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Melanospora (Sordariomycetes, Ascomycota) and its relatives
expand article infoYasmina Marin-Felix§, Josep Guarro, José F. Cano-Lira, Dania García, Andrew N. Miller|, Alberto M. Stchigel
‡ Universitat Rovira i Virgili, Reus, Spain
§ Westerdijk Fungal Biodiversity Institute, Utrecht, Netherlands
| University of Illinois, Champaign, United States of America
Open Access

Abstract

The order Melanosporales comprises a large group of ascomycetes, most of them mycoparasites, characterized by the production of usually ostiolate, translucent ascomata, unitunicate asci, and unicellular, pigmented ascospores with germ pores or germ slits. The most studied taxa are Melanospora and Sphaerodes, but the boundaries with other morphologically closely related genera are not well resolved. In this study, the taxonomy of Melanospora and related taxa have been re-evaluated based on the analysis of nuclear rDNA, actin and elongation factor genes sequences of fresh isolates and numerous type and reference strains. The genus Melanospora has been restricted to species with ostiolate ascoma whose neck is composed of intermixed hyphae, and with a phialidic asexual morph. Microthecium has been re-established for species of Melanospora and Sphaerodes without a typical ascomatal neck or, if present, being short and composed of angular cells similar to those of the ascomatal wall, and usually producing bulbils. Three new genera have been proposed: Dactylidispora, possessing ascospores with a raised rim surrounding both terminal germ pores; Echinusitheca, with densely setose, dark ascomata; and Pseudomicrothecium, characterized by ascospores with indistinct germ pores. Dichotomous keys to identify the accepted genera of the Melanosporales, and keys to discriminate among the species of Melanospora and Microthecium, as well as a brief description of the accepted species of both genera, are also provided.

Keywords

Ceratostomataceae, Dactylidispora, Echinusitheca, Melanosporales, Microthecium, Pseudomicrothecium, soil, Sphaerodes, 4 new taxa

Introduction

The family Ceratostomataceae (Winter 1887) includes nearly 100 species, often mycoparasitic and characterized by ostiolate and rostrate, or less frequently non-ostiolate, translucent ascomata, unitunicate and evanescent asci, brown or exceptionally hyaline, unicellular ascospores with a germ pore at each end, or less frequently with only one germ pore or a germ slit, and phialidic asexual morphs or bulbils. Currently, that family is included in the Melanosporales (Chaudhary et al. 2006, Zhang et al. 2006, Hibbett et al. 2007, Li et al. 2016, Schultes et al. 2017), although historically it had been placed in Aspergillales (Gaümann 1964), Hypocreales (Alexopoulos 1962, Spatafora and Blackwell 1994a, Rehner and Samuels 1995, Jones and Blackwell 1998, Zhang and Blackwell 2002) and Sphaeriales (Bessey 1950, Dennis 1968). This family comprises 11 sexually reproducing genera, i.e. Arxiomyces, Melanospora, Persiciospora, Pteridiosperma, Pustulipora, Rhytidospora, Scopinella, Setiferotheca, Sphaerodes, Syspastospora and Vittatispora. Melanospora, the largest genus of this family (more than 50 species), was established by Corda (1837) to accommodate Ceratostoma chionea and two new species, Melanospora zamiae and Melanospora leucotricha, with the former chosen later as the type species (Kowalski 1965). Melanospora is characterized by usually ostiolate ascomata with a long neck and a translucent, pale yellow to reddish brown ascomatal wall, and mostly smooth-walled, brown, ellipsoidal to citriform, rarely discoid or fusoid ascospores, with a depressed germ pore at each end, occasionally surrounded by a raised rim (Guarro et al. 2012). Related genera are Microthecium and Sphaerodes. The former was erected by Corda (1842) to distinguish Mi. zobelii from Melanospora spp. by the presence of non-ostiolate, usually immersed ascomata; and Sphaerodes was introduced by Clements (1909) to separate Melanospora episphaeria from Melanospora spp. by its reticulate ascospores. However, the generic boundaries between Melanospora and its relatives remained obscure. Doguet (1955) carried out a revision of Melanospora, synonymizing several species and transferring additional species from other genera, mostly from Sphaeroderma, which had been proposed by Fuckel (1877) and distinguished from Melanospora by the absence of an ascomatal neck. Doguet (1955) considered the production of a neck as a non-stable taxonomic character influenced by the nature of the substrate where the fungus grows, and segregated the genus in several sections on the basis of the morphology of the ascomata (presence or absence of neck, and its size when present) and ascospores (shape and ornamentation). The most comprehensive revision of Melanospora and related genera was carried out by Cannon and Hawksworth (1982), based mainly on the structure of the ascospore wall under SEM, resulting in the transfer of species of Microthecium to Melanospora and to Sphaerodes. However, recent molecular studies demonstrated that these two latter genera are polyphyletic (Zhang and Blackwell 2002, Fan et al. 2012, Li et al. 2016, Schultes et al. 2017). Other genera included in the family are: Arxiomyces, which produces ovoid to ellipsoidal ascospores with a rounded apex and a truncate base with a large sunken germ pore (Cannon and Hawksworth 1982, 1983); Persiciospora, characterized by ascospores with a pitted wall and a faint reticulation (Cannon and Hawksworth 1982); Pteridiosperma, with ascospores ornamented with longitudinal wing-like appendages (Krug and Jeng 1979); Pustulipora, distinguished by its ascospores with a germ pore at each end surrounded by a blistered, rarely cushion-like structure showing an irregular pustulate appearance (Cannon 1982); Rhytidospora, characterized by non-ostiolate ascomata with a cephalothecoid ascomatal wall (Krug and Jeng 1979); Scopinella, producing brown, cuboid-ellipsoidal ascospores with two prominent longitudinal germ slits (Cannon and Hawksworth 1982); Setiferotheca, which produces ascospores similar to those of Arxiomyces and ascomata with a crown of dark brown setae surrounding the ostiole (Matsushima 1995); Syspastospora, possessing ascomata with a long neck composed of parallel arranged hyphae and cylindrical ascospores with a large terminal slightly sunken germ pore at each end (Cannon and Hawksworth 1982); and Vittatispora, which produces ascomata similar to those of Syspastospora and citriform ascospores with a longitudinal, thick, hyaline ridge (Chaudhary et al. 2006). Practically all taxonomic studies on these fungi have been based exclusively on the morphological characterization of the reproductive structures of preserved fungarium specimens, since unfortunately due to their mycoparasitism, many of these fungi do not grow in pure culture or do not produce ascomata in absence of their hosts. On the other hand, obtaining reliable nucleotide sequences from members of the Melanosporales is also difficult because of the usually large amount of DNA of their hosts. Based on the study of several freshly-isolated soil-borne fungi and of reference and type strains obtained from various culture collections, we have re-examined the phylogenetic relationships of the most relevant genera of the Ceratostomataceae. Consequently, the genus Melanospora has been redefined, Microthecium has been re-established, and three new genera have been proposed.

Materials and methods

Fungal isolates

The strains included in this study are listed in Table 1. Fresh isolates were obtained from samples following previously described procedures for the activation of dormant ascospores in soil using acetic acid and phenol solutions (Stchigel et al. 2001, García et al. 2003). Ascomata were transferred to 55 mm diam. Petri dishes containing oatmeal agar (OA; oatmeal flakes, 30 g; agar-agar, 20 g; distilled water, 1 L) using a sterile needle, which were then incubated at 15, 25 and 35 °C.

Morphological study

For cultural characterization, isolates were grown for up to 30 d on OA, potato carrot agar (PCA; grated potatoes, 20 g; grated carrot, 20 g; agar-agar, 20 g; L-chloramphenicol, 100 mg; distilled water, 1 L), and potato dextrose agar (PDA; Pronadisa, Madrid, Spain) at 5, 10, 15, 20, 25, 30, 35 and 40 °C. Color notations in parentheses are from Kornerup and Wanscher (1984). Vegetative and reproductive structures were examined under an Olympus BH-1 brightfield microscope by direct mounting in lactic acid and water of the ascomata and/or microcultures grown on OA and PDA. Pictures were obtained with a Zeiss Axio Imager M1 brightfield microscope. The samples for scanning electron microscopy (SEM) were processed according to Figueras and Guarro (1988), and SEM micrographs were taken at 15 keV with a Jeol JSM 840 microscope.

Molecular study

The DNA of the fungal isolates (Table 1) was extracted and purified directly from the colonies according to the Fast DNA Kit protocol (MP Biomedicals, Solon, Ohio). The amplification of the small subunit (SSU), the D1−D3 domains of the large subunit (LSU) and the internal transcribed spacer region (ITS) of the nuclear rDNA, and the fragments of actin (act) and translation elongation factor 1-α (tef1) genes were performed according to White et al. (1990) (SSU), Vilgalys and Hester (1990) (LSU), Cano et al. (2004) (ITS), Voigt and Wöstermeyer (2000) (act) and Houbraken et al. (2007) (tef1). A BigDye Terminator 3.1 cycle sequencing kit (Applied Biosystems Inc., Foster City, California) was used to sequence both strands with a combination of the same primers used in the amplification. PCR products were purified and sequenced at Macrogen Europe (Amsterdam, The Netherlands) with a 3730XL DNA analyzer (Applied Biosystems), and the consensus sequences were obtained using SeqMan (version 7.0.0; DNASTAR, Madison, WI, USA). A phylogenetic study based on the analysis of SSU sequences of the isolates and type and reference strains of the Melanosporales and of some members of the Chaetosphaeriales, Coniochaetales, Coronophorales, Hypocreales, Microascales, Sordariales and Xylariales, using Thelebolus ellipsoideus (Thelebolales) as outgroup, was performed to confirm the taxonomic placement of our isolates. A subsequent study, carried out to infer the phylogenetic relationships among members of the Melanosporales, was based on the analysis of a combined data set including the ITS, LSU, act and tef1 sequences of our isolates and of type and reference strains of a large number of the Melanosporales, including Nectria cinnabarina and Pseudallescheria fusoidea as outgroups. The Maximum-Likelihood (ML) and Bayesian Inference (BI) methods were used in phylogenetic analyses as described by Hernández-Restrepo et al. (2016). Bootstrap support (BS) ≥70 and posterior probability values (PP) ≥0.95 were considered significant. The sequences generated in this study were deposited in GenBank (Table 1 and Fig. 1) and the alignments used in the phylogenetic analyses were deposited in TreeBASE (http://purl.org/phylo/treebase/phylows/study/TB2:S17079). Sequences retrieved from GenBank and NBRC included in the SSU and combined analyses are shown in Fig. 1 and Table 1, respectively.

