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Four new corticioid species in Trechisporales (Basidiomycota) from East Asia and notes on phylogeny of the order
expand article infoShi-Liang Liu, Hai-Xia Ma§, Shuang-Hui He, Yu-Cheng Dai
‡ Beijing Forestry University, Beijing, China
§ Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, China
Open Access

Abstract

Four new species in Trechisporales from East Asia, Dextrinocystis calamicola, Subulicystidium acerosum, S. tropicum and Tubulicium bambusicola, are described and illustrated, based on morphological and molecular evidence. The phylogeny of Trechisporales was inferred from a combined dataset of ITS-nrLSU sequences. In the phylogenetic tree, Sistotremastrum formed a family-level clade of its own, sister to the Hydnodontaceae clade formed by all other genera. Dextrinocystis, is for the first time, confirmed as a member of Hydnodontaceae. A key to all the accepted genera in Trechisporales is given.

Keywords

Hydnodontaceae, Sistotremastrum family, phylogeny, taxonomy, wood-inhabiting fungi

Introduction

Trechisporales K.H. Larss. is a rather small but strongly supported order in Agaricomycotina (Hibbett et al. 2007; Larsson 2007). At present, eight to twelve genera, Brevicellicium K.H. Larss. & Hjortstam, Fibriciellum J. Erikss. & Ryvarden, Fibrodontia Parmasto, Luellia K.H. Larss. & Hjortstam, Porpomyces Jülich, Subulicystidium Parmasto, Trechispora P. Karst. (type genus, including Cristelloporia I. Johans. & Ryvarden, Echinotrema Park-Rhodes, Hydnodon Banker and Scytinopogon Singer) and Tubulicium Oberw., are placed in the family Hydnodontaceae, while Sistotremastrum J. Erikss. should be placed in a family of its own (Larsson 2001, 2007; Larsson et al. 2004; Binder et al. 2005; Hibbett et al. 2007, 2014; Birkebak et al. 2013; Telleria et al. 2013a). In addition, four genera, Dextrinocystis Gilb. & M. Blackw., Dextrinodontia Hjortstam & Ryvarden, Brevicellopsis Hjortstam & Ryvarden and Litschauerella Oberw. were listed as possible candidates of Hydnodontaceae waiting for molecular confirmation (Larsson 2007; Hibbett et al. 2014). Except for Scytinopogon and Trechispora thelephora (Lév.) Ryvarden, all the taxa in Trechisporales have resupinate basidiomata and most of them have a non-poroid hymenophore (Fig. 1, Albee-Scott and Kropp 2011; Hibbett et al. 2014). However, the microscopic characters vary significantly amongst different genera and some of them were surprisingly placed in the order solely based on molecular phylogeny (Larsson 2007; Bernicchia and Gorjón 2010).

Figure 1. 

Basidiomata of Trechisporales. a Scytinopogon pallescens (Bres.) Singer (He 5192) b Porpomyces submucidus F. Wu & C.L. Zhao (Dai 13708) c Fibrodontia alba Yurchenko & Sheng H. Wu (He 4761) d Trechispora sp. (He 5491) e Subulicystidium sp. (He 3048) f Tubulicium raphidisporum (Boidin & Gilles) Oberw., Kisim.-Hor. & L.D. Gómez (He 3191). Scale bar: 1 cm.

Except for Trechispora, the largest genus in the order, most genera in Trechisporales have mostly few species and some are still monotypic. However, in recent years, many new species have been described, based on both DNA sequence data and morphological characters. Wu et al. (2015) described a cryptic species of Porpomyces mucidus (Pers.) Jülich, based mainly on sequence data. Ordynets et al. (2018) studied the short-spored species of Subulicystidium and recognised eleven new species. Tens specimens of Trechisporales were collected from East Asia by the senior authors in the past three years. The purposes of the present paper are to study these specimens by using morphological and molecular methods and discuss the phylogeny of the Trechisporales, based on expanded sampling.

