

Etymology: The epithet refers to the slightly twisted terminal hairs of this species.

Micromorphology: Ascomata superficial, ostiolate, leaden black in reflected light, elongate obpyriform, obclavate or ampulliform below, apically attenuated to a cylindrical, thread-like neck which is composed of fused basal part of the terminal hairs, (60–)85–140 μm diam at the widest part, 530–1 330 μm high till the neck excluding the top parts of terminal hairs where the hairs separate with each other, of which, the neck part usually 340–1 050 μm high, 22–36 μm wide. Ascomatal wall brown, composed of angular cells or elongated to cylindrical cells at the neck part in surface view. Terminal hairs seta-like or whip-like, fused at the lower part to form a channel through which a column of ascospores emerge from the ascomata, smooth, brown, septate, 4.5–8 μm diam near the separating base, often twisted in the lower part, tapering and fading towards the tips. Lateral hairs sparse, seta-like, tapering and fading towards the tips. Asci clavate to fusiform, with spore-bearing part 28–35 × 14.5–18.5 μm and stalks 6.5–14.5 μm long, with 8 irregularly-arranged ascospores, evanescent. Ascospores olivaceous brown when mature, broad limoniform to nearly globose, biapiculate, bilaterally flattened, 10–10.5 (–11) × (8.5–)9–10(–10.5) × 6.5–7.5(–8) μm, with an apical germ pore. Conidiogenous cell arising from the hyphae, denticle-like to cylindrical, hyaline, occasionally intercalary. Conidia globose, subglobose, sometimes broad obovoid or pyriform, hyaline, subhyaline to pale olivaceous, lateral or terminal on the hyphae or short branches of hyphae, solitary, (8.5–)10.5–14 μm diam, up to 16.5 μm long when pyriform.

Culture characteristics: Colonies on OA 37–43 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse, white to pale luteous or salmon; soluble pigment pale luteous to ochreous; reverse fulvous. Colonies on CMA similar to those on OA, 35–41 mm diam after 7 d at 25 °C; reverse fulvous, orange or apricot. Colonies on MEA 36–43 mm diam after 7 d at 25 °C; edge crenate; non-sporulated; aerial mycelium thick, white to salmon; texture floccose; reverse rust to chestnut caused by soluble pigment. Colonies on PCA 31–37 mm diam after 7 d at 25 °C; edge entire; aerial mycelium rare; soluble pigment absent; reverse uncoloured.

Material examined: USA, North Carolina, isolated from dung of Pine vole, 20 Jul. 1976, G.L. Benny (holotype CBS H-12642, culture ex-type CBS 103.79).

Notes: Staphylotrichum tortipilum can be distinguished from S. longicolleum and S. microascosporum by larger ascomata (85–140 μm vs 55–125 μm diam at the widest part) and broader terminal hairs (4.5–8 μm vs 2.5–6.5 μm diam near the separated base), which are often twisted in the lower part.

Trichocladium Harz. Bull. Soc. Imp. Naturalistes. Moscou 44: 125. 1871. MycoBank MB10278.

Lectotype species: Trichocladium asperum Harz, fide Clements & Shear (1931)

Micromorphology: Asexual morphs diverse, with conidia from hyaline to pigmented on differentiated conidiophores or from conidiogenous cells, sometimes with acremonium-like conidia, or with hyaline micro-sclerotia, or absent. Ascomata superficial or immersed in the thick mycelium, ostiolate to nonostiolate. Asci typically cylindrical with 8 (4) uniseriate ascospores, sometimes clavate to fusiform with 8 biseriate ascospores, evanescent. Ascospores typically broadly ovate, bilaterally flattened, sometimes ellipsoidal and non-flattened, with an apical germ pore.

Notes: In a synopsis of the hyphomycete concept of Trichocladium (Goh & Hyde 1999), 18 species were accepted on the basis of morphological characters. Although the type specimens of only three species were available for our study, two (T. ismailiense, T. pyriforme) proved to be outside the Chaetomiaceae (data not shown).

 Trichocladium is morphologically diverse as phylogenetically delimited here (Fig. 1, Fig. 2), including four closely related subclades, each encompassing a high diversity in morphology. Subclade 1 includes the lectotype species T. asperum, which produces pigmented, solitary, monoblastic (1–) 2 (– multi-celled) conidia on somewhat differentiated conidiophores, and conidial secession is easily observed in old cultures. Subclades 2 and 3 only contain sexual species that produce ostiolate ascomata, such as Trichocladium crispatum (= Chaetomium crispatum), T. acropullum (= Chaetomium acropullum) or non-ostiolate ascomata, such as T. antarcticum (= Thielavia antarctica) and T. arxii (= Chaetomidium arxii). Species in subclade 4 produce hyaline asexual structures (conidia), like those produced by T. beniowskiae (= Beniowskia macrospora), or only poorly differentiated structures, such as those of T. amorphum. Sexual stages are present (e.g. T. seminis-citrulli) or absent in subclade 4.

 In the dual nomenclature era, Trichocladium was used for strictly asexually reproducing hyphomycetes. Here, six new combinations are proposed based on sexually reproducing species (previously classified in Chaetomidium, Chaetomium, Thielavia). Five asexually reproducing species were originally described in other genera (Beniowskia, Gilmaniella, Humicola, Monodictys) and those species lack typical trichocladium-like conidiophores and conidia. It is unlikely that these sexually reproducing species and the species described in the genera mentioned above would have earlier described names in Trichocladium itself. The new Trichocladium species described here produce thick-walled intercalary cells and microsclerotia-like structures. These structures are also atypical for Trichocladium.

Trichocladium acropullum (X. Wei Wang) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824462. Fig. 44.

Open in a separate window

Fig. 44

Trichocladium acropullum (CBS 114580, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 6 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–G. Ascomata mounted in lactic acid. H. Hyphae and chlamydospore-like structures on hyphae. I. Structure of ascomatal wall in surface view. J. Terminal ascomatal hairs. K. Asci. L. Ascospores. Scale bars: E–G = 50 μm; H–L = 10 μm.

Basionym: Chaetomium acropullum X. Wei Wang, Nova Hedwigia 80: 414. 2005.

Micromorphology: Ascomata superficial, sometimes covered by sparse aerial hyphae, nearly spherical to oblate, ostiolate, 170–260 μm high, 150–280 μm diam. Ascomatal wall around the apical ostiolar pore composed of angular and thick-walled dark brown cells, in the lower part dextrinoid, translucent and pale yellowish brown, cellular structure indistinct at first, then becoming yellowish brown to brown, with angular or irregular cells (textura angularis) when mature. Terminal hairs arising around the ostiole, regularly spirally coiled with flexuous lower part, punctulate or verrucose, 3–4.5 μm diam near the base. Lateral hairs seta-like or flexuous, tapering and fading towards the tips. Asci cylindrical, with spore-bearing part 36–49 × 6–7 μm and stalks 8.5–19 μm long, with 8 uniseriate ascospores, evanescent. Ascospores olivaceous to olivaceous brown when mature, subglobose to ellipsoidal, or ovate in face view, bilaterally flattened, (5.5–)6–7.5(–10) × (5–)5.5–6.5(–7) × 4–5(–5.5) μm, with an apical and often slightly protuberant germ pore. Conidia formed laterally or apically on substrate hyphae, hyaline to subhyaline, clavate, ovate, subglobose or irregularly shaped, often two or more in chains, 5–17 × 3–6(–7.5) μm.