Figure 1. 

RAxML phylogram obtained from SSU sequences of isolates and type and reference strains included in the Melanosporales, and strains belonging to the orders Chaetosphaeriales, Coniochaetales, Coronophorales, Hypocreales, Microascales, Sordariales and Xylariales. Thelebolus ellipsoideus was used as outgroup. RAxML bootstrap support (BS) values above 70 % and Bayesian posterior probability scores above 0.95 are shown at the nodes. Type strains of the different species are indicated with T.

Isolates and reference strains of members of Melanosporales included in the combined phylogenetic study.

Taxa Strain Source GenBank accession number
LSU ITS act tef1
Dactylidispora ellipsospora NBRC 31376T Forest soil, Papua New Guinea, Buin, Bougainville Island KP981451 03137601* KP981545 KP981579
Dactylidispora singaporensis NBRC 30865T Soil, Singapore KP981452 03086502* KP981546 KP981580
Echinusitheca citrispora CBS 137837T
= FMR 12767T
Forest soil, USA, North Carolina, Great Smoky Mountains National Park, Cataloochee Creek Campground KP981453 KP981477 KP981547 KP981581
Nectria cinnabarina CBS 127383 Austria, Niederösterreich, Litschau HM534894 HM534894 HM534873
Melanospora damnosa CBS 113681 Soil, France, Pont d’Espagne KP981454 KP981478 KP981543 KP981582
Melanospora kurssanoviana NBRC 8098 Unknown KP981455 KP981479 KP981548 KP981583
Melanospora verrucispora NBRC 31375T Forest soil, Papua New Guinea, Kebil, Chimb Dist. KP981456 KP981480 KP981549 KP981584
Melanospora zamiae NBRC 7902 Unknown KP981457 00790201* KP981544 KP981585
Microthecium ciliatum NBRC 9829 Soil, unknown KP981458 KP981481 KP981524 KP981586
Microthecium compressum NBRC 8627 Unkown KP981459 00862701* KP981525 KP981587
Microthecium fayodii FMR 12363 Soil, Tennessee, Great Smoky Mountains National Park, Cosby Creek trail KP981460 KP981482 KP981526 KP981588
Microthecium fimbriatum NBRC 8523 Unknown KP981461 KP981483 KP981527 KP981589
Microthecium fimicola NBRC 8354 Unknown KP981462 KP981484 KP981528 KP981590
FMR 5483 Soil, Australia, Moara KP981463 KP981485 KP981529 KP981591
FMR 12370 Soil, Spain, Gran Canaria KP981464 KP981486 KP981530 KP981592
FMR 13418 Soil, Spain, Aragon, Los Valles Occidentales KP981465 KP981487 KP981531 KP981593
Microthecium fusisporum NBRC 8806 Unknown KP981466 00880601* KP981532 KP981594
Microthecium japonicum FMR 12371 Soil, Spain, Gran Canaria, Pico de Osorio KP981467 KP981488 KP981533 KP981595
Microthecium levitum FMR 6218
= CBS 966.97
Soil, Nepal, Bhadgaon KP981468 KP981489 KP981534 KP981596
FMR 10098 Soil, Nigeria, Enugu, Nsukka KP981469 KP981490 KP981535 KP981597
FMR 13884 Soil, Spain, Catalonia, Vall Fosca KP981470 KP981491 KP981536 KP981598
Microthecium quadrangulatum CBS 112763T Soil, Spain, Asturias, Muniellos Biological Absolute Reserve KP981471 KP981492 KP981537 KP981599
Microthecium retisporum NBRC 8366 Soil, Japan KP981472 00836601* KP981538 KP981600
Microthecium sepedonioides FMR 11933 Forest soil, Spain, Aragón, valle de Ordesa KP981473 KP981493 KP981539 KP981601
Microthecium sp. FMR 6725
= CBS 102190
Desert soil, Egypt, Sinai KP981474 KP981494 KP981540 KP981602
Microthecium sp. FMR 7183
= CBS 108937
Forest soil, New South Wales, Sydney, Blue Mountains KP981475 KP981495 KP981541 KP981603
Microthecium tenuissimum CBS 112764T Soil, Spain, Murcia, Sierra de Espuña, Umbria de Peña Apartada KY628706 KY628705
Microthecium zobelii NBRC 9442 Decaying carpophore of Coriolus flabelliformis KP981476 00944201* KP981542 KP981604
Pseudallescheria fusoidea CBS 106.53T Soil, Panama, Guipo EF151316 AY878941
Pseudomicrothecium subterraneum BJTC FAN1001T From Tuber indicum, China, Yunnan JN247804
Vittatispora coorgii BICC 7817T Soil, India, Western Ghats, Coorg District, Kakkabe DQ017375

Results

The SSU phylogenetic study was based on an alignment of 1023 bp and produced a single ML tree (Fig. 1) inferred from a RAxML analysis. The members of the Melanosporales including our isolates were placed in a highly supported main clade (100 % BS / 0.99 PP), and the isolate CBS 137837, whose morphological features did not match any previously described taxon, occurred as a basal branch clearly separated from the other Melanosporales, which grouped together with a high support (95 % BS / 0.98 PP) and separated into three subclades. The first one (96 % BS / - PP), contained most of the isolates morphologically identified as Melanospora, Persiciospora and Sphaerodes, including the type and reference strains of Melanospora brevirostris, M. fimbriata, M. fusispora, M. levita, M. zobelii, Papulaspora sepedonioides, Pteridiosperma ciliatum, Sphaerodes compressa, S. fimicola, S. retispora, S. quadrangularis and S. tenuissima, without significant genetic variation among them. The second subclade (80 % BS / - PP) comprised the type strains of Sphaerodes ellipsospora and Sphaerodes singaporensis and a reference strain of Melanospora kurssanoviana, which resulted clearly separated from the other two, which grouped with high support (100 % BS / 0.98 PP). In the third subclade (100 % BS / 1 PP) were nested the type species of Melanospora (M. zamiae), the type strains of Melanospora verrucispora and Sphaerodes mycoparasitica, and reference strains of Melanospora damnosa and Melanospora tiffanii.

The lengths of the individual alignments used in the combined data set were 802 bp (LSU), 535 bp (ITS), 727 bp (act) and 846 bp (tef1), respectively, and the final total alignment was 2910 bp. In the ML tree derived from the RAxML analysis of the combined data set (Fig. 2), the Melanosporales were highly supported (100 % BS / 1 PP) and subdivided into seven lineages. The first clade (89 % BS / 1 PP; Clade Microthecium) grouped all our isolates, with the exception of CBS 137837, and type or reference strains of Melanospora fimbriata, M. fusispora, M. levita, M. zobelii, Papulaspora sepedonioides, Pteridiosperma ciliatum, Sphaerodes compressa, S. fimicola, S. retispora, S. quadrangularis and S. tenuissima. All the fungi belonging to this clade have non-ostiolate ascomata, or when a neck is present, it is short and composed of angular cells similar to those of the ascomatal wall. Also, bulbils (microsclerotial-like asexual propagules) are present in most of these species. In spite of the high morphological variability shown by members of this clade, the loci used in the phylogenetic analysis were not able to separate the species from each other. The second clade (100% BS / 1 PP; Clade Melanospora) comprised the type species of Melanospora, M. zamiae, the type strain of M. verrucispora and a reference strain of M. damnosa. The members of this clade produce ostiolate ascomata with a long neck composed of hyphae irregularly arranged and ending in a crown of setae. In addition, an asexual morph is commonly present, which is characterized by solitary, sessile, flask-shaped phialides producing from rounded to ellipsoidal conidia. The third lineage comprised only a reference strain of Melanospora kurssanoviana, which failed to sporulate in pure culture. The fourth clade (90 % BS / 0.98 PP; Clade Dactylidispora) was composed of the type strains of Sphaerodes ellipsospora and S. singaporensis, both characterized by ascospores with a raised rim surrounding the germ pores. Finally, the isolate CBS 137837 and the type strains of Melanospora subterranea and Vittatispora coorgii formed three independent branches. The isolate CBS 137837 produces globose, non-ostiolate, densely setose, dark ascomata and smooth-walled ascospores with a depressed germ pore at each end, while the other two species of this clade also possess morphological features unique in the Melanosporales, e.g. ascospores with indistinct germ pores in M. subterranea and with a longitudinal, thick, hyaline ridge in V. coorgii.

Figure 2. 

RAxML phylogram obtained from the combined ITS, LSU, act and tef1 sequences of our isolates and type and reference strains of the order Melanosporales. Nectria cinnabarina and Pseudallescheria fusoidea were used as outgroup. RAxML bootstrap support (BS) values above 70 % and Bayesian posterior probability scores above 0.95 are shown at the nodes. GenBank accession numbers are indicated in Table 1. Type strains of the different species are indicated with T.

Taxonomy

Key to the accepted genera of the Melanosporales producing sexual morphs (adapted from Cannon and Hawksworth 1982)

1 Ascospores with two longitudinal germ slits Scopinella
Ascospores with germ pores 2
2 Ascospores with a broad germ pore and a small basal appendage 3
Ascospores with a germ pore at each end 4
3 Ascomata with a crown of dark brown setae surrounding the ostiole Setiferotheca
Ascomata without setae Arxiomyces
4 Ascospores oblong or cylindric-fusiform, and germ pores crateriform Syspastospora
Ascospores and germ pores otherwise 5
5 Ascomata ostiolate; neck long, composed of hyphae 6
Ascomata non-ostiolate or ostiolate; neck absent or short, conical, composed of angular cells similar to those of the ascomatal wall 7
6 Neck composed of irregularly arranged hyphae Melanospora
Neck composed of parallel arranged hyphae Vittatispora
7 Ascospores with indistinct germ pores Pseudomicrothecium
Ascospores with conspicuous germ pores 8
8 Germ pores surrounded by hyaline structures 9
Germ pores without such structures 10
9 Germ pores with a raised rim Dactylidispora
Germ pores with a blistered, rarely cushion-like structure Pustulipora
10 Ascomatal wall cephalothecoid Rhytidospora
Ascomatal wall not cephalothecoid 11
11 Ascomata dark, densely setose Echinusitheca
Ascomata translucent, glabrous or surrounded by hyphae-like hairs Microthecium

Dactylidispora Y. Marín, Stchigel, Guarro & Cano, gen. nov.

MycoBank No: 812079

Type species

Dactylidispora ellipsospora (Takada) Y. Marín, Stchigel, Guarro & Cano. Holotype and ex-type strain: NBRC 31376.

