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Research Article
Elaphroporia ailaoshanensis gen. et sp. nov. in Polyporales (Basidiomycota)
expand article infoZi-Qiang Wu, Tai-Min Xu, Shan Shen, Xiang-Fu Liu, Kai-Yue Luo, Chang-Lin Zhao
‡ Southwest Forestry University, Kunming, China
Open Access

Abstract

A new poroid wood-inhabiting fungal genus, Elaphroporia, typified by E. ailaoshanensis sp. nov., is proposed based on a combination of morphological features and molecular evidence. The genus is characterised by an annual growth habit, resupinate basidiocarps, becoming rigid and light-weight up on drying, a monomitic hyphal system with thick-walled generative hyphae bearing both clamp connections and simple septa, slightly amyloid, CB+ and ellipsoid, hyaline, thin-walled, smooth and IKI–, CB– basidiospores. Sequences of ITS and LSU nrRNA gene regions of the studied samples were generated, and phylogenetic analyses were performed with maximum likelihood, maximum parsimony and bayesian inference methods. The phylogenetic analysis based on molecular data of ITS+nLSU sequences showed that Elaphroporia belonged to the residual polyporoid clade and was closely related to Junghuhnia crustacea. Further investigation was obtained for more representative taxa in the Meruliaceae based on ITS+nLSU sequences, in which the result demonstrated that the genus Elaphroporia formed a monophyletic lineage with a strong support (100 % BS, 100 % BP, 1.00 BPP) and then grouped with Flaviporus and Steccherinum.

Keywords

Meruliaceae, phylogeny, polypore, taxonomy, wood-inhabiting fungi

Introduction

The Polyporales is a large group of Agaricomycetes and includes more than 1800 taxa at species level belonging to 216 genera and 13 families (Kirk et al. 2008). Species in Polyporales are the key players amongst the wood-rotting fungi because of their importance in the carbon cycle (Floudas et al. 2012) and the pathogenic and potential application in biomedical engineering and biodegradation (Dai et al. 2009, Levin et al. 2016).

Molecular systematics has played a powerful role in inferring phylogenies within fungal groups since the early 1990s (White et al. 1990, Hibbett et al. 2007, Larsson 2007, Miettinen et al. 2011, Binder et al. 2013, Dai et al. 2015, Choi and Kim 2017). Recently, molecular studies involving Meruliaceae P. Karst. have been carried out (Binder et al. 2005, 2013, Miettinen and Larsson 2011, Miettinen and Rajchenberg 2012, Hibbett et al. 2016, Miettinen et al. 2016).

Larsson (2007) introduced a new division for part of the Polyporales, effectively renaming the phlebioid and residual polyporoid clades as the Meruliaceae, Phanerochaetaceae Jülich, and Byssomerulius Parmasto families. A phylogenetic study of Meruliaceae employing multi-genes suggested that 1) this family included species with both poroid and hydnoid hymenophore configurations, and 2) the genera of Flabellophora G. Cunn., Flaviporus Murrill, Junghuhnia Corda, Steccherinum Gray and Xanthoporus Audet belong to this family (Miettinen et al. 2011). Moreover, further study employing a six-gene (5.8S, nrLSU, nrSSU, rpb1, rpb2, tef1) dataset has constructed a phylogenetic and phylogenomic overview of the Polyporales, which showed that the species of Meruliaceae fall into the residual polyporoid clade (Binder et al. 2013).

Wood-rotting fungi is a cosmopolitan group and it has a rich diversity on the basis of growing on boreal, temperate, subtropical, and tropical vegetations (Gilbertson and Ryvarden 1987, Núñez and Ryvarden 2001, Dai 2012, Ryvarden and Melo 2014, Dai et al. 2015). During investigations on wood-inhabiting fungi in southern China, an additional taxon was found which could not be assigned to any described genus. It produces annual, resupinate basidiocarps, a monomitic hyphal system with generative hyphae bearing both simple septa and clamp connections, slightly amyloid, CB+ and ellipsoid, hyaline, thin-walled, smooth basidiospores. These characters make it distinguishable from all known poroid and hydnoid wood-inhabiting fungal genera (Gilbertson and Ryvarden 1987, Núñez and Ryvarden 2001, Bernicchia and Gorjón 2010, Ryvarden and Melo 2014). In this study, the authors expand samplings from previous studies to examine taxonomy and phylogeny of this new genus within the Polyporales, based on the internal transcribed spacer (ITS) regions and the large subunit nuclear ribosomal RNA gene (nLSU) sequences.