Culture characteristics: Colonies on OA 26–32 mm diam after 7 d at 25 °C; edge entire; aerial mycelium thin or thick, white, irregularly distributed; texture cottony; soluble pigment absent; reverse uncoloured. Colonies on CMA similar to those on OA, 26–32 mm diam after 7 d at 25 °C. Colonies on MEA 24–30 mm diam after 7 d at 25 °C; edge lobate; non-sporulating; aerial mycelium thick, white to sulphur yellow; texture floccose; soluble pigment absent; reverse uncoloured. PCA 24–30 mm diam after 7 d at 25 °C; edge entire or slightly crenate, aerial mycelium sparse; soluble pigment absent; reverse uncoloured.

Material examined: China, Hubei, Shennongjia, isolated from garden soil, June 2003, X.W. Wang, ex-type culture CBS 114580. Iran, East Azerbaijan Prov., Bostanabad, isolated from leaf of Hordeum vulgare, 4 Jun. 2005, B. Asgari, culture CBS 126783.

Notes: The asexual structures of this species are similar to those observed in the cultures of T. seminis-citrulli (= Chaetomium seminis-citrulli) and T. amorphum (see below), supporting their close relationships.

Trichocladium amorphum X. Wei Wang & Houbraken, sp. nov. MycoBank MB824463. Fig. 45.

Open in a separate window

Fig. 45

Trichocladium amorphum (CBS 127763, ex-neotype culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–E. Hyphae, and the developmental changes of conidiophores and asexual structures on hyphae from young (B) to relatively old (E). Scale bars = 20 μm.

Etymology: The epithet reflects the poorly differentiated asexual structure of this species.

Micromorphology: Somatic hyphae hyaline, 1.5–6 μm wide. Asexual structures appearing cylindrical arthroconidia or swollen chlamydospores at the earlier stage, intercalary in hyphae, composed of hyaline, thick-walled cells, which can be solitary or in pairs or chains, later appearing several subglobose cells in clusters, or a mass of subglobose to angular cells like a hyaline microsclerotium, with the cells 6–25 × 2–6 μm when cylindrical, 4.5–11 μm diam when subglobose to angular. Sexual morph not observed.

Culture characteristics: Colonies on OA 47–53 mm diam after 7 d at 25 °C; edge entire; with aerial mycelium thin and white; texture loosely floccose; soluble pigment absent; reverse uncoloured. Colonies on CMA similar to those on OA, 45–51 mm diam after 7 d at 25 °C. Colonies on MEA 44–50 mm diam after 7 d at 25 °C; edge entire; aerial mycelium relatively thick, white; texture floccose; soluble pigment absent; reverse uncoloured. Colonies on PCA 41–47 mm diam after 7 d at 25 °C; edge entire; aerial mycelium thin or absent; soluble pigment absent; reverse uncoloured.

Material examined: USA, Laramie, Wyoming, isolated from greenhouse soil, unknown date, M. Christensen (holotype CBS H-23491, culture ex-type CBS 127763).

Notes: The ex-type culture was deposited as Sporendonema sp. in CBS, and the investigated culture could represent a contaminant of the original specimen. Trichocladium seminis-citrulli and T. amorphum produce similar asexual structures. The close relationship of these two species is also supported by the four-gene phylogeny. The poor development of the structures in the cultures of these two species could reflect unmet nutritional requirements in the media employed.

Trichocladium antarcticum (Stchigel & Guarro) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824464. Fig. 46.

Open in a separate window

Fig. 46

Trichocladium antarcticum (FMR 7920 = CBS 123565, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B. Part of the colony. C. Mature ascomata immersed in mycelium on OA, top view. D. Conidiophores and conidia. E–G. Ascomata mounted in lactic acid. H. A ruptured young ascoma, showing ascomatal wall structure in surface view and masses of asci flooding from the rupture. I. Asci. J. Ascospores. Scale bars: D, I, J = 10 μm; E = 50 μm; F–H = 20 μm.

Basionym: Thielavia antarctica Stchigel & Guarro, Mycologia 95: 1225. 2003.

Micromorphology: Ascomata superficial, often immersed in thick aerial mycelium, solitary to aggregated, non-ostiolate, glabrous, dark brown, globose, 150–360 μm diam. Ascomatal wall textura epidermoidea to intrincata. Asci numerous, cylindrical to elongate clavate, with spore-bearing part 25–51 × 8.5–16.5 μm, without conspicuous stalks, with 8 uniseriate or biseriate ascospores. Ascospores brown, broadly ovoid, bilaterally flattened, (7.5)8–9.5(10.5) × 7–9(10) × 4.5–6.5 μm, with an apical germ pore at the attenuated end. Acremonium-like conidiophores arising laterally or terminally from aerial hyphae, unbranched or simply branched, hyaline, aseptate or septate, 4–31 × 2–4.5 μm, with phialidic conidiogenous cells. Conidia in false heads or in basipetal chains, one-celled, smooth, obovoid, usually with a truncated base and a rounded apex, 2.5–4.5 × 2–3.5 μm.

Culture characteristics: Colonies on OA 30–36 mm diam after 7 d at 25 °C; edge lobate; with thick and white aerial mycelium; texture floccose; soluble pigment absent; reverse uncoloured. Colonies on CMA similar to those on OA, 30–36 mm diam after 7 d at 25 °C. Colonies on MEA 31–37 mm diam after 7 d at 25 °C; edge lobate; with thick aerial mycelium; white or yellowish white; texture floccose; reverse luteous to saffron. Colonies on PCA 27–33 mm diam after 7 d at 25 °C; edge undulate or lobate; aerial mycelium thin or absent; soluble pigment absent; reverse uncoloured.

Material examined: Antarctica, isolated from Usnea cf. aurantio-atra, Nov. 1996, A.M. Stchigel, culture ex-type CBS 123565 = FMR 7920; CBS 135876 = FMR 7290.

Notes: The cultures of T. antarcticum remained sterile at 25 °C in dark. Incubation of the culture near the window at a temperature around 20 °C and a day-night rhythm induced sporulation. When compared to the original description (Stchigel et al. 2003), the size of ascomata (150–360 μm vs 250–450 μm diam) and ascospores (8–9.5 × 7–9 × 4.5–6.5 μm vs 9–11 × 8–10 ×6.5–7 μm) of the ex-type were slightly smaller in this study. In the original publication, cylindrical asci with uniseriate ascospores were described; however, we observed elongate clavate or broad cylindrical asci with biseriate ascospores as well (Fig. 46I). All the other morphological characters fit with the original description. This species was described in Thielavia, but phylogenetic analysis clearly showed that it belongs to Trichocladium.

Trichocladium arxii (Benny) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824465. Fig. 47.

Open in a separate window

Fig. 47

Trichocladium arxii (CBS 104.79, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 4 wk incubation. B–C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Part of a terminal ascomatal hair together with two ascospores. H. Asci. I. Ascospores. Scale bars: E–F = 100 μm; G–I = 10 μm.

Basionym: Chaetomidium arxii Benny, Mycologia 80: 832, 1980.

