Biodiversity Data Journal : Taxonomic Paper
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Taxonomic Paper
Arthrinium bambusicola (Fungi, Sordariomycetes), a new species from Schizostachyum brachycladum in northern Thailand
expand article infoXia Tang‡,§,|, Ishani D. Goonasekara§,|,, Ruvishika S. Jayawardena§,|, Hong Bo Jiang§,|,, Jun F. Li§,|,, Kevin D. Hyde§,|, Ji C. Kang
‡ Engineering and Research Center for Southwest Biopharmaceutical Resource of National Education Ministry of China, Guizhou University, Guiyang 550025, Guizhou, P.R. China, Guiyang, China
§ Centre of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai 57100, Thailand, Chiang Rai, Thailand
| School of science, Mae Fah Luang University, Chiang Rai 57100, Thailand, Chiang Rai, Thailand
¶ Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Science, Kunming 650201, Yunnan, P.R. China, Kunming, China
Open Access

Abstract

Background

Species of the fungal genus Arthrinium (Sordariomycetes, Amphisphaeriales, Apiosporaceae) are often found on bamboo in Asia. They are endophytes, saprobes and important plant pathogens. The genus Arthrinium currently contains 92 species and is widely distributed in North and South America, Europe, Africa, Asia and Oceania.

New information

In this study, a new species, Arthrinium bambusicola sp. nov., is described and illustrated. The new taxon is characterised by oval to broadly or irregularly round, medium brown, multi-guttulate to roughened, granular conidia, with finely pale slits in the outer edges. Arthrinium bambusicola can be distinguished from the closest related species A. gutiae by its conidial characteristics. Phylogenetic analyses of a four-locus dataset (ITS, LSU, TEF1, TUB2) confirm that A. bambusicola is a distinct new species.

Keywords

one new species, Bambusicolous fungi, multi-locus phylogeny, saprobic, Sordariomycetes, taxonomy

Introduction

The genus Arthrinium, with A. caricicola as type species, was established by Schmidt and Kunze (Kunze 1817). Species of Arthrinium are endophytes, saprobes and important plant pathogens of various hosts, particularly grasses and bamboo (Agut and Calvo 2004, Li et al. 2016, Dai et al. 2017, Wang et al. 2018, Jiang et al. 2019, Rashmi et al. 2019). The sexual morph is characterised by black, linear, fusiform ascostromata with a long, slit-like opening at the apex. The ascomata are globose to subglobose, with flattened bases and brown to blackish, with or without setae (Jiang et al. 2019, Pintos et al. 2019, Yang et al. 2019).

Species of Arthrinium produce both hyphomycetous and coelomycetous asexual morphs. The hyphomycetous morph is characterised by septate conidiophores, arising from basal cells or that are reduced to conidiogenous cells. Conidiogenous cells are holoblastic, monoblastic or polyblastic and are hyaline to pale brown, smooth or finely roughened, doliiform, ampulliform or subcylindrical and conidia are dark brown, brown to pale olivaceous and of various shapes (Hyde et al. 2016). The coelomycetous morph is immersed, black, globose to subglobose, septate, hyphoid conidiomata and hyaline to pale brown conidiophores arising from basal cells or that are reduced to conidiogenous cells. The conidiogenous cells are subhyaline to pale brown, smooth-walled or verrucose, holoblastic, monoblastic or polyblastic and cylindrical. The conidia are dark brown, smooth, globose to subglobose, with or without a germ slit or truncate scar at the base (Senanayake et al. 2015, Dai et al. 2017, Jiang et al. 2018, Yang et al. 2019). The presence of both hyphomycetous and coelomycetous asexual morphs has complicated the taxonomy of Arthrinium .

There are 92 species epithets for Arthrinium in Index Fungorum (2020). A total of 63 species have been introduced, based on the combination of morphological and molecular phylogenetic data (Wijayawardene et al. 2017, Jiang et al. 2018, Wang et al. 2018, Zhao et al. 2018, Jiang et al. 2019, Pintos et al. 2019, Yan et al. 2019, Yang et al. 2019). In this study, we propose a new species, based on morphological study and comparison with other species, in combination with phylogenetic analyses of a concatenated dataset of ITS, LSU, TEF1 and TUB2 sequences.

Materials and methods

Sample collection and isolation

Fresh samples of dead culms of Schizostachyum brachycladum (Poales, Poaceae and Bambusoideae) were collected at the campus of Mae Fah Luang University, Chiang Rai, Thailand on 7 May 2019. Single-spore isolation was performed as in Chomnunti et al. (2014). The holotype is deposited at the herbarium of Mae Fah Luang University, Chiang Rai, Thailand (MFLU) and the ex-type living culture is preserved at the Mae Fah Luang University Culture Collection (MFLUCC). Facesoffungi and Index Fungorum numbers for the new taxon were obtained (Jayasiri et al. 2015, Index Fungorum 2020).

Morphological examination

Conidiomata present on the surface of the host were observed using a stereomicroscope (Motic SMZ-171, Wetzlar, Germany). Sections of conidiomata were taken and mounted in water on a microscope slide to observe fungal characters. Photographs were taken using a Nikon ECLIPSE Ni-U compound microscope connected with a Nikon camera series DS-Ri2. Morphological structures (conidiophores, conidiogenous cells, conidia) were measured by Image Frame Work software v. 0.9.7. Adobe Photoshop CC 2019 was used for editing the photographic plate. Colonies were described, based on the colour charts of Rayner (1970).