Description

Ascomata superficial, globose to pyriform, ostiolate or not, yellowish-brown, appearing dark brown when the ascospores are mature, glabrous or setose; necks cellular, short, conical, with a crown of setae surrounding the ostiole; ascomatal wall membranaceous, of textura angularis. Paraphyses absent. Asci 8-spored, broadly clavate, short-stipitate, without apical structures, evanescent. Ascospores one-celled, at first hyaline, becoming brown to dark brown when mature, fusiform or citriform, umbonate and truncate at the ends, smooth-walled, with one germ pore at each end; germ pores depressed, surrounded by a raised rim. Conidiophores reduced to conidiogenous cells. Conidiogenous cells phialidic, solitary, flask-shaped. Conidia hyaline, subglobose to ovoid, smooth-walled.

Etymology

From Greek δακτυλίδης–, ring, and from Latin –spora, spore, due to the raised rim that surrounds the germ pores of the ascospores.

Notes

The most distinctive characteristic of Dactylidispora is the production of smooth-walled ascospores with a germ pore at each end surrounded by a raised rim. Vittatispora, proposed as a new genus by Chaudhary et al. (2006), also produces a raised rim surrounding the germ pores. However, both genera can be easily distinguished by the nature of the ascomatal neck, which is composed of angular cells in Dactylidispora and of parallel arranged hyphae in Vittatispora; and by the presence of a hyaline ridge running the entire vertical length of the ascospore between the germ pores in Vittatispora. Moreover, in our phylogenetic study (Fig. 2), Vittatispora also constituted a lineage independent from the other members of the Melanosporales. Pustulipora is also morphologically similar to Dactylidispora being characterized by blistered, rarely cushion-like structures surrounding the germ pore (Cannon 1982). However, unfortunately, Pustulipora could not be included into this phylogenetic study since living cultures were not available.

The presence of a raised rim was also described in Melanospora collipora (Stchigel et al. 1997), which is here transfered to Dactylidispora even though it was not possible to include this species in the phylogenetic study.

Dactylidispora collipora (Stchigel & Guarro) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812080

Melanospora collipora Stchigel & Guarro, in Stchigel, Guarro & Figueras, Mycol. Res. 101: 446. 1997. [Basionym]

Notes

This species produces ascomata with a crown of setae around the ostiole, ellipsoidal ascospores, and bulbils.

Dactylidispora ellipsospora (Takada) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812081

Microthecium ellipsosporum Takada, in Kobayasi et al., Bull. natn. Sci. Mus., Tokyo 16: 527. 1973. [Basionym]

Sphaerodes ellipsospora (Takada) D. García, Stchigel & Guarro, Stud. Mycol. 50: 67. 2004.

Notes

Dactylidispora ellipsospora is characterized by non-ostiolate ascomata, fusiform ascospores and absence of asexual morph.

Dactylidispora singaporensis (Morinaga, Minoura & Udagawa) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812082

Melanospora singaporensis Morinaga, Minoura & Udagawa, Trans. Mycol. Soc. Japan 19: 142. 1978. [Basionym]

Sphaerodes singaporensis (Morinaga, Minoura & Udagawa) D. García, Stchigel & Guarro, Stud. Mycol. 50: 67. 2004.

Notes

Dactylidispora singaporensis is distinguished by its ostiolate ascomata, citriform ascospores, and phialidic asexual morph.

Echinusitheca Y. Marín, Stchigel, Dania García, Guarro, A.N. Mill. & Cano, gen. nov.

MycoBank No: 812084
Fig. 3

Type species

Echinusitheca citrispora Y. Marín, Stchigel, Dania García, Guarro, A.N. Mill. & Cano. Holotype and ex-type strain, respectively: CBS H-21596, CBS 137837 = FMR 12767.

Description

Ascomata superficial or immersed, solitary to gregarious, globose, non-ostiolate, strongly setose, semi-translucent, pale brown to brown, appearing black when ascospores are mature; setae straight, becoming sinuous toward apex, pale brown to brown, non-septate, rarely 1-septate, thick-walled, verrucose to tuberculate, sometimes branched; ascomatal wall membranaceous, of textura angularis to textura globulosa. Asci 8-spored, globose to subglobose, non-stipitate, without apical structures. Ascospores at first hyaline, becoming brown to dark brown when mature, ellipsoidal, one-celled, smooth-walled, with a depressed germ pore at each end.

Figure 3. 

Echinusitheca citrispora (CBS 137837T). A Ascomata B Asci C, D Ascospores E Depressed germ pore. Scale bars: 50 μm (A); 10 μm (B); 5 μm (C, D); 1 μm (E).

Etymology

From Latin echinus–, sea urchin, and from Greek –τείχος, wall, because of the ascomata resemblance to a sea urchin, due to the abundance of setae.

Notes

This genus is characterized by dark, strongly setose, non-ostiolate ascomata. Apart from Echinusitheca, the other genera of the Melanosporales characterized by the production of dark semi-translucent ascomata are Arxiomyces and Scopinella, but both genera differ from Echinusitheca by the production of long ascomatal necks. Moreover, Scopinella can be easily distinguished from Echinusitheca by its cuboid-ellipsoidal ascospores with two prominent longitudinal germ slits, and Arxiomyces by its ellipsoidal ascospores that are rounded at the apex and truncated at the base, and with a broad germ pore that bears a mucilaginous and collapsing appendage.

Echinusitheca citrispora Y. Marín, Stchigel, Dania García, Guarro, A.N. Mill. & Cano, sp. nov.

MycoBank No: 812085
Fig. 3

Type

USA, North Carolina, Great Smoky Mountains National Park, Cataloochee Creek Campground (35.1375; -83.4915), forest soil, 15 July 2008, A.N. Miller, M. Calduch and A.M. Stchigel, holotype CBS H-21596, cultures ex-type CBS 137837 = FMR 12767.

Description

Colonies on PDA attaining a diam. of 70–75 mm after 14 d at 35 °C, cottony and granulose due to the presence of a large number of ascomata, white with grey to black dots, depressed at the centre and margins fringed; reverse yellowish-white to pale yellow (4A2 to 4A3) and with olive brown (4F2) dots. Colonies on OA attaining a diam. of 50–60 mm in 14 d at 35 °C, cottony and granulose due to the presence of numerous ascomata, margins arachnoid, white to orange white (5A2) with brownish grey dots (5F2); reverse yellowish-white to golden grey (4A2 to 4C2). Minimum, maximum, and optimum temperature of growth are 20, 40 and 35 °C, respectively. Mycelium composed of hyaline to pale yellow, septate, branched, smooth-walled hyphae, 1–3 µm diam. Ascomata non-ostiolate, immersed into the mycelium, solitary or gregarious, globose, 130–280 µm diam., setose, semi-translucent, pale brown to brown, appearing black when ascospores are mature; setae straight, becoming sinuous toward apex, 20–200 µm long, 5–20 µm wide at base, tapering gradually to a rounded tip of 2–5 µm diam., pale brown to brown, non-septate or rarely 1-septate, thick-walled, verrucose to tuberculate, sometimes branched at apex; ascomatal wall membranaceous, 30–40 µm thick, composed of 5–6 layers of flattened cells of 5–30 µm diam. of textura angularis to textura globulosa. Asci 8-spored, globose to subglobose, 20–25 × 15–20 µm, soon evanescent, non-stipitate, without apical structures, irregularly disposed at the centrum. Ascospores irregularly arranged in the asci, one-celled, at first hyaline, becoming brown to dark brown when mature, smooth- and thick-walled, ellipsoidal, 20–27 × 10–15 µm, with one germ pore at each end; germ pores 0.75–2 µm diam., depressed. Asexual morph absent.

Etymology

From Latin citrum-, lemon, and -spora, spore, referring to the lemon-shaped ascospores.

Melanospora Corda, Icon. fung. (Prague) 1: 24. 1837, emend.

Fig. 4

Type species

Melanospora zamiae Corda, Icon. fung. (Prague) 1: 24. 1837. Representative strain: NBRC 7902.

Description

Ascomata superficial to immersed, globose to subglobose, ostiolate, yellowish-orange or reddish, tomentose or glabrous, usually with a long neck composed of intermixed hypha, with a crown of rigid, hyaline, septate, smooth- and thick-walled setae; ascomatal wall membranaceous, translucent, of textura angularis. Periphyses present. Paraphyses absent. Asci 8-spored, clavate, rounded at apex, without apical structures, thin-walled, evanescent. Ascospores one-celled, at first hyaline, becoming brown to dark brown when mature, fusiform, ellipsoidal or citriform, smooth-walled, reticulate or verrucose, with a terminal apiculate or depressed germ pore at each end. Asexual morph phialidic, hyaline. Bulbils uncommon.

Notes

This genus is distinguished by translucent ascomata with a neck composed of intermixed hyphae and with an apical crown of setae, smooth or ornamented ascospores with an apiculate germ pore at each end, and a phialidic asexual morph. The neck of Melanospora spp. is morphologically similar to those of Syspastospora and Vittatispora, which are also composed of hyphae. Syspastospora was introduced in 1982 by Cannon and Hawksworth to accommodate Melanospora parasitica, with three additional species described later (S. boninensis, S. cladoniae and S. tropicalis). This genus differs from Melanospora in the production of cylindrical to barrel-shaped ascospores with a large, slightly sunken germ pore at both ends (ellipsoidal, citriform or fusiform, having much smaller, apiculate or depressed germ pores in Melanospora). Vittatispora can be distinguished from Melanospora by the production of ascospores with a thick, hyaline, longitudinal ridge and a raised rim surrounding the germ pores. Moreover, Syspastospora and Vittatispora differs from Melanospora in the structure of the ascomatal neck, which is composed of hyphae in a parallel arrangement in both genera (interwoven hyphae in Melanospora).

Melanospora is now restricted to species with ascoma bearing a neck composed of interwoven hyphae and mostly ending in a crown of setae. This kind of neck differentiates this genus from Microthecium, which has a neck composed of angular cells similar to those of the ascomatal wall and possessing a crown of setae surrounding the ostiole rather than disposed at apex of the neck. The only exception is Melanospora mycoparasitica that does not have this sort of neck, being short, cellular and without the crown of setae at the top of this, although this could be due to the fact that it was described and illustrated at an early stage of ascomal development. In a study on the development and cytology of Melanospora tiffanii, Kowalski (1965) illustrated early stages of development with the neck appearing similar to that of M. mycoparasitica.