Micromorphology: Ascomata superficial, non-ostiolate, greenish black, with numerous grey olivaceous to olivaceous grey ascomatal hairs in reflected light, spherical or nearly so, 130–230 μm diam. Ascomata walls consisting of cephalothecoid plates which are composed of radially elongated cells and surrounded by lines of dehiscence in surface view. Ascomatal hairs dark brown, seta-like and covering the whole ascomata, smooth, 2.5–4 μm near the base. Asci clavate or fusiform, with spore-bearing part 34–50 × 18–20.5 μm and stalks 10.5–25 μm long, with 8 biseriate ascospores, evanescent. Ascospores olivaceous brown when mature, ellipsoidal, (10.5–)12.5–14(–17) × (8–)9–11(–12) μm, with an apical germ pore. Asexual morph not observed.

Culture characteristics: Colonies on OA 36–42 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; soluble pigment buff to pale luteous; reverse buff to pale luteous. Colonies on CMA 36–42 mm diam after 7 d at 25 °C; edge entire; aerial mycelium sparse; soluble pigment pale luteous; reverse pale luteous. Colonies on MEA 29–35 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white; texture floccose; reverse apricot to sienna. Colony growth on PCA 34–40 mm diam after 7 d at 25 °C; edge entire, aerial mycelium absent; soluble pigment absent; reverse uncoloured.

Material examined: USA, California, isolated from dung of kangaroo rat, 29 Jul. 1974, G.L. Benny, ex-type CBS 104.79.

Notes: The genus Chaetomidium was synonymised with Chaetomium, and three Chaetomidium species were transferred to Chaetomium, including the type species C. fimeti (Wang et al. 2016a). In the study of Hernández-Restrepo (2017), Chaetomidium arxii clustered with Trichocladium asperum in their LSU tree. This is confirmed in our study using a larger data set. The phylogenetic placement of T. arxii in Trichocladium confirmed the polyphyly of the traditional “Chaetomidium” first shown by Greif et al. (2009). More study is needed to determine the phylogenetic relationships of the other “Chaetomidium” species.

Trichocladium asperum Harz, Bull. Soc. Imp. Naturalistes. Moscou 44: 125. 1871. MycoBank MB171452. Fig. 48, Fig. 49.

Open in a separate window

Fig. 48

Trichocladium asperum. Illustrated by Harz (1871, Bull. Soc. Imp. Moscow 44: Tab II Fig. 1), selected as a lectotype in this study.

Open in a separate window

Fig. 49

Trichocladium asperum (CBS 903.85, ex-epitype culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B–F. Hyphae, conidiophores and conidia. Scale bars = 10 μm.

Synonyms: Sporidesmium asperum Corda, Icon. fung. 2: 6. 1838.

Dicoccum asperum (Corda) Sacc., Syll. fung. 4: 342. 1886.

Monodictys aspera (Corda) S. Hughes, Canad. J. Bot. 36: 785. 1958.

Piricauda aspera (Corda) R.T. Moore, Rhodora 61: 96. 1959.

Micromorphology: Somatic hyphae hyaline, 1.5–3.5 μm wide. Conidiophores hyaline, originating laterally or terminally from the hyphae, cylindrical, unbranched or branched 1–2 times, sometimes verticillate, 2–4.5 μm wide, up to 21.5 μm long, sometimes reduced to intercalary conidiogenous loci in the hyphae. Conidia solitary, 1- to 2-celled, occasionally 3-celled, usually with germ pore in each cell, obovate, pyriform, ellipsoid, constricted at the septa, conspicuously warted, (10.5–)14–21.5(–26) × (9–)10–19.5(–20) μm, olivaceous brown to dark brown, sometimes with a basal cell paler than the others, seceding from the mycelium when manure usually together with a part of conidiogenous cell.

Culture characteristics: Colonies on OA 43–49 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous black, with grey white to smoke grey, sparse floccose aerial hyphae; reverse olivaceous grey to greenish black. Colonies on CMA similar to those on OA similar, 41–53 mm diam after 7 d at 25 °C; reverse buff to pale luteous. Colonies on MEA 47–42 mm diam after 7 d at 25 °C; edge entire; obverse iron grey; aerial mycelium sparse, pale mouse grey; texture floccose; reverse cinnamon. Colonies on PCA 44–50 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous grey to iron grey; aerial mycelium sparse, pale mouse grey; reverse olivaceous grey to dark mouse grey.

Material examined: Lectotype re-designated here: tab II Fig. 1 illustrated by Harz in Bull. Soc. Imp. Moscow 44, 1871, reproduced here as Fig. 48. MBT 380604. Belgium, Kontich, isolated from agricultural soil, 28 Jan. 1964, G.L. Hennebert, culture CBS 112.67 = MUCL 6092. Germany, Edersee, Nieder-Werbe, isolated from acidic soil, unknown date, E. Falk, ex-epitype culture CBS 903.85. The Netherlands, unknown substrate, unknown date, C.M. Berkhout, culture CBS 140.21. Unknown country, unknown substrate, unknown date, O. da Fonseca, culture CBS 157.22.

Notes: In 1871, Harz published the generic name Trichocladium for three species, but did not designate the type species for the genus. In 1931, Clements & Shear lectotypified Trichocladium asperum as the type species of Trichocladium (followed by Hughes 1952). The descriptions of T. asperum Harz and Sporidesmium asperum Corda are based on different specimens, and the latter should therefore not be regarded as the basionym of T. asperum. For this reason, an illustration in the protologue of Trichocladium asperum Harz is reproduced and re-designated here as the lectotype of T. asperum (Fig. 47). This lectotype replaces the lectotype designated in error by Hernández-Restrepo et al. (2017), which is based on the illustration of Sporidesmium asperum Corda (MBT375510).

 Hambleton et al. (2005) found that ITS sequences of Humicola grisea and Trichocladium asperum were identical. In a phylogram based on LSU sequences, Humicola grisea clustered together with Trichocladium asperum (Hernández-Restrepo et al. 2017). This study confirms the close relationship between T. griseum (=H. grisea) and T. asperum; however, they are regarded as separate species based on their distinct morphology and differences in other genes.

Trichocladium beniowskiae (M.D. Mehrotra) X. Wei Wang & Houbraken, nom. nov. MycoBank MB824466. Fig. 50.

Open in a separate window

Fig. 50

Trichocladium beniowskiae (CBS 757.74, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–E. Hyphae, conidiophores, conidiogenous cells and developing conidia. F–G. Hyphae, conidiophores and mature conidia. Scale bars = 20 μm.

Basionym: Beniowskia macrospora M.D. Mehrotra, Sydowia 17: 149. 1964.

Etymology: The epithet refers to the genus Beniowskia, from which the species is transferred.

Micromorphology: Somatic hyphae hyaline, 2–6 μm wide. Conidiophores hyaline, originating laterally or terminally from the hyphae, hypha-like in the lower part, often consisting of swollen cells in chains or branched chains in the upper part, 2–5 μm wide near the base, up to 220 μm long, with the top swollen conidiogenous cells 5–10 μm wide. Conidia solitary to in short chains, single-celled, smooth, hyaline, globose or subglobose, (10–)14–20.5(–29.5) μm diam.

Culture characteristics: Colonies on OA 56–62 mm diam after 7 d at 25 °C; edge entire; obverse luteous to orange caused by soluble pigment; aerial mycelium white, irregularly distributing; texture floccose; reverse pale luteous to saffron. Colonies on CMA similar to those on OA, 56–62 mm diam after 7 d at 25 °C. Colonies on MEA 61–67 mm diam after 7 d at 25 °C; edge entire; aerial mycelium white, texture floccose; reverse luteous to orange. Colonies on PCA 47–53 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; reverse uncoloured.