Materials and methods

Morphological studies

Voucher specimens were deposited in the herbaria of Beijing Forestry University, Beijing, China (BJFC) and in the Centre for Forest Mycology Research, U.S. Forest Service, Madison, USA (CFMR). Freehand sections were made from dried basidiomata and mounted in 0.2% cotton blue in lactic acid, 1% phloxine (w/v) or Melzer’s reagent. Microscopic examinations were carried out with a Nikon Eclipse 80i microscope (Nikon Corporation, Japan) at magnifications up to 1000×. Drawings were made with the aid of a drawing tube. All measurements were carried out with sections mounted in Melzer’s reagent. The following abbreviations are used: L = mean spore length, W = mean spore width, Q = L/W ratio, n (a/b) = number of spores (a) measured from given number of specimens (b). Colour names and codes follow Kornerup and Wanscher (1978).

DNA extraction and sequencing

The CTAB plant genome rapid extraction kit DN14 (Aidlab Biotechnologies Co. Ltd, Beijing) was used for DNA extraction and PCR amplification from dried specimens. The ITS1-5.8S-ITS2 and partial nrLSU markers were amplified with the primer pairs ITS5/ITS4 (White et al. 1990) and LR0R/LR7 (Vilgalys and Hester 1990). The PCR procedures followed Liu et al. (2017). DNA sequencing was performed at Beijing Genomics Institute and the sequences were deposited in GenBank (Benson et al. 2018). The sequence quality control followed Nilsson et al. (2012). BioEdit v.7.0.5.3 (Hall 1999) and Geneious v.11.1.15 (Kearse et al. 2012) were used for chromatogram check and contig assembly.

Phylogenetic analyses

The molecular phylogeny was inferred from a combined dataset of ITS1-5.8S-ITS2-nrLSU sequences of Trechisporales sensu Larsson (2007) (Table 1). Hyphodontia floccosa (Bourdot & Galzin) J. Erikss. and H. subalutacea (P. Karst.) J. Erikss. were selected as the outgroup (Wu et al. 2015). The sequences of ITS and nrLSU were aligned separately using MAFFT v.7 (Katoh et al. 2017, http://mafft.cbrc.jp/alignment/server/) with the G-INS-i iterative refinement algorithm. The separate alignments were concatenated using Mesquite v.3.5.1 (Maddison and Maddison 2018). The combined alignments were deposited in TreeBase (http://treebase.org/treebase-web/home.html, submission ID: 23620).

Species and sequences used in the phylogenetic analyses.