Materials and methods

Morphological studies. The specimens studied are deposited at the herbarium of Southwest Forestry University (SWFC). Macro-morphological descriptions are based on field notes. Special colour terms follow Petersen (1996). Micro-morphological data were obtained from the dried specimens and observed under a light microscope following Dai (2010). The following abbreviations were used: KOH = 5% potassium hydroxide, CB = Cotton Blue, CB– = acyanophilous, IKI = Melzer’s reagent, IKI– = both inamyloid and indextrinoid, IKI+ = amyloid, L = mean spore length (arithmetic average of all spores), W = mean spore width (arithmetic average of all spores), Q = variation in the L/W ratios between the specimens studied, n (a/b) = number of spores (a) measured from given number (b) of specimens.

DNA extraction and sequencing. CTAB rapid plant genome extraction kit-DN14 (Aidlab Biotechnologies Co., Ltd, Beijing) was used to obtain genomic DNA from dried specimens, according to the manufacturer’s instructions with the modification that a small piece of dried fungal specimen (about 30 mg) was ground to powder with liquid nitrogen. The powder was transferred to a 1.5 ml centrifuge tube, suspended in 0.4 ml of lysis buffer and incubated in a 65 °C water bath for 60 min. After that, 0.4 ml phenol-chloroform (24:1) was added to each tube and the suspension was shaken vigorously. After centrifugation at 13 000 rpm for 5 min, 0.3 ml supernatant was transferred to a new tube and mixed with 0.45 ml binding buffer. The mixture was then transferred to an adsorbing column (AC) for centrifugation at 13 000 rpm for 0.5 min. Then, 0.5 ml inhibitor removal fluid was added in AC for a centrifugation at 12 000 rpm for 0.5 min. After washing twice with 0.5 ml washing buffer, the AC was transferred to a clean centrifuge tube, and 100 ml elution buffer was added to the middle of the adsorbed film to elute the genome DNA. The ITS region was amplified with primer pairs ITS5 and ITS4 (White et al. 1990). The nuclear LSU region was amplified with primer pairs LR0R and LR7 (https://sites.duke.edu/vilgalyslab/rdna_primers_for_fungi/). The PCR procedure for ITS was as follows: initial denaturation at 95 °C for 3 min, followed by 35 cycles at 94 °C for 40 s, 58 °C for 45 s and 72 °C for 1 min, and a final extension of 72 °C for 10 min. The PCR procedure for nLSU was as follows: initial denaturation at 94 °C for 1 min, followed by 35 cycles at 94 °C for 30 s, 48 °C for 1 min and 72 °C for 1.5 min, and a final extension of 72 °C for 10 min. The PCR products were purified and directly sequenced at Kunming Tsingke Biological Technology Limited Company. All newly generated sequences were deposited at GenBank (Table 1).

A list of species, specimens and GenBank accession number of sequences used in this study.