Material examined: India, isolated from dried leaves of an unidentified grass, unknown date, M.D. Mehrotra, ex-type culture, CBS 757.74 = IMI 099625.

Notes: The type species of Beniowskia, B. sphaeroidea, is a grass pathogen that produces monoblastic conidia on sporodochia (Hanlin 1987) ornamented with coiled hyphae. Beniowskia macrospora (=Trichocladium beniowskiae) differs from B. sphaeroidea by the absence of coiled ornamenting hyphae on its sporodochia, the pattern of conidiophore branching, and its larger conidia (Mehrotra 1964). Although considered a synonym of B. sphaeroidea (Index Fungorum; http://www.indexfungorum.org, Aug. 2015), the differences in morphological characters make this unlikely. Hanlin (1987) noted that his attempts to culture B. sphaeroidea failed, in contrast to the ability of B. macrospora to grow in vitro. In our examination of CBS 757.74, no sporodochia were observed on any of the four media. Phylogenetic analyses clearly indicated that B. macrospora is a member of the Trichocladium lineage, but it remains uncertain whether this species is actually congeneric with the type of Beniowskia. Unfortunately, no type material of B. sphaeroidea was available for study and the phylogenetic position of the genus Beniowskia remains unknown. The name Trichocladium macrospora already exists, and therefore a new species epithet is required.

Trichocladium crispatum (Fuckel) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824467. Fig. 51, Fig. 52.

Open in a separate window

Fig. 51

Trichocladium crispatum. Holotype and illustration no. 2022 made by Fuckel, kept in Conservatoire et Jardin botaniques de la Ville de Genève, Switzerland.

Open in a separate window

Fig. 52

Trichocladium crispatum (CBS 149.58, ex-epitype culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 5 wk incubation. B. Part of the colony. C. A mature ascoma on OA, top view. D. A mature ascoma on OA, side view. E–F. Ascomata mounted in lactic acid. G. Structure of ascomatal wall in surface view. H. Lower part of a terminal ascomatal hair. I. Upper part of a terminal ascomatal hair. J. Asci. K. Ascospores. Scale bars: E–F = 100 μm; G–K = 10 μm.

Basionym: Sphaeria crispata Fuckel, Fungi Rhenani no. 2022. 1867.

Synonym: Chaetomium crispatum Fuckel, Symb. Mycol. P. 90. 1870.

Micromorphology: Ascomata superficial on the aerial myceliim, mouse grey in reflected light because of the ascomatal hairs, nearly spherical to ovoid, ostiolate, 150–320 μm high, 140–280 μm diam. Ascomatal wall brown, composed of angular to irregular cells in surface view. Terminal hairs arising around the ostiole, regularly spirally coiled with circinate to coiled apex and straight to flexuous lower part, occasionally with coiled branches, strongly verrucose or warty, 3–4.5 μm diam near the base, 5–8 μm diam in the coiled part. Lateral hairs seta-like or flexuous, tapering and fading towards the tips. Asci cylindrical, with spore-bearing part 52–66 × 6.5–9.5 μm and stalks 18–31 μm long, with 8 uniseriate ascospores, evanescent. Ascospores olivaceous to olivaceous brown when mature, broad ovate to limoniform in face view, often slightly biapiculate, bilaterally flattened, (8.5–)9–10(–11) × (7–)7.5–8.5 × 5–6.5 μm, with an apical germ pore at the attenuated end. Asexual morph not observed.

Culture characteristics: Colonies on OA 42–48 mm diam after 7 d at 25 °C; edge entire; obverse cottony, smoke grey to grey olivaceous; reverse greenish olivaceous because of the soluble citrine pigments diffusing into the medium. Colonies on CMA similar to those on OA, 42–48 mm diam after 7 d at 25 °C. Colonies on MEA 32–38 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous buff or smoke grey, cottony; reverse fuscous black. Colonies on PCA 35–41 mm diam after 7 d at 25 °C; edge entire; obverse smoke grey or olivaceous buff, loosely cotton; reverse grey olicaceous.

Material examined: The illustration no. 2022 was reproduced here as Fig. 51, which was made by Fuckel on the basis of the holotype of Chaetomium crispatum G00127921 (in Conservatoire et Jardin botaniques de la Ville de Genève, Switzerland) and kept together with the type specimen. Germany, isolated from estuarine sediment, unknown date, R. Siepmann, MBT381346 (epitype designated here, CBS H-23492, culture ex-epitype CBS 149.58). Netherlands, Wageningen, isolated from agricultural soil, unknown date and collector, culture CBS 693.71.

Notes: To stabilise the use of this species name, we propose strain CBS 149.58 as the epitype of T. crispatum, which was collected in the same country as the holotype specimen. Morphological features of the epitype fit well with the type as reproduced in Fig. 51.

Trichocladium gilmaniellae (Moustafa) X. Wei Wang & Houbraken, nom. nov. MycoBank MB824468. Fig. 53.

Open in a separate window

Fig. 53

Trichocladium gilmaniellae (CBS 388.75, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B. Hyphae, conidiophores and conidia. C–E. Conidia. Scale bars = 10 μm.

Basionym: Gilmaniella macrospora Moustafa, Persoonia 8: 332. 1975.

Etymology: The epithet refers to the genus Gilmaniella, from which the species is transferred.

Micromorphology: Somatic hyphae usually hyaline, thin-walled, 2–4 μm wide, some becoming olivaceous brown and thick-walled when old, 3.5–5 μm wide, with conidia produced on the minimally differentiated conidiophores, on the top of hyphae or on the side of vegetative hyphae. Conidiophores hyaline to subhyaline, unbranched, cylindrical, or slightly swollen on the top, 2.5–120 μm long, 2–4 μm wide near top, sometimes lacking where the spores arising from an undifferentiated intercalary conidiogenous cell (a hyphal cell). Conidia single-celled, usually solitary, occasionally 2–3 in chains, olivaceous brown to dark olivaceous brown, smooth or slightly verruculose, globose or subglobose, sometimes ellipsoidal, occasionally pyriform, (8.5–)11–15.5(–22.5) μm diam, with a conspicuous apical, subapical or lateral germ pore which is usually 2–3.5 μm wide.

Culture characteristics: Colonies on OA 39–45 mm diam after 7 d at 25 °C; edge entire; obverse mouse grey to iron grey; aerial mycelium grey white to pale olivaceous grey; texture floccose; reverse pale olivaceous grey. Colonies on CMA 37–43 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous grey to iron grey; aerial mycelium grey white to pale olivaceous grey; texture floccose; reverse pale olivaceous grey. Colonies on MEA 40–46 mm diam after 7 d at 25 °C; edge entire or slightly undulate; aerial mycelium pale olivaceous grey to olivaceous grey; texture floccose; reverse dark mouse grey. Colonies on PCA 33–39 mm diam after 7 d at 25 °C; edge entire; obverse iron grey to greenish black, greyish sepia to olivaceous in the centre; aerial mycelium sparse, smoke grey; reverse iron grey.

Material examined: Kuwait, isolated from salt-marsh soil, 1973, A.F. Moustafa, culture ex-type CBS 388.75.