Taxa Voucher Locality ITS nrLSU Reference
Brevicellicium exile MA-Fungi 26554 Spain HE963777 HE963778 Telleria et al. (2013a)
B. olivascens MA-Fungi 41366 Spain HE963785 HE963786 Telleria et al. (2013a)
B. sp MPM 2012 Portugal HE963774 Telleria et al. (2013a)
Dextrinocystis calamicola BJFC: He 5693 China MK204533 MK204546 This study
D. calamicola BJFC: He 5700 China MK204534 MK204547 This study
BJFC: He 5701 China MK204548 This study
Fibrodontia alba TNM: F25503 Taiwan JQ612713 JQ612714 Yurchenko and Wu (2014)
F. alba BJFC: He 4761 China MK204529 MK204541 This study
F. brevidens TNM: Wu 9807-16 Taiwan KC928276 KC928277 Yurchenko and Wu (2014)
BJFC: He 3559 China MK204528 This study
F. gossypina AFTOL-ID 599 DQ249274 AY646100 Unpublished
Hyphodontia floccosa GB: Berglund 150-02 Sweden DQ873618 DQ873617 Larsson et al. (2006)
H. subalutacea GEL 2196 DQ340341 DQ340362 Unpublished
Litschauerella sp. BJFC: He 3171 China MK204555 MK204556 This study
Porpomyces mucidus BJFC: Dai 12692 Czech Republic KT157833 KT157838 Wu et al. (2015)
P. submucidus BJFC: Cui 5183 China KT152143 KT152145 Wu et al. (2015)
Subulicystidium boidinii KAS: L 1584a Reunion MH041527 Ordynets et al. (2018)
S. acerosum BJFC: He 3804 China MK204539 MK204543 This study
S. brachysporum O: F: KHL 16100 Brazil MH000599 MH000599 Ordynets et al. (2018)
BJFC: He 2207 USA MK204532 MK204549 This study
S. fusisporum GB: KHL 10360 Puerto Rico MH041535 MH041567 Ordynets et al. (2018)
S. grandisporum O: F: 506781 Costa Rica MH041547 MH041592 Ordynets et al. (2018)
S. harpagum KAS: L 1726a Reunion MH041532 MH041588 Ordynets et al. (2018)
S. inornatum GB: KHL 10444 Puerto Rico MH041558 MH041569 Ordynets et al. (2018)
S. longisporum GB: KHL 14229 Sweden MH000601 MH000601 Ordynets et al. (2018)
BJFC: He 2981 China MK204550 This study
S. meridense GB: Hjm 16400 Brazil MH041538 MH041604 Ordynets et al. (2018)
S. nikau KAS: L 1296 Reunion MH041513 MH041565 Ordynets et al. (2018)
S. obtusisporum FR: Piepenbrink & Lotz-Winter W213-3-I Germany MH041521 MH041566 Ordynets et al. (2018)
S. parvisporum KAS: L 0140 Reunion MH041529 MH041590 Ordynets et al. (2018)
S. perlongisporum TU 124388 Italy UDB028355 UDB028355 Kõljalg et al. (2013)
GB: KHL 16062 Brazil MH000600 MH000600 Ordynets et al. (2018)
S. rarocrystallinum O: F: 918488 Colombia MH041512 MH041564 Ordynets et al. (2018)
S. robustius GB: KHL 10813 Jamaica MH041514 MH041608 Ordynets et al. (2018)
S. tedersooi TU 110894 Vietnam UDB014161 Kõljalg et al. (2013)
S. tropicum BJFC: He 3968 China MK204531 MK204544 This study
BJFC: He 3583 China MK204530 MK204542 This study
Scytinopogon angulisporus TFB 13611 USA JQ684661 Unpublished
S. havencampii SFSU: DED 8300 Príncipe island KT253946 KT253947 Desjardin and Perry (2015)
S. pallescens BJFC: He 5192 Vietnam MK204553 This study
Sistotremastrum guttuliferum MA-Fungi 82105 Portugal JX310445 Telleria et al. (2013b)
S. guttuliferum BJFC: He 3338 China MK204540 MK204552 This study
S. niveocremeum CBS 427.54 France MH857380 MH868920 Vu et al. (2019)
S. suecicum GB: KHL11849 Sweden EU118666 EU118667 Larsson (2007)
Trechispora alnicola AFTOL-ID 665 AY635768 Unpublished
T. araneosa GB: KHL 8570 Sweden AF347084 AF347084 Larsson et al. (2004)
T. bispora CBS 142.63 Australia MH858241 MH869842 Vu et al. (2019)
T. confinis GB: KHL 11064 Sweden AF347081 AF347081 Larsson et al. (2004)
T. farinacea TUB 011825 Germany EU909231 EU909231 Krause et al. (2011)
T. hymenocystis GB: KHL 8795 Sweden AF347090 AF347090 Larsson et al. (2004)
T. kavinioides GB: KGN 981002 Norway AF347086 AF347086 Larsson et al. (2004)
T. mollusca CBS 439.48 Canada MH856428 Vu et al. (2019)
T. nivea GB: G. Kristiansen Norway AY586720 Larsson et al. (2004)
Tubulicium bambusicola BJFC: He 4776 China MK204536 MK204551 This study
T. bambusicola BJFC: He 4058 Thailand MK204535 This study
T. raphidisporum BJFC: He 2851 China MK204538 MK204554 This study
BJFC: He 3191 China MK204537 MK204545 This study
T. vermiculare GEL 5015 AJ406424 Langer (2002)
T. vermiferum GB: KHL 8714 Norway AY463477 Larsson et al. (2004)