Long hyphal necks are produced in Melanospora arenaria, Melanospora caprina, Melanospora chionea, Melanospora langenaria, Melanospora longisetosa and Melanospora washingtonensis; therefore, these have been kept in the emended genus Melanospora, although they were not included in the phylogenetic study.

Figure 4. 

Morphological features of the genus Melanospora. Melanospora damnosa (CBS 113681). A Ascoma B Ascomatal neck D Detail of hyphal neck F Ascospores H Ascospore germinating. Melanospora zamiae (NBRC 7902) C Ascomatal neck E Detail of ascomatal wall. Melanospora verrucispora (NBRC 31375T) G Ascospores I Phialidic asexual morph. Scale bars: 50 μm (A); 10 μm (B–E, I); 5 μm (F–H).

Key to the species of Melanospora

1 Ascospores with the surface ornamented 2
Ascospores smooth-walled 4
2 Ascospores irregularly verrucose M. verrucispora
Ascospores reticulate 3
3 Ascospores coarsely reticulate M. mycoparasitica
Ascospores slightly reticulate M. tiffanii
4 Ascospores discoid-ellipsoidal 5
Ascospores otherwise 7
5 Asci 4-spored; ascospores 14–19 × 12–14 × 8–9 μm M. longisetosa
Asci 8-spored; ascospores smaller 6
6 Neck 250–400 μm long; ascospores 7.5–16 × 6–12 × 4–7 μm M. chionea
Neck 150–200(–260) μm long; ascospores 10.5–12(–13.5) × 9–10.5(–12) × 7–9 μm M. washingtonensis
7 Ascomata usually narrower than 100 μm; ascospores citriform to rhomboidal M. damnosa
Ascomata usually broader than 100 μm; ascospores ellipsoidal to citriform 8
8 Ascomata strongly tomentose; neck 1500–2000 μm long M. caprina
Ascomata weakly or not tomentose; neck shorter than 1500 μm 9
9 Neck shorter than 250 μm long M. zamiae
Neck longer than 800 μm long 10
10 Setae longer than 100 μm M. arenaria
Setae up to 50 μm long M. lagenaria

Melanospora arenaria L. Fisch. & Mont., in Montagne, Annls. Sci. Nat., Bot., sér. 4 5: 337. 1856.

Notes

Melanospora arenaria is characterized by ascomata with a long neck and ellipsoidal to citriform, smooth-walled ascospores. It is similar to Melanospora caprina, but differs in having less tomentose ascomata with a shorter neck. Also, it is similar to M. lagenaria, differing only by the size of the setae at the top of the ascomatal neck. Molecular data is necessary to confirm that both species correspond to different species since the size of the setae could be influenced by the culture media on where these grew.

Melanospora caprina (Fr.) Sacc., Syll. fung. (Abellini) 2: 462. 1883.

Sphaeria caprina Fr., Fl. Danic. 11: tab. 1859, fig. 2. 1825. [Basionym]

Ceratostoma caprinum (Fr.) Fr., Summa veg. Scand., Section Post. (Stockholm): 396. 1849.

Cerastoma caprinum (Fr.) Quél., Mém. Soc. Émul. Montbéliard, Sér. 2 5: 522. 1875.

= Sphaeria vervecina Desm., Annls Sci. Nat., Bot., sér. 2 17: 13. 1842.

Melanospora vervecina (Desm.) Fuckel, Jb. nassau. Ver. Naturk. 23-24: 126. 1870.

= Melanospora vervecina f. arundinis Sacc., Syll. fung. (Abellini) 2: 461. 1883.

Notes

Melanospora caprina is distinguished from the other species of the genus by its larger, white, densely tomentose ascomata with a very long neck, and ellipsoidal to citriform, smooth-walled ascospores with slightly apiculate germ pores.

Melanospora chionea (Fr.) Corda, Icon. fung. (Prague) 1: 24. 1837.

Ceratostoma chioneum Fr., Observ. mycol. (Havniae) 2: 340. 1818. [Basionym]

Sphaeria chionea (Fr.) Fr., Syst. mycol. (Lundae) 2: 446. 1823.

Melanospora chionea var. chionea (Fr.) Corda, Icon. fung. (Prague) 1: 24, tab. 7, fig. 297. 1837.

= Sphaeria biformis var. brachystoma Pers., Syn. meth. fung. (Göttingen) 1: 60. 1801.

Melanospora chionea var. brachystoma (Pers.) Sacc., Syll. fung. (Abellini) 2: 461. 1883.

= Sphaeria leucophaea Fr., Elench. fung. (Greifswald) 2: 92. 1828.

Ceratostoma leucophaeum (Fr.) Fr., Summa veg. Scand., Section Post. (Stockholm): 396. 1849.

Melanospora chionea var. leucophea (Fr.) Sacc., Syll. fung. (Abellini) 2: 461. 1883.

= Melanospora antarctica Speg., Boln Acad. nac. Cienc. Córdoba 11: 233. 1888.

Notes

This species is characterized by white, tomentose ascomata and discoid, smooth-walled ascospores with depressed germ pores.

Melanospora damnosa (Sacc.) Lindau, in Engler & Prantl, Nat. Pflanzenfam., Teil. I (Leipzig) 1: 353. 1897.

Fig. 4A, B, D, F, H

Sphaeroderma damnosum Sacc., Riv. Patol. veg. 4: 64. 1895. [Basionym]

Notes

Melanospora damnosa is distinguised by the production of ascomata with a short neck and citriform to rhomboidal, smooth-walled ascospores with a slightly apiculate germ pore at each end.

Melanospora lagenaria (Pers.) Fuckel, Jb. nassau. Ver. Naturk. 23-24: 126. 1870.

Sphaeria lagenaria Pers., Syn. meth. fung. (Göttingen) 1: 58. 1801. [Basionym]

Ceratostoma lagenaria (Pers.) Fr. [as ‘lagenarium’], Syst. veg., Edn 16: 392. 1827.

Auerswaldia lagenaria (Pers.) Rabenh., Hedwigia 1: 116. 1857.

Cerastoma lagenaria (Pers.) Quél., Mém. Soc. Émul. Montbéliard, Sér. 2 5: 522. 1875.

Phaeostoma lagenaria (Pers.) Munk [as ‘lagenarium’], Dansk bot. Ark. 17: 82. 1957.

= Melanospora lagenaria var. tetraspora Rehm, Hedwigia 30: 259. 1891.

Notes

Melanospora lagenaria is similar to M. caprina, but the former has less tomentose ascomata with shorter necks ending in a poorly developed crown of setae. This species is also similar to M. arenaria. For morphological comparison see Notes of the latter species.

Melanospora longisetosa P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 130. 1982.

Notes

This species is characterized by the formation of 4-spored asci and discoid, smooth-walled ascospores.

Melanospora mycoparasitica (Vujan.) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812086

Sphaerodes mycoparasitica Vujan., Mycol. Res. 113: 1173. 2009. [Basionym]

Notes

Melanospora mycoparasitica is distinguished by its fusiform, coarsely reticulate ascospores.

Melanospora tiffanii Kowalski, Mycologia 57: 279. 1965.

Notes

This species is distinguished by its fusiform, slightly reticulate ascospores.

Melanospora verrucispora Takada, in Kobayasi et al., Bull. natn. Sci. Mus., Tokyo 16: 525. 1973.

Fig. 4G, I

Notes

This species is characterized by irregularly verrucose ascospores.

Melanospora washingtonensis Nitzan, J.D. Rogers & D.A. Johnson, Sydowia 56: 282. 2004.

Notes

This species is similar to M. chionea, but they differ in the length of the neck [150–200(–266) μm in M. washingtonensis vs. 250–400 μm in M. chionea] and in the size of the ascospores [10.5–12(–13.5) × 9–10.5(–12) × 7–9 μm in M. washingtonensis vs. 7.5–16 × 6–12 × 4–7 μm in M. chionea], as well as in the presence of a phialidic asexual morph in M. washingtonensis.

Melanospora zamiae Corda., Icon. fung. (Prague) 1: 24. 1837.

Fig. 4C, E

= Melanospora leucotricha Corda, Icon. fung. (Prague) 1: 25. 1837.

= Melanospora coemansii Westend., Bull. Acad. R. Sci. Belg., Cl. Sci., sér. 2 2: 579. 1857.

= Melanospora cirrhata Berk. in Cooke, Grevillea 16: 102. 1888.

= Melanospora globosa Berl., Malpighia 5: 409. 1891.

= Melanospora pampeana Speg., Anal. Mus. nac. Hist. nat. B. Aires 6: 287. 1898.

= Melanospora townei Griffiths, Bull. Torrey bot. Club 26: 434. 1899.

= Melanospora rhizophila Peglion & Sacc., Annls mycol. 11: 16. 1913.

= Melanospora mattiroloana Mirande [as ‘mattiroliana’], Bull. Soc. mycol. Fr. 32: 72. 1916.

= Melanospora schmidtii Sacc., Syll. fung. (Abellini) 24: 650. 1926.

= Melanospora asclepiadis Zerova, J. Inst. Bot. Acad. Sci. Ukraine 12: 155. 1937.

Notes

Melanospora zamiae is characterized by the production of ellipsoidal to citriform, smooth-walled ascospores with a depressed germ pore at each end. Doguet (1955) described the presence of bulbils; however, later studies did not mention the presence of such sort of propagules (Calviello 1973, Cannon and Hawksworth 1982), which rarely occur in the genus.

Doubtful species

Melanospora aculeata E.C. Hansen, Vidensk. Meddel. Dansk Naturhist. Foren. Kjøbenhavn 59: 15. 1877.

Notes

Cultures of this species are not available, but it was originally described as producing small asci (18–21 × 7–8 μm) and ascospores (4–6 × 3–4 μm). This species produced ostiolate ascomata without a neck, typical of Microthecium; however, such small ascospores have never been seen in Microthecium.

Melanospora endobiotica Woron., Notul. syst. Inst. cryptog. Horti bot. petropol. 3: 31. 1924.

Notes

Cultures are not available, and no illustrations were included in the protologue. It was reported as morphologically similar to Melanospora rhizophila [now considered a synonym of Melanospora zamiae (Doguet 1955)] when it was first described (Woronichin 1924).

Excluded species

Melanospora arachnophila Fuckel, Jb. nassau. Ver. Naturk. 23–24: 127. 1870.

Notes

This species possesses cylindrical asci and hyaline ascospores, features never seen in Melanospora. It was previously excluded from Melanospora by Doguet (1955).

Melanospora argadis Czerepan., Nov. sist. Niz. Rast. 3: 177. 1966.