Notes: The genus Gilmaniella was considered incertae sedis in Pezizomycotina and characterized by somewhat differentiated conidiophores and aseptate, pigmented conidia with a conspicuous germ pore (Barron, 1964, Kirk et al., 2008). The type species G. humicola was described with simple to branched, often inflated conidiophores and having sympodial conidiogenous cells with denticles on which conidia arise (Barron 1964). Trichocladium gilmaniellae (= Gilmaniella macrospora) produces conidia on monoblastic conidiogenous cells or even on undifferentiated hyphal cells. Furthermore, the conidiogenous cells lack denticles. The species appears very similar to the classic morphological concept of Humicola grisea, although the ‘germ pores’ are more obvious. Phylogenetically, Trichocladium gilmaniellae resides in a clade with T. asperum. The type species of Gilmaniella, G. humicola, is not a member of the Chaetomiaceae (Fig. 1). The epithet macrospora is already occupied in Trichocladium, namely T. macrospora P.M. Kirk, and a new name is therefore proposed.

Trichocladium griseum (Traaen) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824469. Fig. 54.

Open in a separate window

Fig. 54

Trichocladium griseum (CBS 119.14, ex-neotype culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B, D, G. Hyphae, conidiophores, thick-walled conidia and acremonium-like synanamorph. C, E, F. Hyphae, conidiophores and aleurioconidia. H–I. Hyphae, conidiophores and conidia of acremonium-like synanamorph. Scale bars = 10 μm.

Basionym: Humicola grisea Traaen, Nytt Mag. Naturvidensk 52: 34. 1914.

Micromorphology: Two types of asexual spores are observed in the culture on OA. Somatic hyphae hyaline, 1.2–3 μm wide. Conidiophores hyaline or subhyaline, usually pale brown below spores, unbranched, cylindrical, or swelling on the top, 2.5–50 μm long, 2–5 μm wide near top, sometimes lacking where the spores arising from an undifferentiated intercalary conidiogenous cell (a hyphal cell). Conidia single-celled, solitary, sometimes 2(–4) in chains or a few in clusters, olivaceous brown to dark olivaceous brown, smooth or slightly verruculose, globose or subglobose, (8–)12–16.5(–18) μm high, (7.5–)12–16(–17.5) μm wide. Acremonium-like conidiophores phialidic, formed laterally from hyphae, hyaline, unbranched, 9–21 μm long, 2–2.5 μm wide near the base. Acremonium-like conidia formed basipetally in chains, aseptate, obovoid, ellipsoidal, with a truncated base and a rounded apex, 2.5–3.5 × 2–2.5 μm.

Culture characteristics: Colonies on OA 42–48 mm diam after 7 d at 25 °C; edge entire; aerial mycelium pale olivaceous grey to mouse grey; texture floccose; reverse greenish black because of the immersed conidia and soluble pigment. Colonies on CMA similar to those on OA, 39–45 mm diam after 7 d at 25 °C. Colonies on MEA 41–47 mm diam after 7 d at 25 °C; edge entire; aerial mycelium olivaceous grey; texture floccose; reverse greenish black because of the immersed conidia and soluble pigment. Colonies on PCA 37–43 mm diam after 7 d at 25 °C; edge entire; obverse greyish sepia, olivaceous to greenish black; aerial mycelium sparse, grey white; reverse olivaceous black.

Material examined: China, Jilin, isolated from soil, Oct. 2009, T.Y. Zhang, CGMCC 3.13888. Germany, unknown substrate, unknown date, H.W. Wollenweber, CBS 217.34. Norway, isolated from soil, 1914, A.E. Traaen, MBT381347 (designated here as neotype, CBS H-23493, ex-neotype culture CBS 119.14 = ATCC 22724 = IMI 075664 = MUCL 8008).

Notes: Strain CBS 119.14 is designated here as the neotype of H. grisea. This culture was deposited by A.E. Traaen, who also described H. grisea. Two cultures were deposited, CBS 119.14 and ex-type of H. fuscoatra, CBS 118.14. A.E. Traaen (1914) didn’t designate a type in his paper, and CBS 119.14 is the only extant culture of this species from the original author. Acremonium-like synanamorphs were observed in the culture of CBS 119.14, although this structure was not mentioned in the original description of H. grisea. The formation of an acremonium-like synanamorph is not a stable character and could explain the difference between the original description and our observations (Domsch et al. 2007).

Trichocladium heterothallicum (Yu Zhang & L. Cai) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824470.

Basionym: Chaetomium heterothallicum Yu Zhang & L. Cai, Fungal Biol. 121: 29. 2017.

Micromorphology: Fide Zhang et al. (2017a) Ascomata ostiolate, dark brown, immersed, covered by the aerial mycelium, spherical or nearly so, 160–260 μm diam. Ascomatal wall brown, composed of textura angularis or irregularis. Ascomatal hairs numerous, 4–5.5 μm wide near the base, slightly straight below, spirally coiled in the upper part, dark brown, unbranched, nearly smooth. Asci cylindrical, with 8 uniseriate ascospores, short-stalked, 60–75 × 7.5–9.5 μm. Ascospores light brown, globose or subglobose, 8.5–11 × 7–9 μm, without distinct germ pore. Heterothallic. Chlamydospores present, subhyaline, generally globose, 6–9 μm in diameter, produced in intercalary chains.

Culture characteristics: Fide Zhang et al. (2017a). Colonies up to 52 mm diam. on PDA after 6 d at 25 °C; aerial mycelium abundant, lanose, yellow; soluble pigment orange or absent; reverse yellowish or orange brown.

Notes: Comparison of the sequences from Zhang et al. (2017a) with our dataset revealed a close relationship with T. amorphum and the most closely related sexual species is T. seminis-citrulli (= Ch. seminis-citrulli). Trichocladium heterothallicum produces intercalary chlamydospores in chains or in clusters (Zhang et al. 2017a), as do T. amorphum and T. seminis-citrulli. Trichocladium heterothallicum produces cylindrical asci and subglobose ascospores; the asci of T. seminis-citrulli are clavate and the ascospores broad ovoid or broad pyriform (Fig. 55).

Open in a separate window

Fig. 55

Trichocladium jilongensis (HSAUP II ₀₇1485, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 1 wk incubation. B–I. Hyphae, conidiophores and conidia. Scale bars = 10 μm.

Trichocladium jilongense (Y.M. Wu & T.Y. Zhang) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824471. Fig. 55.

Basionym: Humicola jilongensis Y.M. Wu & T.Y. Zhang, Mycotaxon 121: 148. 2012.

Micromorphology: Somatic hyphae hyaline to brown, 1.5–3.5 μm wide. Conidiophores unbranched, septate with a hyaline and cylindrical basal cell, or aseptate pale brown, ellipsoidal to doliiform, sometimes reduced to intercalary conidiogenous loci in the hyphae, cylindrical, originating laterally or terminally from the hyphae, 0–9(–32) μm long. Conidiogenous cell pale brown, terminal on conidiophores or intercalary in hyphae, 3–6.5 μm diam. Conidia solitary, smooth, olivaceous brown, 1–2(–3) celled, globose, subglobose, obovate, ellipsoid, constricted at the septa, 10–28 × 9.5–15 μm.

Culture characteristics: Colonies on OA 31–37 mm diam after 7 d at 25 °C; edge entire; aerial mycelium thick, greyish white, forming 3–6 concentric and crenate rings; texture floccose; reverse cinnamon to dark brick. Colonies on CMA similar to those on OA, 31–37 mm diam after 7 d at 25 °C. Colonies on MEA 32–38 mm diam after 7 d at 25 °C; edge created; aerial mycelium pale vinaceous buff to smoke grey; texture cottony; reverse sepia to purple slate. Colonies on PCA 28–34 mm diam after 7 d at 25 °C; edge entire; aerial mycelium smoke grey to grey olivaceous; texture fluccose; reverse grey olivaceous.