For both Maximum Likelihood (ML) and Bayesian Inference (BI), a partitioned analysis was performed with the following four partitions: ITS1, 5.8S, ITS2 and nrLSU. The ML analysis was performed using RAxML v.8.2.10 (Stamatakis 2014) with the bootstrap values (ML-BS) obtained from 1,000 replicates and the GTRGAMMA model of nucleotide evolution. The BI was performed using MrBayes 3.2.6 (Ronquist et al. 2012). The best-fit substitution model for each partitioned locus was estimated separately with jModeltest v.2.17 (Darriba et al. 2012) by restricting the search to models that can be implemented in MrBayes. Two runs of four Markov chains were run for 4,000,000 generations until the split deviation frequency value was lower than 0.01. The convergence of the runs was checked using Tracer v.1.7 (Rambaut et al. 2018). Trees and model parameters were sampled every 100th generation. The first quarter of the trees, which represented the burn-in phase of the analyses, was discarded and the remaining trees were used to build a majority rule consensus tree and to calculate Bayesian posterior probabilities (BPP). All trees were visualised in FigTree 1.4.2 (Rambaut 2014).

Results

Phylogenetic inference

The ITS-nrLSU sequence dataset contained 50 ITS and 51 nrLSU sequences from 58 samples representing 45 ingroup taxa and the outgroup (Table 1). Fourteen ITS and 15 nrLSU sequences were generated for this study. jModelTest suggested GTR+G, SYM+I+G, GTR+I+G and GTR+I+G to be the best-fit models of nucleotide evolution for ITS1, 5.8S, ITS2 and nrLSU markers, respectively, for the Bayesian analysis. BI analysis resulted in an almost identical tree topology compared to the ML analysis and no significant conflicts were found between the two analyses. Only the ML tree is shown in Fig. 2 with ML bootstrap values ≥ 50% and Bayesian posterior probabilities ≥ 0.95 labelled along the branches.

Figure 2. 

Phylogeny of Trechisporales inferred from ITS-nrLSU sequences. Topology is from ML analysis with maximum likelihood bootstrap support values (≥ 50, former) and Bayesian posterior probability values (≥ 0.95, latter) shown along the branches. Different genera are indicated as coloured blocks. The new species are set in bold. Scale bar: 0.2 nucleotide substitutions per site.

In the tree (Fig. 2), two large clades, corresponding to Hydnodontaceae and Sistotremastrum family, were strongly supported. Except for Sistotremastrum, the other eight genera sampled were nested within the Hydnodontaceae clade. The genera Brevicellicium, Fibrodontia, Porpomyces and Subulicystidium were strongly supported as monophyletic lineages. Dextrinocystis calamicola, the first species sequenced in the genus, formed a sister lineage to Tubulicium with relatively strong support (ML-BS = 78%, BPP = 1). The three species of Scytinopogon were nested within the Trechispora lineage. Subulicystidium acerosum and S. tropicum formed distinct lineages in the genus, while Tubulicium bambusicola is closely related to T. raphidisporum.

Taxonomy

Dextrinocystis calamicola S.H. He & S.L. Liu, sp. nov.

MycoBank No: 828718
Fig. 3

Typification

CHINA. Fujian Province, Wuyishan County, Wuyishan Nature Reserve, on dead culms of Calamus, 3 Oct 2018, He 5701 (holotype, BJFC 026763).

Etymology

calamicola” refers to growing on Calamus.

Basidiomata

Annual, resupinate, effused, thin, soft, easily separated from the substrate, at first as irregular small patches, later confluent up to 15 cm long, 2 cm wide. Hymenophore surface smooth, orange white (5A2) to greyish-orange [5B(3–5)], finely cracked with age; margin thinning out, fimbriate, slightly paler than hymenophore surface, becoming indistinct with age.

Microscopic structures

Hyphal system monomitic; generative hyphae with clamp connections, hyaline, thin-walled, frequently branched and septate, loosely interwoven, 2–3 µm in diam. Cystidia-like branches present, branched from subicular hyphae, embedded, hyaline, thick-walled, encrusted at apex, 20–30 × 1.5–2 µm. Hymenial cystidia abundant, subulate, projecting beyond hymenium, bi- or multi-rooted, hyaline, distinctly thick-walled with a narrow lumen, slightly encrusted at apex, distinctly dextrinoid, 50–110 × 5–6 µm. Basidia suburniform to subclavate, hyaline, thin-walled, with 4 sterigmata and a basal clamp connection, 20–30 × 5–8 µm; sterigmata mostly cylindrical with a blunt tip; basidioles in shape similar to basidia, but slightly smaller. Basidiospores abundant, oblong ellipsoid to short cylindrical, hyaline, thin-walled, smooth, negative in Melzer’s reagent, acyanophilous, (7–)7.5–8.8(–9) × (3.2–)3.3–4 µm, L = 8.1 µm, W = 3.7 µm, Q = 2.1–2.2 (n = 60/2).