Notes

This species shows morphological features never observed in Melanospora, e.g. small asci (10–14 × 5–6.5 μm) and olivaceous ascospores (5–5.5 × 3–3.5 μm). The original description is not detailed enough to ascertain its possible taxonomical placement.

Melanospora exsola Bat. & H.P. Upadhyay, Atas Inst. Micol. Univ. Recife 2: 331. 1965.

Notes

This species is excluded from Melanospora due to its dark brown, non-translucent, setose ascomata and its small ascospores (4.5–12 × 4–7 μm), which seem to indicate a closer relationship with Chaetomium.

Melanospora gigantea (Massee & Crossl.) Massee & Crossl., Fungus Flora of Yorkshire (Leeds): 215. 1905.

Notes

Descriptions of this species and of its basionym, Sphaeroderma gigantea, were not found.

Melanospora lucifuga (Jungh.) Sacc., Syll. fung. (Abellini) 2: 464. 1883.

Notes

Cultures are not available, and the original description does not mention asci and ascospores. Therefore, we agree with Doguet (1955) in the exclusion of this fungus from Melanospora.

Melanospora kurssanoviana (Beliakova) Czerepan., Notul. syst. Sect. cryptog. Inst. bot. Acad. Sci. U.S.S.R. 15: 84. 1962.

Notes

In our phylogenetic study, M. kurssanoviana was placed in an independent lineage far from Melanospora. Unfortunately, the only living culture available is sterile. We did not find any distinctive morphological feature to differentiate this species from other members of the Melanosporales in the original description and in the drawing to introduce it as a new genus.

Melanospora macrospora P. Karst., Hedwigia 30: 299. 1891.

Notes

Doguet (1955) excluded this species due to the production of very large cylindrical asci (480–500 × 33–36 μm) and ascospores (42–52 × 28–35 μm), morphological features not observed in any other member of the Melanosporales.

Melanospora octahedrica Pat., Cat. Rais. Pl. Cellul. Tunisie (Paris): 109. 1897.

Notes

This species is transferred to Scopinella due to the morphology of its ascospores, i.e. octahedral ascospores with two prominent longitudinal germ slits.

Scopinella octahedrica (Pat.) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812087

Basionym

Melanospora octahedrica Pat., Cat. Rais. Pl. Cellul. Tunisie (Paris): 109. 1897.

Melanospora pascuensis Stchigel & Guarro, Mycol. Res. 103: 1305. 1999.

Notes

This species is excluded from Melanospora since its neck is cellular or absent, instead it is characterized by a dark ring-like structure around the germ pores of the ascospores (Stchigel et al. 1999). This fungus could represent a new genus since such structure is unique in the Melanosporales, and these kind of structures resulted in being phylogenetically informative, as in the case of Dactylidispora, which is distinguished by its ascospores with a raised rim around the germ pores. The type strain of this specimen was contaminated with another fungus and it could not be included in the molecular study.

Melanospora setchellii (Harkn.) Sacc. & P. Syd., Syll. fung. (Abellini) 16: 564. 1902.

Notes

This species is excluded from Melanospora since it produces cylindrical asci with the ascospores uniseriately disposed, a feature never observed in this genus.

Melanospora vitrea (Corda) Sacc., Syll. fung. (Abellini) 2: 463. 1883.

Sphaeronaema vitreum Corda, Icon. fung. (Prague) 1: 25. 1837. [Basionym]

Notes

Doguet (1955) excluded this species due to its oblong, pale yellow ascospores.

Microthecium Corda, Icon. fung. (Prague) 5: 30, 74. 1842, emend.

Fig. 5

= Sphaerodes Clem., Gen. fung. (Minneapolis): 44, 173. 1909.

= Pteridiosperma J.C. Krug & Jeng, Mycotaxon 10: 44. 1979.

= Persiciospora P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 133. 1982.

Type species

Microthecium zobelii Corda, Icon. fung. (Prague) 5: 74. 1842. Representative strain: NBRC 9442.

Description

Ascomata ostiolate or not, superficial or immersed, globose to subglobose or pyriform, yellowish-orange, orange-brown or reddish, tomentose or glabrous; necks short or absent, conical, composed of angular cells similar to those of the ascomatal wall, usually with a crown of hyaline, septate, smooth- and thick-walled setae around the ostiole; ascomatal wall membranaceous, translucent, of textura angularis. Periphyses present. Paraphyses absent. Asci 8-spored, clavate, rounded at apex, without apical structures, thin-walled, evanescent. Ascospores one-celled, at first hyaline, becoming brown to dark brown when mature, ellipsoidal, fusiform, navicular, citriform, plataniform or spindle-shaped, smooth, reticulate, pitted or wrinkled, with a terminal apiculate or depressed germ pore at each end. Asexual morph phialidic, hyaline. Bulbils usually produced, pale orange to reddish-orange.

Figure 5. 

Morphological features of the genus Microthecium. Microthecium levitum (FMR 10098). A Non-ostiolate ascoma E Asci G Ascospores K Ascospore (SEM). Microthecium fayodii (FMR 12363). B Ostiolate ascomata F Ascospores O Variable shaped bulbils. Microthecium fimicola (FMR 5483). C Detail of cellular neck M Ascospores (SEM) P Bulbil. Microthecium quadrangulatum (CBS 112763T). D Crown of setae around the ostiole L Ascospore SEM. Microthecium retisporum (NBRC 8366). H Ascospores N Asexual morph. Microthecium japonicum (FMR 12371) I Ascospores J Ascospore SEM. Microthecium sepedonioides (FMR 11933) Q Bulbil. Scale bars: 50 μm (A, B, O); 20 μm (C, D); 10 μm (E–I, P, Q); 5 μm (J, L–N); 2.5 μm (K).

Notes

Microthecium has translucent ascomata of textura angularis, cellular necks short or absent, ascospores smooth-walled or ornamented with a depressed or apiculate germ pore at each end, often producing bulbils and a phialidic asexual morph. Dactylidispora, Pustulipora and Pseudomicrothecium produce ascomata similar to Microthecium. However, the two first genera can be distinguished by the presence of a raised rim and blistered structure surrounding the germ pores of the ascospores, respectively, while Pseudomicrothecium differs in the production of 2-spored asci and ascospores with indistinct germ pores.

The species Mi. africanum, Mi. beatonii, Mi. brevirostratum, Mi. episphaerium, Mi. foveolatum, Mi. geoporae, Mi. hypomyces, Mi. internum, Mi. lenticulare, Mi. marchicum, Mi. masonii, Mi. micropertusum, Mi. moureai, Mi. nectrioides, Mi. pegleri and Mi. perplexum were not included in the phylogenetic study because we could not locate any specimens since the holotypes or living cultures of most of them are not available. However, these species were transferred to Microthecium based on their complete and well-illustrated descriptions.

Key to the species of Microthecium

1 Sexual morph absent, only producing bulbils Mi. sepedonioides
Sexual morph present 2
2 Ascomata non-ostiolate 3
Ascomata ostiolate 13
3 Ascospores with an ornamented surface 4
Ascospores smooth-walled or nearly so 8
4 Ascospores pitted and with wing-like ridges Mi. foveolatum
Ascospores coarsely reticulate 5
5 Asci 4-spored 6
Asci 8-spored 7
6 Ascospores (25–)28–34(–40) × 14–18(–20) µm Mi. beatonii
Ascospores 22–28 × 12–15 × 9–11 µm Mi. perplexum
7 Ascospores 25–34 × 12–18 µm Mi. episphaerium
Ascospores 17–20 × 10–12 × 7–9 µm Mi. retisporum
8 Ascomata smaller than 120 µm Mi. tenuissimum
Ascomata longer than 120 µm 9
9 Ascospores shorter than 20 µm 10
Ascospores longer than 20 µm 11
10 Ascospores 15–19 × 11–13 × 8–9 µm, with the narrow faces coarsely reticulate and the others smooth Mi. compressum
Ascospores 10–17 × 8–12 × 9–10 µm, entirely smooth-walled Mi. levitum
11 Ascospores fusiform Mi. hypomyces
Ascospores citriform 12
12 Ascospores 28–30 × 12–13(–15) µm Mi. geoporae
Ascospores 18–25 × 8.5–12 × 6–9 µm Mi. zobelii
13 Ascospores with wing-like appendages 14
Ascospores otherwise 15
14 Ascospores wrinkled, (12–)13–18 × (7–)8–10 µm Mi. ciliatum
Ascospores pitted, (17–)20–22(–24) × 12–14 × 10–12 µm Mi. lenticulare
15 Ascospores ornamentated 16
Ascospores smooth-walled 23
16 Ascospores punctate or punctate-reticulate 17
Ascospores reticulate or striate-reticulate 19
17 Ascospores punctate, ellipsoidal Mi. africanum
Ascospores punctate-reticulate, ellipsoidal-fusiform 18
18 Ascospores delicately punctate, asexual morph and bulbils present Mi. japonicum
Ascospores coarsely punctate, asexual morph and bulbils absent Mi. moreaui
19 Ascospores striate-reticulate 20
Ascospores reticulate 21
20 Ascospores with inconspicuous ridges forming a very coarse reticulum, 18–22(–28) × 9.5–11(–13) × 8–9 µm Mi. micropertusum
Ascospores without ridges or reticulum, 26–36 × 13–17 μm Mi. masonii
21 Ascospores with 4–6 prominent longitudinal ribs Mi. quadrangulatum
Ascospores without longitudinal ribs 22
22 Ascospores spindle-shaped, 19.5–22 × 8.5–11 µm Mi. internum
Ascospores citriform to fusiform, 14–20 × 10–17 µm Mi. fimicola
23 Crown of setae absent Mi. nectrioides
Crown of setae present around the ostiole 24
24 Ascospores citriform Mi. marchicum
Ascospores otherwise 25
25 Ascospores ellipsoid to citriform, often somewhat plataniform 26
Ascospores otherwise 28
26 Bulbils present Mi. fallax
Bulbils absent 27
27 Ascospores 21–34 × 11–17 µm Mi. brevirostrum
Ascospores 18–22 × 9–11 µm Mi. fimbriatum
28 Ascospores ellipsoid to fusiform Mi. fusisporum
Ascospores ellipsoid to navicular 29
29 Ascospores (9.5–)11–12(–13) × 4–4.5 µm Mi. pegleri
Ascospores longer than 15 µm 30
30 Ascospores 16–24 × 8–12 µm Mi. fayodii
Ascospores 25–30 × 11–15 µm Mi. brevirostratum

Microthecium africanum (J.C. Krug) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812088

Persiciospora africana J.C. Krug, Mycologia 80: 416. 1988. [Basionym]

Notes

Microthecium africanum is characterized by ostiolate ascomata and punctate, ellipsoidal ascospores. Two asexual morphs with different conidia have been reported: (i), 1–4(–5)-celled, globose and smooth-walled at first but becoming cylindrical and coarsely verrucose later; (ii), 1–2-celled, large, usually cylindrical and smooth-walled (Krug 1988). However, the type strain was probably not a pure culture because the SSU and LSU sequences match with different species of Fusarium and the pictures of the conidia type (i) resemble the chlamydospores produced by several species of this genus.