Material examined: China, Tibet, isolated from mountain soil, Sept 2007, Y.M. Wu, culture ex-type HSAUP II ₀₇1485. Germany, isolated from straw-meal-amended field soil, 1984, G.J. Wirth & G. Wolf, culture CBS 195.87.

Notes: This species sometimes produces conidia laterally from conidiogenous loci that are intercalary in the hyphae, similar to what is observed in Humicola species. However, the somewhat differentiated conidiophores are easily observed in the culture.

Trichocladium nigrospermum (Schweinitz) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824472. Fig. 56.

Open in a separate window

Fig. 56

Trichocladium nigrospermum (CBS 103.36). A. Colonies from left to right on OA, CMA, MEA and PCA after 2 wk incubation. B–E. Hyphae, conidiophores and conidia. Scale bars = 10 μm.

Basionym: Acremonium nigrospermum Schweinitz, Trans. Amer. philos. Soc. 4: 283. 1832.

Synonyms: Monodictys nigrosperma (Schwein.) W. Gams Cephalosporium-artige Schimmelpilze: 214. 1971.

Micromorphology: Somatic hyphae hyaline, 1.5–4 μm wide. Conidiophores hyaline, cylindrical, unbranched, originating laterally or terminally from the hyphae, 2–3.5 μm wide, up to 18.5 μm long, sometimes reduced to intercalary conidiogenous loci in the hyphae. Conidia solitary, muriform, obovate, pyriform, ellipsoid, quadrangular or subglobose, constricted at the septa, (9–)13.5–19.5(–22.5) × (9–)12.5–17(–19) μm, olivaceous brown to dark brown, sometimes with a basal cell paler than the others.

Culture characteristics: Colonies on OA 36–42 mm diam after 7 d at 25 °C; edge entire; observe greenish black; aerial mycelium pale mouse grey, sparse; reverse greenish black. Colonies on CMA similar to those on OA, 33–39 mm diam after 7 d at 25 °C. Colonies on MEA 36–42 mm diam after 7 d at 25 °C; edge entire; obverse iron grey; aerial mycelium pale mouse grey, sparse; reverse dark mouse grey to violaceous black. Colonies on PCA 32–38 mm diam after 7 d at 25 °C; edge entire; obverse olivaceous grey to iron grey; with aerial mycelium pale mouse grey, sparse, or absent; reverse olivaceous grey.

Material examined: The Netherlands, Utrecht, isolated from meal, unknown date, De Graaff, culture CBS 103.36. Spain, Galicia, isolated from forest soil, unknown date, M. Hernández-Restrepo, CBS 132489 = FMR 11941.

Notes: Traditionally, Monodictys was characterised by brown muriform conidia produced from monoblastic cylindrical conidiogenous cells (Ellis 1971). From a certain perspective, these can be considered a dictyoconidial analogue to the traditional concepts of the ameroconidial Humicola and phragmoconidial Trichocladium. Species with such dictyoconidia and ontogeny, originally classified in Monodictys, are now scattered over different classes, i.e. Dothideomycetes, Sordariomycetes and Leotiomycetes (Tanaka et al., 2015, Hernández-Restrepo et al., 2017). Phylogenetic evidence based on partial LSU sequences (Hernández-Restrepo et al. 2017) assigned Monodictys nigrosperma to the Chaetomiaceae with a close relationship to Trichocladium. The four-locus phylogenetic analysis in this study shows that this species belongs to Trichocladium. Typification of this species is deferred until representative material from the type locality (USA) is collected.

Trichocladium seminis-citrulli (Sergeeva) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824473. Fig. 57.

Open in a separate window

Fig. 57

Trichocladium seminis-citrulli (CBS 143.58, ex-type culture). A. Colonies from left to right on OA, CMA, MEA and PCA after 5 wk incubation. B. Part of the colony. C. Mature ascomata on OA, top view. D. Mature ascomata on OA, side view. E–F. Ascomata mounted in lactic acid. G. Terminal ascomatal hairs. H. Structure of ascomatal wall in surface view. I. Hyphae and chlamydospore-like structures on hyphae. J. Asci. K. Ascospores. Scale bars: E–F = 100 μm; G–K = 10 μm.

Basionym: Chaetomium seminis-citrulli Sergeeva, Not. Syst. Sect. Crypt. Inst. Bot. Acad. Sci. USSR 11: 113. 1956.

Micromorphology: Ascomata usually immersed in thick aerial hyphae, ostiolate, subglobose to broad ovate, mouse grey to dark mouse grey because of the ascomatal hairs, 120–230 μm high, 120–200 μm diam. Ascomatal wall translucent, ochreous to brown, composed of angular or irregular cells. Ascomatal hairs mainly arising around the ostiole, numerous, spirally coiled with flexuous lower part, 2.5–3.5 μm diam near the base. Asci clavate or fusiform, with spore-bearing part 35–48 × 16.5–19 μm and stalks 11–25 μm long, with 8 biseriate ascospores, evanescent. Ascospores rust brown, broad ovoid or broad pyriform, bilaterally flattened, (11.5–)12–13.5(–15) × (9–)10–11(–12) × (7.5–)8–9.5(–10) μm, with an apical and often protuberant germ pore. Chlamydospore-like structures intercalary formed in chains or clusters, subglobose or ellipsoidal, hyaline, cylindrical, doliiform, 5–12.5 μm diam.

Culture characteristics: Colonies on OA 40–46 mm diam after 7 d at 25 °C; edge entire or lobate; aerial mycelium thick, white to primrose or sulphur yellow, irregularly distributing; soluble pigment ochreous to fulvous; reverse ochreous to apricot. Colonies on CMA similar to those on OA, 35–41 mm diam after 7 d at 25 °C; aerial mycelium thicker than those on OA and covering the whole colonies. Colonies on MEA 35–41 mm diam after 7 d at 25 °C; edge lobate to radially striated; aerial mycelium thick, white; reverse orange caused by soluble pigment. Colonies on PCA 34–40 mm diam after 7 d at 25 °C; edge entire; aerial mycelium absent; soluble pigment; reverse uncoloured.

Material examined: Israel, isolated from dung of goat, unknown date, M. Dreyfuss, culture CBS 637.83. Turkmenistan, isolated from dung of fox, unknown date, K.S. Sergejeva, ex-isotype culture CBS 143.58 = IMI 074953 = VKM F-1952.

Notes: The asexual structures of this species were overlooked in the study by von Arx et al. (1986). They are very similar to those found in T. amorphum, confirming their close relationship; however, T. amorphum does not produce sexual spores (Fig. 45).

Trichocladium uniseriatum (Yu Zhang & L. Cai) X. Wei Wang & Houbraken, comb. nov. MycoBank MB824475.

Basionym: Chaetomium uniseriatum Yu Zhang & L. Cai, Fungal Biol. 121: 33. 2017.

Micromorphology: Fide Zhang et al. (2017a). Ascomata ostiolate, dark grey to black, immersed and covered by the aerial mycelium, spherical or nearly so, 170–270 μm diam. Ascomatal wall brown, composed of textura angularis or irregularis. Ascomatal hairs slightly straight below, spirally coiled in the upper part, dark brown, unbranched, nearly smooth 2.5–3.5 μm wide near the base. Asci cylindrical, with 8 uniseriate ascospores, short-stalked, 52–63 × 8–11 μm. Ascospores arranged uniseriately in the ascus, pale brown, ovate or nearly spherical, 8.5–13 × 8–11.5 × 7–9 μm, without distinct germ pore. Chlamydospores present, subhyaline, globose or subglobose, 9–11 μm diam, usually in intercalary chains.