Additional specimens examined

CHINA. Fujian Province, Wuyishan County, Wuyishan Nature Reserve, on dead culms of Calamus, 3 Oct 2018, He 5693 (BJFC 026755) & He 5700 (BJFC 026762).

Remarks

The thin whitish basidiomata on a palm tree, distinctly thick-walled cystidia with a dextrinoid reaction in Melzer’s reagent, presence of small cystidia-like branches and short cylindrical basidiospores indicate that the new species is a member of Dextrinocystis. Two species, D. capitata (D.P. Rogers & Boquiren) Gilb. & M. Blackw. and D. macrospora (Liberta) Nakasone have been reported in the genus, both of which differ from D. calamicola by having much larger basidiospores (11–14 × 3–4 µm for D. capitata in Gilbertson and Blackwell 1988; 12–19 × 4.5–7 µm for D. macrospora in Liberta 1960) and a distribution in America. In the phylogenetic tree, D. calamicola formed a sister lineage to Tubulicium with relatively strong support (Fig. 2).

Figure 3. 

Dextrinocystis calamicola (holotype, He 5701). a basidiomata b, f basidiospores c, g basidia d, h cystidia e, i cystidia-like branches in subiculum j subicular hyphae. Scale bars: 1 cm (a), 10 µm (b–j). b, c Taken in phloxine d, e taken in Melzer’s reagent.

Subulicystidium acerosum S.H. He & S.L. Liu, sp. nov.

MycoBank No: 828719
Fig. 4

Typification

CHINA. Guizhou Province, Libo County, Maolan Nature Reserve, on fallen angiosperm trunk, 16 Jun 2016, He 3804 (holotype, BJFC 022303).

Etymology

acerosum” refers to the presence of numerous needle-like crystals.

Basidiomata

Annual, resupinate, effused, very thin, easily separated from the substrate, up to 6 cm long, 2 cm wide. Hymenophore surface smooth, more or less arachnoid, white (5A1) to orange grey (5B2); margin undifferentiated.

Microscopic structures

Hyphal system monomitic; generative hyphae with clamp connections, hyaline, thin-walled, frequently branched and septate, loosely interwoven, 2–3.5 µm in diam. Cystidia abundant, subulate, projecting beyond hymenium, hyaline, thick-walled and regularly covered with rectangular crystals at basal part, thin-walled and smooth at apex part, 50–100 × 3–5 µm. Crystals numerous, distributed in whole section or more commonly attached on cystidia, acerose, hyaline. Basidia short clavate, hyaline, thin-walled, with 4 sterigmata and a basal clamp connection, 15–20 × 4–5.5 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores narrowly fusiform to slightly vermicular, hyaline, thin-walled, smooth, negative in Melzer’s reagent, acyanophilous, (14.5–)15.5–18(–20) × 1.8–2.2 µm, L = 16.6 µm, W = 2 µm, Q = 8.3 (n = 30/1).

Remarks

Subulicystidium acerosum is characterised by the long and narrow basidiospores and presence of numerous acerose crystals. The species is similar to S. longisporum (Pat.) Parmasto, which differs in having slightly shorter and wider basidiospores (12–16 × 2–3 µm, Q < 7, Ordynets et al. 2018). Subulicystidium cochleum Punugu is similar to S. acerosum by sharing needle-like crystals but differs in having larger basidiospores (20–27 × 2–3 µm, Punugu et al. 1980; Ordynets et al. 2018). Phylogenetically, S. acerosum is distinct from all the other sampled species of Subulicystidium (Fig. 2).

Figure 4. 

Subulicystidium acerosum (holotype, He 3804). a basidiomata b, f basidiospores c acerose crystals d, e, g cystidia h basidia and a basidiole. Scale bars: 1 cm (a), 10 µm (b–h). b–e Taken in phloxine.

Subulicystidium tropicum S.H. He & S.L. Liu, sp. nov.