Microthecium beatonii D. Hawksw., Trans. Mycol. Soc. Japan 18: 145. 1977.

Sphaerodes beatonii (D. Hawksw.) P.F. Cannon & D. Hawksw., Bot. J. Linn. Soc. 84: 145. 1982.

Notes

This species is characterized by non-ostiolate ascomata, 4-spored asci and very coarsely reticulate, citriform ascospores. These morphological features are also observed in Microthecium perplexum, but this species produces ascospores with only a third of the surface coarsely reticulate while the rest remains smooth-walled. Microthecium episphaerium and Mi. retisporum differ from Mi. beatonii in the production of 8-spored asci. Moreover, Mi. retisporum produces a phialidic asexual morph and bulbils, which are absent in the other mentioned species, and smaller ascospores (17–20 × 10–12 × 7–9 µm) than in Mi. beatonii [28–34(–40) × 14–18(–20) µm], in Mi. episphaerium (25–34 × 12–18 µm) and in Mi. perplexum (22–28 × 12–15 × 9–11 µm).

Microthecium brevirostratum (Moreau) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812089

Melanospora brevirostrata Moreau, Bull. Trimest. Soc. mycol. Fr. 61: 59. 1945. [Basionym]

Notes

Microthecium brevirostratum together with Mi. fayodii and Mi. pegleri produces ostiolate ascomata, smooth-walled, ellipsoidal to navicular or citriform ascospores and bulbils. Microthecium brevirostratum is easily distinguished by ascospores with apiculate germ pores and the presence of a phialidic asexual morph (ascospores show depressed germ pores and lack an asexual morph in other species). Microthecium fayodii and Mi. pegleri differ in the size of the ascospores, Mi. pegleri having the smallest ascospores in Microthecium [(9.5–)11–12(–13) × 4–4.5 µm].

Microthecium brevirostrum (Fuckel) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812090

Ceratostoma brevirostre Fuckel, Bot. Ztg. 19: 250. 1861. [Basionym]

Melanospora brevirostris (Fuckel) Höhn., Sber. Akad. Wiss. Wien, Math.-naturw. Kl., Abt. 1 123: 94. 1914.

= Ceratostoma helvellae Cooke, Grevillea 1: 175. 1873.

Melanospora helvellae (Cooke) Sacc., Syll. fung. (Abellini) 2: 462. 1883.

= Melanospora sphaerodermoides Grove, J. Bot., Lond. 23: 132. 1885.

= Melanospora sphaerodermoides var. sphaerodermoides Grove, J. Bot., Lond. 23: 132. 1885.

= Thielavia soppittii Crossl., Naturalist, London: 7. 1901.

= Rosellinia aurea McAlpine, Fungus Diseases of stone-fruit trees in Australia: 102. 1902.

Sphaeroderma aureum (McAlpine) Sacc. & D. Sacc., Syll. fung. (Abellini) 17: 781. 1905.

Melanospora aurea (McAlpine) Doguet, Botaniste 39: 124. 1955.

= Melanospora sphaerodermoides var. rubella Pidopl., Mikrobiol. Zh. 9: 61. 1948.

= Melanospora camelina Faurel & Schotter, Revue Mycol., Paris 30: 144. 1965.

= Melanospora tulasnei Udagawa & Cain, Can. J. Bot. 47: 1932. 1970.

Notes

Microthecium brevirostrum, Mi. fallax and Mi. fimbriatum produce ostiolate ascomata and ellipsoidal to citriform, often plataniform, smooth-walled ascospores with an apiculate germ pore at each end. Microthecium fimbriatum is easily distinguished by its smaller (100–110 µm diam.), reddish ascomata, while Mi. fallax differs in the production of bulbils.

Microthecium ciliatum Udagawa & Takada, Trans. Mycol. Soc. Japan 15: 23. 1974.

Pteridiosperma ciliatum (Udagawa & Y. Takada) J.C. Krug & Jeng, Mycotaxon 10: 45. 1979.

Notes

This species is characterized by non-ostiolate ascomata and ellipsoidal to fusiform ascospores ornamented with wing-like appendages and wrinkles, and the production of a phialidic asexual morph and bulbils. Microthecium lenticulare and Mi. foveolatum also present ascospores with wing-like appendages, but these are pitted and not wrinkled (as in Mi. ciliatum), and neither species produces bulbils. Microthecium foveolatum and Mi. ciliatum are characterized by non-ostiolate ascomata and the production of a phialidic asexual morph, whereas Mi. lenticulare has ostiolate ascomata and lacks an asexual morph.

Microthecium compressum Udagawa & Cain, Can. J. Bot. 47: 1921. 1970.

Sphaerodes compressa (Udagawa & Cain) P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 145. 1982.

Notes

This species is distinguished by the production of non-ostiolate ascomata and citriform, bilaterally flattened ascospores, with the narrow faces coarsely reticulate and the widest faces smooth or nearly so, along with the production of a phialidic asexual morph.

Microthecium episphaerium (W. Phillips & Plowr.) Höhn., Sber. Akad. Wiss. Wien, Math.-naturw. Kl., Abt. 1 123: 98. 1914.

Melanospora episphaeria W. Phillips & Plowr., Grevillea 10: 71. 1881. [Basionym]

Sphaeroderma episphaerium (W. Phillips & Plowr.) Sacc., Syll. fung. (Abellini) 2: 460. 1883.

Sphaerodes episphaerium (W. Phillips & Plowr.) Clem. [as ‘episphaericum’], Gen. fung. (Minneapolis): 1‒227. 1909.

Vittadinula episphaeria (W. Phillips & Plowr.) Clem. & Shear, Gen. fung., Edn 2 (Minneapolis): 281. 1931.

= Sphaeroderma epimyces Höhn., Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften Math.-naturw. Klasse Abt. I 116: 103. 1907.

Melanospora epimyces (Höhn.) Doguet, Botaniste 39: 125. 1955.

Notes

Microthecium episphaerium shows non-ostiolate ascomata and very coarsely reticulate, citriform ascospores. For morphological comparison see Notes of Mi. beatonii.

Microthecium fallax (Zukal) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812772

Melanospora fallax Zukal, Sber. Akad. Wiss. Wien, Math.-naturw. Kl., Abt. 1 98: 547. 1889. [Basionym]

= Melanospora anomala Hotson, Proc. Amer. Acad. Arts & Sci 48.: 257. 1912.

= Melanospora cervicula Hotson, Proc. Amer. Acad. Arts & Sci. 48: 254. 1912.

= Melanospora papillata Hotson, Proc. Amer. Acad. Arts & Sci 48.: 251. 1912.

= Melanospora phaseoli Roll-Hansen, Blyttia 6: 73. 1948.

Notes

This species is characterized by ostiolate ascomata, ellipsoidal to citriform, often plataniform, smooth-walled ascospores, and production of bulbils. For morphological comparison see Notes of Mi. brevirostrum.

Microthecium fayodii (Vuill.) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812091
Fig. 5B, F, O

Melanospora fayodii Vuill. [as ‘fayodi’], Bull. Séanc. Soc. Sci. Nancy, Sér. 2 8: 33. 1887. [Basionym]

Notes

This species is characterized by ostiolate ascomata, ellipsoidal to navicular or citriform, smooth-walled ascospores, and production of bulbils. For morphological comparison see Notes of Mi. brevirostratum.

Microthecium fimbriatum (Rostr.) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812092

Sphaeroderma fimbriatum Rostr., Oest. Grönl. Svampe: 25. 1894. [Basionym]

Melanospora fimbriata (Rostr.) Petch, Trans. Br. mycol. Soc. 21: 253. 1938.

Notes

Microthecium fimbriatum produces ostiolate ascomata, and citriform to plataniform, smooth-walled ascospores with a strongly apiculate and tuberculate germ pore at each end. Although the ascomata was described as small and reddish in the protologue, the strain included in this study (NBRC 8523) shows larger (250–380 µm diam.), orange-brown ascomata. Moreover, our isolate produces bulbils. For morphological comparison see Notes of Mi. brevirostrum.

Microthecium fimicola (E.C. Hansen) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812093
Fig. 5C, M, P

Melanospora fimicola E.C. Hansen, Vidensk. Meddel. Dansk Naturhist. Foren. Kjøbenhavn 59: 15. 1876. [Basionym]

Sphaeroderma fimicola (E.C. Hansen) Sacc., Syll. fung. (Abellini) 2: 460. 1883.

Sphaerodes fimicola (E.C. Hansen) P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 146. 1982.

= Melanospora ornata Zukal, Verh. zool.-bot. Ges. Wien 35: 340. 1886.

Sphaerodes ornata (Zukal) Arx, Gen. Fungi Sporul. Cult., Edn 3 (Vaduz): 156. 1981.

= Sphaeroderma hulseboschii Oudem., Contrib. Flora Mycol. d. Pays-Bas 11: 23. 1886.

Melanospora hulseboschii (Oudem.) Doguet, Botaniste 39: 121. 1955.

= Melanospora affine Sacc. & Flageolet, Bull. Soc. Mycol. Fr. 12: 67. 1896.

= Melanospora manginii Vincens [as ‘mangini’], Bull. Soc. Mycol. Fr. 33: 69. 1917.

Sphaerodes manginii (Vincens) Arx, Gen. Fungi Sporul. Cult., Edn 3 (Vaduz): 156. 1981.

Notes

Microthecium fimicola is characterized by ostiolate ascomata and coarsely reticulate ascospores with strongly apiculate germ pores at both ends. The other species with ostiolate ascomata and reticulate ascospores are Mi. internum and Mi. quadrangulatum. The main differences among them are the shape and size of the ascospores, being citriform in Mi. fimicola, spindle-shaped in Mi. internum and fusiform in Mi. quadrangulatum. The production of bulbils has only been observed in our fresh isolates of Mi. fimicola, although this was not previously reported.

Microthecium foveolatum Udagawa & Y. Horie, in Hawksworth & Udagawa, Trans. Mycol. Soc. Japan 18: 149. 1977.