Species name Sample no. GenBank accession no. References
ITS nLSU
Abortiporus biennis TFRI 274 EU232187 EU232235 Larsson (2007)
Antrodia albida CBS 308.82 DQ491414 AY515348 Kim et al. (2007)
Antrodia heteromorpha CBS 200.91 DQ491415 AY515350 Kim et al. (2007)
Antrodiella americana Gothenburg 3161 JN710509 JN710509 Miettinen et al. (2011)
Antrodiella pallasii Renvall 89a AF126896 Binder et al. (2013)
Antrodiella semisupina FCUG 960 EU232182 EU232266 Binder et al. (2005)
Antrodiella sp. X 418 JN710523 JN710523 Miettinen et al. (2011)
Atraporiella neotropica Ryvarden 44447 HQ659221 HQ659221 Miettinen and Rajchenberg (2012)
Ceriporia viridans Dai 7759 KC182777 Jia et al. (2014)
Ceriporiopsis balaenae H7002389 FJ496669 FJ496717 Tomšovský et al. (2010)
Ceriporiopsis consobrina Rivoire 977 FJ496667 FJ496716 Tomšovský et al. (2010)
Ceriporiopsis gilvescens BRNM 667882 FJ496685 FJ496719 Tomšovský et al. (2010)
Ceriporiopsis gilvescens BRNM 710166 FJ496684 FJ496720 Tomšovský et al. (2010)
Ceriporiopsis gilvescens Yuan 2752 KF845946 KF845953 Zhao and Cui (2014)
Ceriporiopsis guidella HUBO 7659 FJ496687 FJ496722 Tomšovský et al. (2010)
Cinereomyces lindbladii FBCC 177 HQ659223 HQ659223 Miettinen and Rajchenberg (2012)
Climacocystis borealis KH 13318 JQ031126 JQ031126 Binder et al. (2013)
Coriolopsis caperata LE(BIN)-0677 AB158316 AB158316 Tomšovský et al. (2010)
Dacryobolus karstenii KHL 11162 EU118624 EU118624 Binder et al. (2005)
Daedalea quercina DSM 4953 DQ491425 DQ491425 Kim et al. (2007)
Diplomitoporus flavescens X 84 FN907908 Miettinen et al. (2011)
Earliella scabrosa PR1209 JN165009 JN164793 Justo and Hibbett (2011)
Etheirodon fimbriatum Larsson 11905 JN710530 JN710530 Miettinen et al. (2011)
Flabellophora sp.1 X 1357 JN710533 JN710533 Miettinen et al. (2011)
Flabellophora sp.2 X 340 JN710534 JN710534 Miettinen et al. (2011)
Flabellophora sp.3 X 1277 JN710535 JN710535 Miettinen et al. (2011)
Flabellophora sp.4 X 439 JN710536 JN710536 Miettinen et al. (2011)
Flaviporus brownii X 1216 JN710537 JN710537 Miettinen et al. (2011)
Flaviporus liebmannii X 251 JN710541 JN710541 Miettinen et al. (2011)
Flaviporus liebmannii X 249 JN710539 JN710539 Miettinen et al. (2011)
Flaviporus liebmannii X 666 JN710540 JN710540 Miettinen et al. (2011)
Fomitopsis pinicola CBS 221.39 DQ491405 DQ491405 Kim et al. (2007)
Fomitopsis rosea ATCC 76767 DQ491410 DQ491410 Kim et al. (2007)
Fragiliporia fragilis Dai 13080 KJ734260 KJ734264 Zhao et al. (2015)
Fragiliporia fragilis Dai 13559 KJ734261 KJ734265 Zhao et al. (2015)
Fragiliporia fragilis Dai 13561 KJ734262 KJ734266 Zhao et al. (2015)
Frantisekia mentschulensis BRNM 710170 FJ496728 Tomšovský et al. (2010)
Frantisekia mentschulensis 1377 JN710544 JN710544 Miettinen et al. (2011)
Ganoderma lingzhi Wu 1006-38 JQ781858 Zhao et al. (2015)
Gelatoporia subvermispora BRNU 592909 FJ496694 FJ496706 Tomšovský et al. (2010)
Gloeoporus dichrous KHL 11173 EU118627 EU118627 Binder et al. (2005)
Grammothelopsis subtropica Cui 9035 JQ845094 JQ845097 Zhao et al. (2015)
Heterobasidion annosum PFC 5252 KC492906 KC492906 Binder et al. (2013)
Hornodermoporus martius MUCL 41677 FJ411092 FJ393859 Zhao et al. (2015)
Hypochnicium bombycinum MA 15305 FN552537 Binder et al. (2013)
Hypochnicium lyndoniae NL 041031 JX124704 JX124704 Binder et al. (2005)
Junghuhnia crustacea X 1127 JN710554 JN710554 Miettinen et al. (2011)