MycoBank No: 828720
Fig. 5

Typification

CHINA. Hainan Province, Wuzhishan County, Wuzhishan Nature Reserve, on fallen angiosperm branch, 10 Jun 2016, He 3968 (holotype, BJFC 022470).

Etymology

tropicum” refers to the distribution in tropical areas.

Basidiomata

Annual, resupinate, effused, very thin, separable from the substrate, up to 10 cm long, 3 cm wide. Hymenophore surface smooth, white (5A1), orange grey (5B2) to greyish-orange [5B(3–4)], not cracked; margin undifferentiated.

Microscopic structures

Hyphal system monomitic; generative hyphae with clamp connections, hyaline, slightly thick-walled, frequently branched and septate, loosely interwoven, 2–3.5 µm in diam. Cystidia abundant, subulate, projecting beyond hymenium, hyaline, thick-walled and regularly covered with rectangular crystals except at the apex, 40–70 × 3–5 µm. Basidia subclavate to suburniform, hyaline, thin-walled, with 4 sterigmata and a basal clamp connection, 12–17 × 4–5 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores fusiform to slightly vermicular, hyaline, thin-walled, smooth, negative in Melzer’s reagent, acyanophilous, 11–12.5(–13) × 1.8–2.2 µm, L = 11.9 µm, W = 2 µm, Q = 5.95 (n = 30/1).

Additional specimens examined

CHINA. Hainan Province, Baoting County, Qixianling Forest Park, on fallen angiosperm branch, 18 Mar 2016, He 3583 (BJFC 022083).

Remarks

Subulicystidium tropicum resembles S. acerosum and S. perlongisporum Boidin & Gilles by sharing narrow basidiospores in the genus, but differs from S. acerosum in having shorter basidiospores and lacking the needle-like crystals and from S. perlongisporum in having much shorter basidiospores and a tropical distribution (16–25 × 1.5–2.5 µm for S. perlongisporum in Ordynets et al. 2018). The new species is also similar to S. longisporum, but differs in having slender basidiospores and a tropical distribution. In the phylogenetic tree, S. tropicum formed a distinct lineage in Subulicystidium (Fig. 2).

Figure 5. 

Subulicystidium tropicum (holotype, He 3968). a basidiomata b, d basidiospores c, e cystidia f basidia g subicular hyphae. Scale bars: 1 cm (a), 10 µm (b–g). b, c Taken in phloxine.

Tubulicium bambusicola S.H. He & S.L. Liu, sp. nov.

MycoBank No: 828721
Fig. 6

Typification

THAILAND. Chiang Rai Province, Doi Mae Salong, on dead culms of bamboo, 22 Jul 2016, He 4058 (holotype, BJFC 023499).

Etymology

bambusicola” refers to growing on bamboo.

Basidiomata

Annual, resupinate, effused, closely adnate, thin, at first as irregular small patches, later confluent up to 15 cm long, 5 cm wide. Hymenophore surface smooth, pilose under lens due to the projecting cystidia, pale orange (5A3) to greyish-orange [5B(3–6)], finely cracked with age; margin undifferentiated.

Microscopic structures

Hyphal system monomitic; generative hyphae with clamp connections, hyaline, thin-walled, moderately branched, frequently septate, loosely interwoven, 2–3 µm in diam. Cystidia abundant, subulate, projecting beyond hymenium, multi-rooted, hyaline, distinctly thick-walled, slightly amyloid, covered with dendroid branching hyphae, 70–100 × 10–16 µm. Basidia subclavate, hyaline, thin-walled, with 4 sterigmata and a basal clamp connection, 18–25 × 8–10 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores narrowly fusiform to vermicular, bi-apiculate, hyaline, thin-walled, smooth, negative in Melzer’s reagent, acyanophilous, (17–)20–29(–30) × (2–)2.2–3(–3.2) µm, L = 23.9 µm, W = 2.6 µm, Q = 9–9.5 (n = 60/2).

Additional specimens examined

CHINA. Guizhou Province, Libo County, Maolan Nature Reserve, on rotten culms of bamboo, 11 Jul 2017, He 4776 (BJFC 024293).