Pteridiosperma foveolatum (Udagawa & Y. Horie) J.C. Krug & Jeng, Mycotaxon 10: 45. 1979.

Notes

This species is easily distinguished by its non-ostiolate ascomata, ellipsoidal to fusiform ascospores ornamented with small pores and thick wing-like ridges usually longitudinal but often oblique, and production of phialidic asexual morph. For morphological comparison see Notes of Mi. ciliatum.

Microthecium fusisporum (Petch) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812094

Sphaeroderma fusisporum Petch, Naturalist, London: 58. 1936. [Basionym]

Melanospora fusispora (Petch) Doguet, Botaniste 39: 215. 1955.

= Melanospora fusispora var. fusispora (Petch) Doguet, Botaniste 39: 215. 1955.

= Melanospora fusispora var. parvispora Matsush., Matsush. Mycol. Mem. 8: 24. 1995.

Notes

Microthecium fusisporum is related to Mi. nectrioides, both possessing ostiolate ascomata and smooth-walled ascospores. However, Mi. nectrioides can be distinguished by the absence of the crown of setae around the ostiole and its citriform ascospores, being fusiform in Mi. fusisporum.

Microthecium geoporae (W. Oberm.) Höhn., Sber. Akad. Wiss. Wien, Math.-naturw. Kl., Abt. 1 123: 98. 1914.

Guttularia geoporae W. Oberm., Mykol. Zentbl. 3: 9. 1913. [Basionym]

Notes

This species produces non-ostiolate ascomata and citriform, smooth-walled ascospores. Other species previously placed in Melanospora characterized by the production of non-ostiolate ascomata and smooth-walled ascospores are Mi. hypomyces, Mi. levitum and Mi. zobelii. Microthecium hypomyces is distinguished by its fusiform ascospores (citriform in the other species), and Mi. levitum by the presence of bulbils and a phialidic asexual morph. Microthecium geoporae and Mi. zobelii are distinguished by the size of their ascospores [28–30 × 12–13(–15) µm in Mi. geoporae and 18–25 × 8.5–12 × 6–9 µm in Mi. zobelii]. Microthecium tenuissimum shows similar morphological features to these species but its ascospores are finely reticulate under SEM and its ascomata are smaller (less than 120 µm) than in the other species.

Microthecium hypomyces (Höhn.) Höhn., Sber. Akad. Wiss. Wien, Math.-naturw. Kl., Abt. 1 123: 50. 1914.

Sphaeroderma hypomyces Höhn., Sber. Akad. Wiss. Wien, Math.-naturw. Kl., Abt. 1 116: 102. 1907. [Basionym]

Melanospora hypomyces (Höhn.) Doguet, Botaniste 39: 215. 1955.

Notes

This species is characterized by non-ostiolate ascomata and fusiform, smooth-walled ascospores. For morphological comparison see Notes of Mi. geoporae.

Microthecium internum (Tehon & G.L. Stout) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812095

Melanospora interna Tehon & G.L. Stout, Mycologia 21: 181. 1929. [Basionym]

Notes

This species produces ostiolate ascomata and spindle-shaped ascospores with a coarse and irregular reticulum. For morphological comparison see Notes of Mi. fimicola.

Microthecium japonicum (Y. Horie, Udagawa & P.F. Cannon) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812096
Fig. 5I, J

Persiciospora japonica Y. Horie, Udagawa & P.F. Cannon, Mycotaxon 25: 233. 1986. [Basionym]

Notes

Microthecium japonicum is characterized by ostiolate ascomata and ellipsoidal to fusiform, punctate-reticulate ascospores, similar to Mi. moureai. However, Mi. japonicum produces a phialidic asexual morph and bulbils (absent in Mi. moureai) and delicately reticulate ascospores (coarsely reticulate in Mi. moureai).

Microthecium lenticulare (Udagawa & T. Muroi) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812097

Pteridiosperma lenticulare Udagawa & T. Muroi [as ‘lenticularis’], Trans. Mycol. Soc. Japan 22: 20. 1981. [Basionym]

Notes

Microthecium lenticulare produces ostiolate ascomata and pitted-walled ascospores with wing-like appendages. For morphological comparison see Notes of Mi. ciliatum.

Microthecium levitum Udagawa & Cain, Can. J. Bot. 47: 1917. 1970.

Fig. 5A, E, G, K

Sphaerodes levita (Udagawa & Cain) D. García, Stchigel & Guarro, Stud. Mycol. 50: 67. 2004.

Notes

This species is characterized by non-ostiolate ascomata, citrifrom and smooth-walled ascospores with umbonate and tuberculate germ pores, presence of bulbils and phialidic asexual morph. For morphological comparison see Notes of Mi. geoporae.

Microthecium marchicum (Lindau) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812099

Chaetomium marchicum Lindau, Hedwigia 35: 56. 1896. [Basionym]

Sphaeroderma marchicum (Lindau) Sacc. & P. Syd., Syll. fung. (Abellini) 14: 627. 1899.

Notes

Microthecium marchicum is characterized by its ostiolate ascomata and citrifrom, smooth-walled ascospores. Its ascospores are similar to those of Mi. geoporae, Mi. hypomyces, Mi. levitum and Mi. zobelii, but all of them produce non-ostiolate ascomata.

Microthecium masonii (Kirschst.) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812100

Ceratostoma masonii Kirschst., Trans. Br. mycol. Soc. 18: 306. 1934. [Basionym]

Persiciospora masonii (Kirschst.) P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 135. 1982.

Notes

Microthecium masonii is characterized by ostiolate ascomata and ellipsoidal to fusiform, faintly striate-reticulate ascospores. The same type of ascospore ornamentation is also observed in Mi. micropertusum, but this latter species is easily distinguished by the presence of inconspicuous ridges forming a very coarse reticulum and a phialidic asexual morph.

Microthecium micropertusum (Y. Horie, Udagawa & P.F. Cannon) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812101

Sphaerodes micropertusa Y. Horie, Udagawa & P.F. Cannon, Mycotaxon 25: 236. 1986. [Basionym]

Notes

Microthecium micropertusum is distinguished by its ostiolate ascomata, fusiform to citriform or nearly rhombic in outline ascospores with inconspicuous ridges forming a coarse reticulum, and presence of phialidic asexual morph. For morphological comparison see Notes of Mi. masonii.

Microthecium moreaui (P.F. Cannon & D. Hawksw.) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812102

Persiciospora moreaui P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 134. 1982. [Basionym]

Notes

Microthecium moreaui is characterized by its ostiolate ascomata, ellipsoidal and pitted-walled ascospores, and production of bulbils. For morphological comparison see Notes of Mi. japonicum.

Microthecium nectrioides (Marchal) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812103

Sphaeroderma nectrioides Marchal, Bull. Soc. R. Bot. Belg. 23: 25. 1884. [Basionym]

Melanospora nectrioides (Marchal) Doguet, Botaniste 39: 121. 1955.

= Melanospora asparagi G. Arnaud, Ann. Serv. Epiph. 2: 273. 1915.

Notes

This species produces ostiolate ascomata and citriform, smooth-walled ascospores. For morphological comparison see Notes of Mi. fusisporum.

Microthecium pegleri (D. Hawksw. & A. Henrici) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812104

Melanospora pegleri D. Hawksw. & A. Henrici, Kew Bull. 54: 795. 1999. [Basionym]

Notes

Microthecium pegleri is characterized by ostiolate ascomata, ellipsoidal to plano-convex, smooth-walled ascospores and presence of bulbils. For morphological comparison see Notes of Mi. brevirostratum.

Microthecium perplexum D. Hawksw., Trans. Mycol. Soc. Japan 18: 151. 1977.

Sphaerodes perplexa (D. Hawksw.) P.F. Cannon & D. Hawksw., Bot. J. Linn. Soc. 84: 148. 1982.

Notes

This species produces non-ostiolate ascomata, 4-spored asci and citrifrom ascospores usually with smooth walls, but one third of these are coarsely reticulated. For morphological comparison see Notes of Mi. beatonii.

Microthecium quadrangulatum (D. García, Stchigel & Guarro) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812105
Fig. 5D, L

Sphaerodes quadrangularis D. García, Stchigel & Guarro, Stud. Mycol. 50: 64. 2004. [Basionym]

Notes

Microthecium quadrangulatum is characterized by ostiolate ascomata and fusiform, reticulate ascospores with strongly apiculate germ pores. For morphological comparison see Notes of Mi. fimicola.

Microthecium retisporum Udagawa & Cain, Can. J. Bot. 47: 1926. 1970.

Fig. 5H, N

Sphaerodes retispora (Udagawa & Cain) P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 149. 1982.

= Microthecium retisporum var. inferius Udagawa & Cain [as ‘inferior’], Can. J. Bot. 47: 1928. 1970.

Sphaerodes retispora var. inferior (Udagawa & Cain) P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 149. 1982.

Sphaerodes inferior (Udagawa & Cain) D.W. Li & N.P. Schultes, in Schultes, Murtishi & Li, Fungal Biology 121: 901. 2017.

= Microthecium retisporum var. retisporum Udagawa & Cain, Can. J. Bot. 47: 1926. 1970.

Sphaerodes retispora var. retispora (Udagawa & Cain) P.F. Cannon & D. Hawksw., J. Linn. Soc., Bot. 84: 149. 1982.

Notes

This species is characterized by non-ostiolate ascomata, reticulate citriform ascospores with apiculate germ pores, a phialidic asexual morph and presence of bulbils. For morphological comparison see Notes of Mi. beatonii.

Microthecium sepedonioides (Preuss) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812106
Fig. 5Q

Papulaspora sepedonioides Preuss, Linnaea 24: 112. 1851. [Basionym]

Notes

Microthecium sepedonioides only produces bulbils and the sexual morph has never been observed.

Microthecium tenuissimum (D. García, Stchigel & Guarro) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812107

Sphaerodes tenuissima D. García, Stchigel & Guarro, Stud. Mycol. 50: 65. 2004. [Basionym]

Notes

This species is characterized by non-ostiolate ascomata and citriform, ellipsoidal in lateral view, finely reticulate ascospores with strongly apiculate germ pores. For morphological comparison see Notes of Mi. geoporae.

Microthecium zobelii Corda, Icon. fung. (Prague) 5: 74. 1842.

Sphaeria zobelii (Corda) Tul. & C. Tul., Fungi hypog.: 186. 1851.

Ceratostoma zobelii (Corda) Berk., Journal of the Royal Horticultural Society 4: 402. 1860.

Melanospora zobelii (Corda) Fuckel, Jb. nassau. Ver. Naturk. 23-24: 127. 1870.