Culture characteristics: Fide Zhang et al. (2017a). Colonies up to 50 mm diam on PDA after 6 d at 25 °C; aerial mycelium abundant, lanose, yellow; soluble pigment orange or absent; reverse yellow or orange brown.

Notes: Comparison of sequences from Zhang et al. (2017a) with our dataset revealed a close relationship between T. uniseriatum and T. heterothallicum. These species cluster closely with T. amorphum. Trichocladium heterothallicum and T. uniseriatum produce cylindrical asci and intercalary chlamydospores in chains or clusters (Zhang et al. 2017a), providing the morphological evidence that both species are related and belong both to the redefined Trichocladium.

Discussion

The majority of taxonomic studies of Chaetomiaceae focus on sexually reproducing species (von Arx et al 1986, von Arx et al 1988, Wang et al., 2016b, Zhang et al., 2017a, Zhang et al., 2017b). In this study, we focused on integrating hyphomycete genera into the taxonomic outline of this important fungal family. The most important contribution is the linkage of these asexual species to their sexual relatives, more detailed study of the asexual states accompanying perithecial states, and the delimitation of Humicola, Staphylotrichum and Trichocladium as genera including both sexual and asexual species. This is a first step to establish monophyletic concepts for Humicola and Trichocladium as defined by their type species. The taxonomic positions of other species traditionally classified in Humicola and Trichocladium but phylogenetically placed outside Chaetomiaceae are in a preliminary state and should be a subject for future research; a few names known not to belong to Chaetomiaceae are noted above. In addition to these hyphomycetes that lack conidiophores or have micronematous conidiophores, we also studied species of Botryotrichum, Staphylococcum and Gilmaniella, which have similar conidia but more differentiated, branched conidiophores.

Asexual spores in Humicola and related genera are produced on vegetative hyphae or on minimally differentiated conidiophores and are usually thick-walled. In the past, several names were used for the description of these thick-walled spores, such as chlamydospores and aleurioconidia (Hambleton et al. 2005), botryotrichum-like conidia (Hawksworth 1975, Decock & Hennebert 1997) and conidia (Wu & Zhang 2012, Hernández-Restrepo et al. 2017). Typical “botryotrichum-like” conidia are thick-walled and have an irregularly encrusted surface (Domsch et al. 2007). In B. piluliferum, these conidia are produced on branched conidiophores terminating or intermixed with sterile setae (Wang et al. 2016b: Fig. 10, Fig. 11). The combination of these structures is not observed in any species of Humicola and related genera. The term “botryotrichum-like” is therefore not useful to describe the thick-walled spores of Humicola and morphologically similar genera in Chaetomiaceae.

Based on the discussion in the “Introduction”, the thick-walled spores produced by all species of the redefined genera Humicola, Trichocladium and Staphylotrichum in this study could be considered conidia. In Humicola, lateral conidia that arise from a hyphal cell (intercalary conidiogenous cell) are common in each of the investigated species (Fig. 58A–E), which are distinguishable from those in the other genera (Fig. 58 F–N). Such lateral conidia can be used as the diagnostic structures for Humicola. Occasionally, Humicola conidia can also be produced terminally on the short branches of hyphae which could be interpreted as minimally-differentiated (i.e. micronematous) conidiophores. These short branches show no difference from vegetative hyphae. We can also find spores that are morphologically almost identical to the lateral ones but are intercalary in hyaline vegetative hyphae (such as those in H. atrobrunnea, Fig. 6B–C), fitting the usual concept of chlamydospores. Similar conidia are found in several genera and species, including Trichocladium, Staphylotrichum and Botryotrichum verrucosum (= Thermomyces verrucosum), where the distinction from the usual concept of chlamydospores is usually clearer. In Trichocladium, conidium production is mainly present in “subclade 1” (Fig. 1, Fig. 2) and this subclade includes the type species T. asperum. Trichocladium conidiophores are usually pigmented, at least at the upper part, and their conidia are more pigmented and have thicker cell walls than the conidia of Humicola. All the Staphylotrichum species investigated in this study can also produce conidia on denticle-like conidiogenous cells that arise directly from hyphae (micronematous) in addition to their more conspicuous conidia on macronematous conidiophores. Both kinds of conidia are almost identical in shape and size (Fig. 35, Fig. 36, Fig. 37, Fig. 38, Fig. 39, Fig. 40, Fig. 41, Fig. 42, Fig. 58). These conidia are usually hyaline or nearly so with relatively thin cell walls, morphologically resembling the conidia of Humicola. Staphylotrichum conidia easily secede from the conidiogenous cells that produce them, while conidia of Humicola often do not.

Ascospore morphology is a diagnostic character of sexual Humicola species. Ascospores of Humicola are limoniform to quadrangular, bilaterally flattened, and have one apical germ pore. They resemble those of Chaetomium sensu stricto and of one subclade in Collariella (Wang et al. 2016b). No species in the latter genus produces conidia as do the species in Humicola. Furthermore, the limoniform ascospores of Collariella species are produced in ascomata with a darkened collar around the ostiolar pore. Perhaps all Humicola species are genetically capable of producing both conidia and ascospores. However, some may easily lose their sexual structures after long preservation, may require specific culture conditions, or may be heterothallic, as observed in other genera of Chaetomiaceae (e.g. Myceliophthora, Thielavia and Trichocladium).

Acremonium-like synanamorphs were reported in a few Chaetomium species, such as C. elatum and C. rectangulare (Wang et al. 2016a). This study confirmed the occurrence of an acremonium-like morph in several Humicola and Trichocladium species (e.g. H. floriformis, H. pulvericola, H. subspiralis, T. griseum). These acremonium-like structures are usually produced together with thick-walled conidia. There is evidence that some Humicola species are able to produce ascospores together with thick-walled conidia and acremonium-like conidia, for example, H. floriformis (= Chaetomium floriforme) (Gené & Guarro 1996). However, we failed to find ascomata in the degenerated cultures of this species. The acremonium-like morphs are phylogenetically scattered in Chaetomiaceae and are not an informative character for delimiting clades. Often sparsely produced in culture and hidden by ascomata or more conspicuous pigmented conidia, they are difficult to observe and are often missed. We found the inclined coverglass culturing method helpful for observing those structures. But the lack of diagnostic characters associated with this simple morph, combined with their sparseness, makes them of limited value as a taxonomic character.

The connection of asexual Staphylotrichum species to the sexual species S. longicolleum (= Chaetomium longicolleum) is clearly supported by our morphological and molecular data. The micronematously produced conidia (Fig. 58F) are formed in all investigated sexual Staphylotrichum species together with ascomata and ascospores (Fig. 35, Fig. 36, Fig. 37, Fig. 38, Fig. 39, Fig. 40, Fig. 41, Fig. 42). On the other hand, the typical macronematous conidiophores were observed together with sexual structures in one strain of S. longicolleum (CBS 100950, Fig. 40C–D). Another noteworthy observation is that the agar medium influences the mode of conidia formation. For example, cultures on PCA produce conidia on typical conidiophores (macronematous), while cultures on OA or CMA often produce numerous micronematous conidia mixed with macronematous ones. The morphological similarity of thick-walled conidia of Humicola and micronematous conidia of Staphylotrichum can easily result in confusion. Recently, Humicola koreana was described without reference to Staphylotrichum (Li et al. 2016). Comparison of LSU and ITS sequences deposited in GenBank indicated that this species belongs to Staphylotrichum instead of Humicola.