Remarks

Tubulicium bambusicola is distinguished by its large vermicular basidiospores and growing on bamboo. Three taxa, T. raphidisporum (Boidin & Gilles) Oberw., Kisim.-Hor. & L.D. Gómez, T. vermiferum (Bourdot) Oberw. and T. vermiferum var. hexasterigmatum J. Kaur & Dhingra are similar to T. bambusicola by sharing long vermicular basidiospores but differ in the width of basidiospores (≥ 3.5 µm) and growing on woody plant. Tubulicium junci-acuti Boidin & Gaignon on Juncus acutus differs from T. bambusicola by having shorter and wider basidiospores (15–20 × 3–4.25 µm, Boidin and Gaignon 1992).

Figure 6. 

Tubulicium bambusicola (holotype, He 4058). a basidiomata b, d basidiospores c, e cystidia f basidia and a basidiole g subicular hyphae. Scale bars: 1 cm (a), 10 µm (b–g). b, c Taken in phloxine.

Discussion

Nine genera in the Trechisporales were included in the present analyses and the results mostly agree with previous studies (Larsson 2007; Birkebak et al. 2013; Telleria et al. 2013a). Most of the sampled genera were retrieved as monophyletic except Scytinopogon, which was nested within the Trechispora lineage (Fig. 2). A Dextrinocystis species was sequenced for the first time and its position in Hydnodontaceae was confirmed. As indicated by the morphology (Burdsall and Nakasone 1983; Gilbertson and Blackwell 1988; Moreno and Esteve-Raventós 2007; Nakasone 2013), the genus is closely related to Tubulicium. However, Tubulicium is morphologically heterogenous, with different basidiospores (Moreno and Esteve-Raventós 2007; Hjortstam and Ryvarden 2008) and only species with fusiform to vermicular basidiospores were sequenced. Moreover, Dextrinocystis is well distinguished from Tubulicium by its distinctly dextrinoid cystida and cylindrical basidiospores (Gilbertson and Blackwell 1988; Nakasone 2013). Thus, at present, the authors prefer to retain them as separate genera until more species are sequenced.

Subulicystidium is a well-circumscribed genus characterised by the unique cystidia encrusted with rectangular crystals and fusiform to vermicular basidiospores (Bernicchia and Gorjón 2010; Ordynets et al. 2018). Although all the sampled species formed a strongly supported lineage in the tree (Fig. 2), the species S. oberwinkleri Ordynets, Riebesehl & K.H.Larss. was not congeneric with other species and excluded from our analyses. Ordynets et al. (2018) showed that S. oberwinkleri formed a distinct basal lineage in the ITS-nrLSU tree. The phylogenetic position of the species in Trechisporales needs to be further studied.

Key to accepted genera in Trechisporales

1 Basidiomata clavarioid Scytinopogon
Basidiomata resupinate or stipitate hydnoid 2
2 Hymenophore poroid 3
Hymenophore non-poroid 4
3 Basidiospores smooth Porpomyces
Basidiospores ornamented Trechispora p.p.
4 Basidiomata brown Luellia
Basidiomata light coloured 5
5 Cystidia present, large and distinct 6
Cystidia absent or indistinct 8
6 Cystidia distinctly dextrinoid in Melzer’s reagent Dextrinocystis
Cystidia negative or amyloid in Melzer’s reagent 7
7 Cystidia regularly encrusted with rectangular crystals Subulicystidium
Cystidia usually covered with dendroid hyphae Tubulicium
8 Generative hyphae with ampullate septa Trechispora p.p.
Generative hyphae without ampullate septa 9
9 Subhymenial hyphae isodiametric Brevicellicium
Subhymenial hyphae not isodiametric 10
10 Hyphal system dimitic; basidia with 4 sterigmata Fibrodontia
Hyphal system monomitic; basidia with 4–8 sterigmata Sistotremastrum

Acknowledgements

The authors thank Dr. Karen Nakasone (Center for Forest Mycology Research, Northern Research Station, U.S. Forest Service, Madison, USA) for literature loan and critical suggestions on the manuscript. This study was supported by the Fundamental Research Funds for the Central Universities (No. 2016ZCQ04) and the National Natural Science Foundation of China (Nos. 31750001 & 31670013).

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