= Melanospora zobelii var. zobelii (Corda) Fuckel, Jb. nassau. Ver. Naturk. 23-24: 127. 1870.

= Melanospora coprophila Zukal, Sber. Akad. Wiss. Wien, Math.-naturw. Kl., Abt. 1 98: 544. 1889.

= Melanospora marchicum Lindau, Hedwigia 35: 56. 1896.

= Melanospora zobelii var. minor Pidopl., Mikrobiol. Zh. 9(2-3): 60. 1948.

Notes

Microthecium zobelii produces non-ostiolate ascomata, and citriform, smooth-walled ascospores with slightly apiculate germ pores. For morphological comparison see Notes of Mi. geoporae.

Doubtful species

Microthecium ryvardenianum Aramb. & Gamundí, Agarica 6: 124. 1985.

Notes

This species is considered as doubtful because it presents morphological features atypical of Microthecium (e.g. allantoid ascospores when immature becoming striate when mature).

Pseudomicrothecium Y. Marín, Stchigel, Guarro, Cano, gen. nov .

MycoBank No: 812108

Type species

Pseudomicrothecium subterraneum (L. Fan, C.L. Hou, P.F. Cannon & Yong Li) Y. Marín, Stchigel, Guarro & Cano. Holotype and ex-isotype strain: BJTC FAN1001, K[M] 172128.

Description

Ascomata non-ostiolate, globose, translucent, pale brown to brown, appearing dark brown when the ascospores are mature, glabrous or setose; ascomatal wall membranaceous, of textura angularis. Asci 2-spored, clavate, short-stipitate, without apical structures, evanescent. Ascospores one-celled, at first hyaline, becoming dark brown to blackish when mature, ellipsoidal to citriform, umbonate and truncate at both ends, with a terminal indistinct germ pore at each end. Asexual morph absent.

Etymology

The name refers to the morphological resemblance to Microthecium.

Notes

The new genus Pseudomicrothecium is proposed here to accommodate Melanospora subterranea because it constitutes a separate lineage in our phylogenetic study. This genus is characterized by its non-ostiolate ascomata, similar to those of Microthecium, 2-spored asci and smooth-walled ascospores with an indistinct germ pore at each end. Asci containing two ascospores have only been observed in some species of Scopinella (i.e. Scopinella gallicola and S. sphaerophila). However, Scopinella can be easily distinguished from Pseudomicrothecium by the production of ostiolate ascomata with long necks and cuboid-ellipsoidal ascospores with two prominent longitudinal germ slits.

Pseudomicrothecium subterraneum (L. Fan, C.L. Hou, P.F. Cannon & Yong Li) Y. Marín, Stchigel, Guarro & Cano, comb. nov.

MycoBank No: 812109

Basionym

Melanospora subterranea L. Fan, C.L. Hou, P.F. Cannon & Yong Li, Mycologia 104: 1434. 2012.

Discussion

We have revised the taxonomy of relevant members of the family Ceratostomataceae based on the analyses of the SSU, LSU, ITS, act and tef1 nucleotide sequences. This study strongly supported the order Melanosporales proposed by Zhang and Blackwell in 2007 (Hibbett et al. 2007). The phylogenetic inference showed seven lineages corresponding to the genera Dactylidispora, Echinusitheca, Melanospora, Microthecium, Pseudomicrothecium and Vittatispora, and to Melanospora kurssanoviana. Our results agree with previous studies (Zhang and Blackwell 2002, Fan et al. 2012) which already suggested and demonstrated that the ornamentation of the ascospores under SEM, a feature traditionally used to delimit most of the genera in the Melanosporales, is not useful for estimating phylogenetic relationships among these fungal taxa. Similarly, the morphology of the ascospores is of weak taxonomic value and a poor predictor for the generic delimitation of members of the family Sordariaceae, resulting in the synonymy of two relevant genera, i.e. Gelasinospora and Neurospora (Dettman et al. 2001, García et al. 2004, Nygren et al. 2011). In our study, two of the largest genera of the Melanosporales, Melanospora and Microthecium, grouped species with both smooth and ornamented ascospore walls. By contrast, a phylogenetic study of the Lasiosphaeriaceae (Miller and Huhndorf 2005) revealed that the morphology of the ascomatal wall was more phylogenetically informative than that of the ascospores, with several new genera proposed (i.e. Immersiella) or emended (i.e. Lasiosphaeria, Lasiosphaeris and Schizothecium) (Miller and Huhndorf 2004, Cai et al. 2005). Here, the erection of the new genus Echinusitheca is a clear example of the relevance of the ascomatal morphology in the taxonomy of these fungi, and in fact this taxon together with Arxiomyces and Scopinella are the only genera in the Melanosporales that show dark semi-transluscent ascomata. In this context, although Echinusitheca has ascospores similar to those of Melanospora and Microthecium, this genus constitutes one of the lineages phylogenetically most distant within this order.

Another lineage considerably distant from the other members of the Melanosporales is constituted by the clade represented only by the species Melanospora kurssanoviana, suggesting that this fungus could represent a new genus. However, this new taxon is at this moment not proposed because its colonies, in spite of attempts to induce sporulation, remain sterile and a detailed morphological study was not possible. The infertility of the cultures is probably due to the fact that an important part of the members of this fungal group show a peculiar habitat developing a certain degree of mycoparasitism and requiring the presence of the host to complete the biologic cycle and develope reproductive structures. The mycoparasitism of Melanospora, Syspastospora and the species previously placed in Persiciospora and Sphaerodes has already been demonstrated by numerous authors (Doguet 1955, Calviello 1973, Jordan and Barnett 1978, Harveson and Kimbrough 2000, 2001), and this ability has been exploited in the biocontrol of phytopathogenic fungi (Vujanovic and Goh 2009, Goh and Vujanovic 2010, Kim and Vujanovic 2016, 2017).

The genus Sphaeronaemella, which is characterized by pale and translucent ascomata, was thought to be related to Melanospora (Cannon and Hawksworth 1982). However, we do not agree with this relationship because it differs from the Melanosporales in the production of hyaline ascospores, as opposed to the pigmented ones in the members of that order. By contrast, our results correlate with those of other authors that demonstrated a closer phylogenetic relationship of this genus with the members of the order Microascales (Spatafora and Blackwell 1994b, Hausner and Reid 2004). In fact, our SSU tree seems to indicate that Sphaeronaemella could represent a new family of the Microascales; however, further studies including more taxa and additional genes are needed to more accurately confirm its taxonomic status.

The placement of our isolate of Persiciospora japonicum in the Microthecium clade once more demonstrated that the ornamentation of the ascospores, which is pitted in Persiciospora spp., is of poor taxonomic value, and consequently all the species of Persiciospora should be transferred to Microthecium. As it was above mentioned, the species of this latter genus show a typical cellular ascomatal neck which is also present in Persiciospora and constitutes a common feature in both genera. Surprisingly, in some previous phylogenetic studies, the species of Persiciospora were placed in the Hypocreales, closely related to Nectria (Zhang and Blackwell 2002, Maharachchikumbura et al. 2015, Schultes et al. 2017). However, this could be probably explained by a possible contamination of the cultures of Persiciospora spp. with an hypocrealean host (Fan et al. 2012). The same situation may have occurred with the cultures of Scopinella and Syspastospora, which led to a possible erroneous classification of both taxa in the Hypocreales (Zhang and Blackwell 2002, Chaudhary et al. 2006, Fan et al. 2012, Maharachchikumbura et al. 2015, Schultes et al. 2017).

Pteridiosperma ciliatum, a member of the Melanosporales with ascospores ornamented with longitudinal wing-like ridges that anastomose each other to form a well defined reticulum (a distinctive feature of Pteridiosperma), was also found in the Microthecium clade, proving once again that the ascospore ornamentation is not phylogenetically informative. Consequently, we have synonymyzed the genus Pteridiosperma with Microthecium since Pteridiosperma spp. show non-ostiolate ascomata, or if ostiolate, they show a short neck composed of angular cells, which are typical morphological characteristics of Microthecium.

Another genus that our results demonstrated should be synonymized and included in Microthecium is Sphaerodes because its type species, S. episphaerium, shows morphological features (non-ostiolate ascomata) that fit with the current circumscription of that emended genus. Most of the species of Sphaerodes, with the exception of S. ellipsospora and S. singaporensis, which are now located in the new genus Dactylidispora, and S. mycoparasitica, which is now placed in Melanospora, are also transferred to Microthecium since these produce non-ostiolate or ostiolate ascomata without a neck, or less frequently with a short neck composed of angular cells similar to the ascomatal ones. Another relevant feature of the genus Microthecium is the production of bulbils. These propagules are typical of Papulaspora, an anamorphic genus that encompasses more than 40 species. Although it was initially accepted as a genus without a sexual morph (Hotson 1912), its link with species of Melanospora and Chaetomium has been reported (Roll-Hansen 1948, Zhang et al. 2004). In our phylogenetic study Papulaspora sepedonioides, the type species of the genus, was nested in the Microthecium clade, and therefore transferred to this genus. The relationship of this species with the Melanosporales had already previously been demonstrated by Davey et al. (2008) and Li et al. (2016). However, it has been demonstrated that Papulaspora is a polyphyletic genus, and other species of the genus have been reported as belonging to the classes Leotiomycetes and Sordariomycetes (Ascomycota). Therefore, the other species of Papulaspora not linked to the species of Microthecium should be transferred to other taxonomic groups. The relationship of some species of Papulaspora with the Melanosporales is also suggested by the production of similar phialidic synanamorphs (Van Beyma 1931, Hotson 1942).

The most recent new combination performed in Sphaerodes, S. inferior, was done to accommodate S. retispora var. inferior since it was not clustering with S. retispora var. retispora (Schultes et al. 2017). However, we suspected that the sequences of S. retispora var. retispora deposited in GenBank were contaminated with the hypocrealean host. In order to corroborate it, we studied such sequenced strain demonstrating that it was effectively contaminated. Therefore, S. inferior is here considered a synonym of Mi. retisporum since the morphological differences are insufficient to recognize this variety as a different species.

There are important morphological differences among the strains of Microthecium that suggest the presence of several additional cryptic species in the genus; however, our phylogenetic study, in spite of having used five loci, was not able to resolve the boundaries among them.

Acknowledgments

This work was supported by the Spanish “Ministerio de Economía y Competitividad”, grant CGL2017-88094-P. The new genus Echinusitheca was recovered from samples collected during fieldwork supported by a National Science Foundation grant (DEB-0515558) to ANM.

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