Junghuhnia crustacea X 262 JN710553 JN710553 Miettinen et al. (2011)
Junghuhnia micropora Spirin 2652 JN710559 JN710559 Miettinen et al. (2011)
Junghuhnia nitida KHL 11903 EU118638 EU118638 Binder et al. (2005)
Loweomyces fractipes X 1149 JN710570 JN710570 Miettinen et al. (2011)
Loweomyces fractipes X 1253 JN710569 JN710569 Miettinen et al. (2011)
Loweomyces fractipes X 1250 JN710568 JN710568 Miettinen et al. (2011)
Mycoacia fuscoatra KHL 13275 JN649352 JN649352 Tomšovský et al. (2010)
Mycoacia nothofagi KHL 13750 GU480000 GU480000 Tomšovský et al. (2010)
Nigroporus vinosus X 839 N710576 N710576 Miettinen et al. (2011)
Nigroporus vinosus 8182 JN710728 JN710728 Miettinen et al. (2011)
Obba rivulosa KCTC 6892 FJ496693 FJ496710 Miettinen and Rajchenberg (2012)
Obba valdiviana FF 503 HQ659235 HQ659235 Miettinen and Rajchenberg (2012)
Panus conchatus X 1234 JN710579 JN710579 Miettinen et al. (2011)
Panus strigellus INPA 243940 JQ955725 JQ955732 Binder et al. (2013)
Perenniporia medulla-panis MUCL 49581 FJ411088 FJ393876 Robledo et al. (2009)
Perenniporiella neofulva MUCL 45091 FJ411080 FJ393852 Robledo et al. (2009)
Phlebia unica KHL 11786 EU118657 EU118657 Binder et al. (2013)
Phlebia radiata UBCF 19726 HQ604797 HQ604797 Binder et al. (2013)
Physisporinus sanguinolentus BRNM 699576 FJ496671 FJ496725 Tomšovský et al. (2010)
Physisporinus vitreus 3163 JN710580 JN710580 Miettinen et al. (2011)
Piloporia sajanensis Mannine 2733a HQ659239 HQ659239 Miettinen and Rajchenberg (2012)
Podoscypha venustula CBS 65684 JN649367 JN649367 Binder et al. (2013)
Polyporus tuberaster CulTENN 8976 AF516598 AJ488116 Binder et al. (2005)
Postia guttulata KHL 11739 EU11865 EU11865 Kim et al. (2007)
Pseudolagarobasidium acaciicola CBS 115543 DQ517883 Miettinen and Rajchenberg (2012)
Pseudolagarobasidium acaciicola CBS 115544 DQ517882 Miettinen and Rajchenberg (2012)
Pseudolagarobasidium belizense CFMR 04-31 JQ070173 Miettinen and Rajchenberg (2012)
Skeletocutis amorpha Miettinen 11038 FN907913 FN907913 Tomšovský et al. (2010)
Skeletocutis portcrosensis LY 3493 FJ496689 FJ496689 Tomšovský et al. (2010)
Skeletocutis jelicii H 6002113 FJ496690 FJ496727 Tomšovský et al. (2010)
Skeletocutis novae-zelandiae Ryvarden 38641 JN710582 JN710582 Miettinen et al. (2011)
Spongipellis spumeus PRM 891931 HQ728287 HQ729021 Tomšovský et al. (2010)
Spongipellis spumeus BRNM 712630 HQ728288 HQ728288 Tomšovský et al. (2010)
Spongipellis spumeus BRNM 734877 HQ728283 HQ728283 Tomšovský et al. (2010)
Steccherinum fimbriatum KHL 11905 EU118668 EU118668 Tomšovský et al. (2010)
Steccherinum ochraceum Ryberg s.n. EU118669 EU118670 Larsson (2007)
Steccherinum ochraceum KHL 11902 JQ031130 JQ031130 Miettinen et al. (2011)
Stereum hirsutum NBRC 6520 AB733150 AB733325 Binder et al. (2013)
Truncospora ochroleuca MUCL 39726 FJ411098 FJ393865 Robledo et al. (2009)
Tyromyces chioneus Cui 10225 KF698745 KF698756 Zhao et al. (2015)
Xanthoporus syringae X 339 JN710606 JN710606 Miettinen et al. (2011)
Xanthoporus syringae Cui 2177 DQ789395 Miettinen et al. (2011)
Xanthoporus syringae Gothenburg 1488 JN710607 JN710607 Miettinen et al. (2011)
Elaphroporia ailaoshanensis CLZhao 595 MG231568 MG748854 Present study
Elaphroporia ailaoshanensis CLZhao 596 MG231572 MG748855 Present study
Elaphroporia ailaoshanensis CLZhao 597 MG231847 MG748856 Present study
Elaphroporia ailaoshanensis CLZhao 598 MG231823 MG748857 Present study