Our concept of Trichocladium includes a high degree of morphological diversity. Four well-supported subclades occur in Trichocladium (Fig. 1, Fig. 2). There is no morphological rationale for splitting the subclades into separate genera in the Trichocladium lineage. Subclade 1 includes species (including the type of the genus, T. asperum) that produce thick-walled conidia and these can have a large morphological diversity (Fig. 58J–K). The other three subclades contain species that reproduce sexually. The hyaline asexual structures observed in T. amorphum (Fig. 45) and T. seminis-citrulli (Fig. 55) might be the undeveloped ascomata. Species with cylindrical asci and ovoid ascospores are found in the subclades 2 and 4, and this character links these two subclades. The phylogenetic distance between the different subclades is low, and this also supports our decision to treat these subclades as one genus.

The redefined concept of Botryotrichum (Wang et al. 2016b) results in another example of a group that exhibits highly diverse morphology. Botryotrichum included asexual species such as B. piluliferum, B. atrogriseum; sexual species producing ostiolate ascomata such as B. murorum (= Chaetomium murorum) and sexual species producing non-ostiolate ascomata such as B. spirotrichum (= Emilmuelleria spirotricha). In this study, the asexual species B. verrucosum (= Thermomyces verrucosus) was added to Botryotrichum. This species produces conidiophores and conidia that are distinct from other Botryotrichum species. Six species were originally described in Thermomyces: Th. dupontii, Th. ibadanensis, Th. lanuginosus, Th. piriformis, Th. stellatus and Th. verrucosus (many of these epithets also classified by some authors in Humicola, see Index Fungorum; http://www.indexfungorum.org, Aug. 2015). Later phylogenetic analyses revealed that Thermomyces is polyphyletic. Houbraken & Samson (2011) showed a close relationship between Talaromyces thermophilus (= Th. dupontii) and Th. lanuginosus (Trichocomaceae, Eurotiomycetes), the type species of the genus. Thermomyces ibadanensis shared ITS sequences with Th. lanuginosus and might be a synonym of the latter species. Thermomyces stellatus belongs to the Microascaceae (Microascales) and the taxonomic position of Th. piriformis is unclear (Houbraken et al. 2014).

Correct identification of a strain is an important step in biological research. The name Mycothermus thermophilus was introduced in 2015 (Natvig et al.), and Humicola insolens and Scytalidium thermophilum are commonly used synonyms of that species. This species attracts attention in biotechnology because of its capability to produce thermostable enzymes and its positive effect in Agaricus bisporus cultivation. The older names H. insolens and S. thermophilum are still frequently used in publications (e.g. Carniel et al., 2017, Meleiro et al., 2017, Meleiro et al., 2018), leading to confusion among researchers unaware that they are actually working with the organism (e.g. Meleiro et al., 2017, Meleiro et al., 2018). Furthermore, identification of My. thermophilus isolates as H. insolens or S. thermophilum incorrectly suggest a close relationship with other Humicola or Scytalidium (Leotiomycetes) species, which could lead to incorrect assumptions in comparative studies. Besides using the correct name, identification can also be hampered because of the use of an insufficiently precise identification marker. Although ITS is the main fungal barcode, different Chaetomiaceae species can share the same ITS sequence (e.g. Trichocladium asperum and T. griseum, Hambleton et al. 2005) and this locus is therefore not always suitable for species identification (Schoch et al., 2012, Wang et al., 2016a). Wang et al. (2016a) evaluated six loci (LSU, ITS, tub2, rpb1, rpb2, tef1) for species of the Chaetomium globosum complex, and the tub2 regions provided the best species resolution (Wang et al. 2016b). Identification using partial tub2 sequences (600–700 bp; primer pairs T1 & TUB4Rd) is recommended here as the alternative identification marker for all Chaetomiaceae. Besides having a good species resolution, this gene also has a high PCR success rate, and public sequence databases (GenBank) are well stocked with beta-tubulin reference sequences. For phylogenetic studies, we recommend sequencing and analysing at least a part of the rpb2 and tub2 region. In our experience, the phylogenetic signal in ITS and LSU is low, and these genes are less appropriate for delimiting genera (and species) in Chaetomiaceae. Selecting reliable reference sequences is also very important. For example, Humicola koreana was described using ITS and LSU sequencing and compared only with Humicola species (Li et al. 2016). However, this species belongs to Staphylotrichum based on our phylogenetic analyses (data not shown).

Species of Chaetomiaceae reported to produce the carcinogenic mycotoxin sterigmatocystin include Botryotrichum pilluliferum, Chaetomium cellulolyticum, C. longicolleum, C. malaysiense, C. udagawae, C. virescens and Humicola fuscoatra (Rank et al. 2011). The taxonomy of the Chaetomiaceae changed significantly in recent years (Wang et al., 2016a, Wang et al., 2016b). Using the latest taxonomic concepts, none of the reported sterigmatocystin producers belongs to Chaetomium sensu stricto. Sterigmatocystin producing species in Chaetomiaceae are distributed over four genera and seven species: Botryotrichum piluliferum (= Ch. piluliferum), Collariella virescens (= Ch. cellulolyticum, Ch. virescens), Humicola fuscoatra, H. malaysiensis (= Ch. malaysiense), H. udagawae (= Ch. udagawae), Staphylotrichum longicolleum (= Ch. longicolleum) and S. tortipilum (CBS 103.79, listed by Rank et al. 2011 under Ch. longicolleum). Based on a poorly understood Chaetomiaceae taxonomy, Rank et al. (2011) speculated that the sterigmatocystin biosynthetic pathway in the Chaetomiaceae evolved independently two times. Based on our updated taxonomy and the phylogenetic relationship among the sterigmatocystin producing species (Fig. 1, Fig. 2), it is tempting to suggest that the pathway evolved at least four times independently. Alternatively, all Chaetomiaceae may have part of or the whole sterigmatocystin gene cluster, i.e. the gene cluster is vertically inherited (Rank et al. 2011). The immediate precursor for aflatoxin, O-methylsterigmatocystin, is produced by species of Humicola, Collariella and Staphylotrichum, which indicates the potential of Chaetomiaceae to produce aflatoxin. Future genome sequencing combined with extrolite analysis of a large set of Chaetomiaceae species will give insight into the distribution and origin of the sterigmatocystin pathway and the potential of each of the Chaetomiaceae species to produce aflatoxin.

The delimitation of the five genera in this study contributes to an integrated phylogeny of the family Chaetomiaceae. The eighteen monophyletic genera currently accepted in the Chaetomiaceae are statistically supported in the rpb2 and the four-locus phylogeny (Fig. 1, Fig. 2). Trichocladium is a sister genus of Ovatospora and Chaetomium, while Myceliophthora and Dichotomopilus are closely related to each other. The thermophilic genera Mycothermus and Remersonia are phylogenetically related. Further studies are needed to establish a comprehensive modern classification of the Chaetomaceae and to give better insight into the evolutionary relationships among the species and genera in the family.

Acknowledgements

Footnotes

References