Phylogenetic analysis. Sequencher 4.6 (GeneCodes, Ann Arbor, MI, USA) was used to edit the DNA sequence. Sequences were aligned in MAFFT 6 (Katoh and Toh 2008, http://mafft.cbrc.jp/alignment/server/) using the “G-INS-I” strategy and manually adjusted in BioEdit (Hall 1999). The sequence alignment was deposited in TreeBase (submission ID 21778). Sequences of Heterobasidion annosum (Fr.) Bref. and Stereum hirsutum (Willd.) Pers. obtained from GenBank were used as outgroups to root trees following Binder et al. (2013) in Figure 1 and Xanthoporus syringae (Parmasto) Audet. obtained from GenBank was used as an outgroup to root trees following Miettinen et al. (2011) in the ITS+nLSU analyses (Fig. 2).

Figure 1. 

Maximum parsimony strict consensus tree illustrating the phylogeny of Elaphroporia ailaoshanensis and related species in Polyporales based on ITS+nLSU sequences. Branches are labelled with parsimony bootstrap values (before slash) higher than 50 % and Bayesian posterior probabilities (after slash) equal to and more than 0.95. Clade names follow Binder et al. (2013).

Figure 2. 

Maximum parsimony strict consensus tree illustrating the phylogeny of Elaphroporia ailaoshanensis and related species in the residual polyporoid clade based on ITS+nLSU sequences. Branches are labelled with parsimony bootstrap values (before slash) higher than 50% and Bayesian posterior probabilities (after slash) equal to and more than 0.95. Clade names follow Miettinen et al. (2011).

Maximum parsimony analysis was applied to the ITS+nLSU dataset sequences. Approaches to phylogenetic analysis followed Li and Cui (2013) and the tree construction procedure was performed in PAUP* version 4.0b10 (Swofford 2002). All characters were equally weighted and gaps were treated as missing data. Trees were inferred using the heuristic search option with TBR branch swapping and 1000 random sequence additions. Max-trees were set to 5000, branches of zero length were collapsed and all parsimonious trees were saved. Clade robustness was assessed using a bootstrap (BT) analysis with 1,000 replicates (Felsenstein 1985). Descriptive tree statistics tree length (TL), consistency index (CI), retention index (RI), rescaled consistency index (RC) and homoplasy index (HI) were calculated for each Maximum Parsimonious Tree (MPT) generated. Sequences were also analysed using Maximum Likelihood (ML) with RAxML-HPC2 through the Cipres Science Gateway (www.phylo.org; Miller et al. 2009). Branch support for ML analysis was determined by 1000 bootstrap replicates.

MrModeltest 2.3 (Posada and Crandall 1998, Nylander 2004) was used to determine the best-fit evolution model for each data set for Bayesian Inference (BI). Bayesian Inference was calculated with MrBayes 3.1.2 with a general time reversible (GTR) model of DNA substitution and a gamma distribution rate variation across sites (Ronquist and Huelsenbeck 2003). Four Markov chains were run for 2 runs from random starting trees for 5 million generations (Fig. 1), for 3 million generations (Fig. 2) and trees were sampled every 100 generations. The first one-fourth generations were discarded as burn-in. A majority rule consensus tree of all remaining trees was calculated. Branches that received bootstrap support for maximum likelihood (BS), maximum parsimony (BP) and Bayesian posterior probabilities (BPP) greater than or equal to 75 % (BP) and 0.95 (BPP) respectively, were considered as significantly supported.

Phylogeny results

The ITS+nLSU dataset (Fig. 1) included sequences from 60 fungal specimens representing 52 taxa. The dataset had an aligned length of 2143 characters, of which 1251 characters were constant, 206 parsimony-uninformative and 686 parsimony-informative. MP analysis yielded 6 equally parsimonious trees (TL = 4744, CI = 0.322, HI = 0.678, RI = 0.578, RC = 0.186). The best-fit model for ITS+nLSU alignment estimated and applied in the BI was GTR+I+G, lset nst = 6, rates = invgamma; prset statefreqpr = dirichlet (1,1,1,1). BI resulted in a similar topology with an average standard deviation of split frequencies = 0.001755.

The phylogenetic tree (Fig. 1), inferred from ITS+nLSU sequences, demonstrated seven major clades for 60 sampled species of the Polyporales. The new genus Elaphroporia fell into the Meruliaceae within the residual polyporoid clade. It was closely related to Junghuhnia crustacea (Jungh.) Ryvarden with a good support (95% BS, 89% BP, 0.97 BPP).

The ITS+nLSU (Fig. 2) dataset included sequences from 48 fungal specimens representing 31 taxa. The dataset had an aligned length of 2163 characters, of which 1429 characters were constant, 169 parsimony-uninformative and 565 parsimony-informative. MP analysis yielded 8 equally parsimonious trees (TL = 2806, CI = 0.423, HI = 0.576, RI = 0.673, RC = 0.285). The best-fit model for ITS+nLSU alignment estimated and applied in the BI was GTR+I+G, lset nst = 6, rates = invgamma; prset statefreqpr = dirichlet (1,1,1,1). BI resulted in a similar topology with an average standard deviation of split frequencies equal to 0.005758.

A further phylogeny (Fig. 2) inferred from the combined ITS+nLSU sequences was obtained for 48 fungal specimens representing 31 taxa within the residual polyporoid clade and demonstrated that the new genus formed a monophyletic entity with a high 100 % BS, 100 % BP and 1.00 BPP and sisters to Junghuhnia crustacea and then grouped with Flaviporus and Steccherinum.

Taxonomy

Elaphroporia Z.Q. Wu & C.L. Zhao, gen. nov.

MycoBank No: 823915

Diagnosis

Differs from other genera in Polyporales by resupinate basidiocarps becoming rigid and light-weight upon drying, a monomitic hyphal system, thick-walled generative hyphae bearing both clamp connections and simple septa and hyaline, thin-walled, smooth, IKI–, CB– basidiospores.

Type species

Elaphroporia ailaoshanensis Z.Q. Wu & C.L. Zhao.

Etymology

Elaphroporia (Lat.): referring to the basidiocarps light-weight upon drying.

Basidiocarps annual, resupinate, becoming rigid and light-weight up on drying. Pore surface cream to pale yellow when fresh, turning to yellow upon drying. Hyphal system monomitic; generative hyphae thick-walled bearing both clamp connections and simple septa, slightly amyloid, CB+. Basidiospores ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–.

Elaphroporia ailaoshanensis Z.Q. Wu & C.L. Zhao, sp. nov.

MycoBank No: 823916
Figs 3, 4

Diagnosis

This species is distinguished by the cream to yellow pore surface upon drying; pores angular, 7–9 per mm. Hyphal system monomitic; generative hyphae thick-walled bearing both clamp connections and simple septa, slightly amyloid, CB+. Basidiospores ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, 1.9–2.5 × 1.5–2 µm.

Figure 3. 

Basidiomata of Elaphroporia ailaoshanensis (holotype). Scale bars: 1 cm (A); 1 mm (B).

Figure 4. 

Microscopic structures of Elaphroporia ailaoshanensis (drawn from the holotype). A Basidiospores B Basidia and basidioles C Hyphae from trama D Hyphae from subiculum.

Holotype

CHINA. Yunnan Province: Jingdong county, Ailaoshan Nature Reserve, 2 October 2016, on the angiosperm trunk, CLZhao 595 (Holotype in SWFC).

Etymology

Ailaoshanensis (Lat.): referring to the locality (Ailaoshan) of the type specimens.

Basidiocarps

Annual, resupinate, easy to separate from substrate, soft corky when fresh, without odour or taste when fresh, becoming rigid and light-weight up on drying, up to 5 cm long, 3.5 cm wide, 4 mm thick at centre. Pore surface cream to pale yellow when fresh, turning to yellow upon drying; pores angular, 7–9 per mm; dissepiments thin, entire. Sterile margin narrow, cream, up to 1 mm wide. Subiculum thin, cream, corky, up to 0.2 mm thick. Tubes concolorous with pore surface, hard corky, up to 3.8 mm long.

Hyphal structure

Hyphal system monomitic; generative hyphae thick-walled, slightly amyloid, CB+; tissues unchanged in KOH.

Subiculum

Generative hyphae hyaline, thick-walled bearing both clamp connections and simple septa, simple septa more frequent than clamps, occasionally branched, interwoven, 3.5–5.5 µm in diam.

Tubes

Generative hyphae hyaline, thick-walled bearing simple septa only, occasionally branched, 3–5 µm in diameter. Cystidia and cystidioles absent; basidia clavate, with four sterigmata and a basal clamp connection, 10.5–14.5 × 3.5–4.5 µm; basidioles dominant, in shape similar to basidia, but slightly smaller.

Spores

Basidiospores ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, (1.7–)1.9–2.5(–2.9) × (1.3–)1.5–2(–2.2) µm, L = 2.29 µm, W = 1.74 µm, Q = 1.33–1.81 (n = 120/4).

Additional specimens examined

(paratypes). CHINA. Yunnan Province: Jingdong county, Ailaoshan Nature Reserve, 2 October 2016, on the angiosperm trunk, CLZhao 596, CLZhao 597, CLZhao 598 (SWFC).

Discussion

In the present study, a new genus, Elaphroporia, is described based on phylogenetic analyses and morphological characters. The genus has unique morphological characters in Meruliaceae.

Previously, seven clades were found in the Polyporales: antrodia clade, core polyporoid clade, fragiliporia clade, gelatoporia clade, phlebioid clade, residual polyporoid clade and tyromyces clade (Binder et al. 2013, Zhao et al. 2015). According to these results based on the combined ITS+nLSU sequence data (Fig. 1), the new genus is nested into the residual polyporoid clade with strong support (100 % BS, 100 % BP, 1.00 BPP).

Miettinen et al. (2011) analysed a higher-level phylogenetic classification of the residual polyporoid clade morphological plasticity in a group of the polypores, and showed that the natural genera could mostly be characterised morphologically and poroid and hydnoid species belong to separate genera. The current phylogeny shows that the genus Elaphroporia falls into the residual polyporoid clade and belongs to the family Meruliaceae (Figs 1, 2). Furthermore, the new genus is closely related to Junghuhnia and then grouped with Flaviporus and Steccherinum based on ITS+LSU-nrRNA gene regions with a strong support (100 % BS, 100 % BP, 1.00 BPP; Fig. 1). However, morphologically Junghuhnia differs from Elaphroporia by a dimitic hyphal system and presence of cystidia (Núñez and Ryvarden 2001, Ryvarden and Melo 2014). Flaviporus is separated from Elaphroporia by the dark brown to bay pileus, a dimitic hyphal system and presence of the metuloid cystidia (Murrill 1905). Steccherinum differs in its odontioid to hydnoid hymenophore and cyanophilous basidiospores (Bernicchia and Gorjón 2010).

Morphologically, Elaphroporia resembles Ceriporia Donk and Phlebiporia Jia J. Chen, B.K. Cui & Y.C. Dai. Ceriporia is similar to Elaphroporia in an annual growth habit with poroid hymenophore, a monomitic hyphal structure and hyaline, thin-walled and smooth basidiospores. In addition, both genera cause a white rot. However, Ceriporia differs from Elaphroporia by the generative hyphae IKI–, CB– (Jia et al. 2014). Additionally, in molecular studies, Ceriporia fell into the phlebia clade (Miettinen and Larsson 2011, Miettinen and Rajchenberg 2012, Miettinen et al. 2011, Binder et al. 2013) which is also the same as in the authors’ study (Fig. 1). Phlebiporia is similar to Mellipora by having the poroid hymenophore and the generative hyphae bearing both simple septa and clamp connections, but it is separated from Elaphroporia by having dextrinoid generative hyphae, tissues becoming brownish in KOH and presence of thin-walled quasi-binding hyphae in the subiculum (Chen and Cui 2014).

Polypores are an extensively studied group of Basidiomycota (Gilbertson and Ryvarden 1987, Núñez and Ryvarden 2001, Dai 2012, Ryvarden and Melo 2014), but the Chinese polypore diversity is still not well known, especially in subtropics and tropics, from where many recently described taxa of polypores were discovered (Song et al. 2014, 2016, Zhou et al. 2015, 2016, Nie et al. 2017, Yuan et al. 2017). The new genus in the present study, Elaphroporia, is also from the subtropics. It is possible that new polypore taxa will be found after further investigations and molecular analyses.

Acknowledgments

We express our gratitude to Yong-He Li (Yunnan Academy of Biodiversity, Southwest Forestry University, P.R. China) for his support on molecular work. The research is supported by the National Natural Science Foundation of China (Project No. 31700023) and the Science Foundation of Southwest Forestry University (Project No. 111715) and the Science and Technology Talent Support Programme of Three Areas in Yunnan Province (Project No. 21700329).

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