DNA extraction, PCR amplification and sequencing

Genomic DNA was extracted from fresh mycelia obtained from living cultures that were grown on potato dextrose agar (PDA) for 15 days at room temperature, using the EZgene Fungal gDNA Kit (GD2416, Biomiga, San Diego, California, USA) following the manufacturer’s instructions. PCR amplification was done for the internal transcribed spacer region (ITS), the large subunit of the ribosomal RNA gene (LSU), translation elongation factor 1-alpha (TEF1) and beta-tubulin (TUB2). The following primers were used: ITS5 and ITS4 for ITS (White et al. 1990); LR0R and LR5 for LSU (Vilgalys and Hester 1990, Hopple 1994); EF1-728F and EF-2 for TEF1 (O’Donnell et al. 1998, Carbone and Kohn 1999).

PCR amplification was done in 50-μl volumes consisting of 2 μl of DNA template, 2 μl of each 10 μM forward and reverse primers, 25 μl of 2 ×Taq PCR Master Mix and 19 μl of deionised water. Cycling conditions were as follows: for ITS: initial denaturation at 94°C for 5 min, then 35 cycles of denaturation at 94°C for 45 s, annealing at 52°C for 50 s and extension at 72°C for 1 min; and final extension at 72°C for 10 min. For LSU: initial denaturation at 94°C for 5 min, then 35 cycles of denaturation at 94°C for 45 s, annealing at 52°C for 50 s and extension at 72°C for 1 min; and final extension at 72°C for 10 min. Lastly, for TEF1: initial denaturation at 94°C for 5 min; then 35 cycles of denaturation at 94°C for 1 min, annealing at 56°C for 1 min and extension at 72°C for 90 s; and final extension at 72°C for 10 min.

PCR products were checked in 1% agarose gels and sent to Sangon Biotech (Shanghai) Co. Ltd, China for sequencing, using the same primers.

Phylogenetic analyses

Raw sequence reads were combined using BioEdit v. 7.0.5.3 (Hall 1999) and subjected to BLASTn (https://blast.ncbi.nlm.nih.gov/Blast.cgi) to find closely-related taxa. To confirm the phylogenetic position of our taxon, sequences of four loci (ITS, LSU, TEF1 and TUB2) were downloaded from NCBI GenBank (Table 1). Note that no TUB2 sequence was generated for the new species, A. bambusicola. Notwithstanding, this locus was included in our phylogenetic analyses to increase phylogenetic resolution. Sequences of individual loci were aligned using MAFFT v. 7 using the 'auto' option (https://mafft.cbrc.jp/alignment/server/index.html) (Katoh et al. 2019) and, where necessary, improved in BioEdit v. 7.0.5.3 (Hall 1999). Multiple loci were combined by SequenceMatrix (Vaidya et al. 2011). The alignment was trimmed using trimAl v 1.2 with the 'gappyout' option (Capella-Gutiérrez et al. 2009). A phylogenetic tree was reconstructed from the concatenated ITS–LSU–TEF1–TUB2 dataset using Maximum Likelihood (ML), Maximum Parsimony (MP) and Bayesian Inference (BI) analyses.

Table 1.

Details of fungal taxa used in this study. Newly-generated sequences are indicated by ▲ after the species name; type materials are in bold.

Species Strain numbers Substrates Origin ITS LSU TUB2 TEF 1
Arthrinium aquaticum S-642 Submerged wood China MK828608 MK835806 - -
A. arundinis CBS 133509 Aspergillus flavus sclerotium buried in sandy field USA KF144886 KF144930 KF144976 KF145018
A. arundinis CBS 449.92 Bamboo Canada KF144887 KF144931 KF144977 KF145019
A. aureum CBS 244.83 - Japan AB220251 KF144935 KF144981 KF145023
A. balearicum CBS 145129 Undetermined Poaceae Spain MK014869 MK014836 MK017975 MK017946
A. bambusae LC7106 Leaves of bamboo China KY494718 KY494794 KY705186 KY806204
A. bambusae LC7124 Leaves of bamboo China KY494727 KY494803 KY705195 KY806206
A. bambusicola MFLUCC 20-0144 Culms of Schizostachyum brachycladum Thailand MW173030

MW173087

-

MW183262
A. camelliaesinensis LC5007 Camellia sinensis China KY494704 KY494780 KY705173 KY705103
A. camelliaesinensis LC8181 Brassica rapa China KY494761 KY494837 KY705229 KY705157
A. caricicola CBS 145127 Dead leaves of Carex ericetorum China MK014871 MK014838 MK017977 MK017948
A. chinense CFCC 53036 Fargesia qinlingensis China MK819291 - MK818547 MK818545
A. chinense CFCC 53037 Fargesia qinlingensis China MK819292 - MK818548 MK818546
A. chromolaenae MFLUCC 17-1505 Chromolaena odorata Thailand MT214342 MT214436 - MT235802
A. descalsii CBS 145130 Dead culms of Ampelodesmos mauritanicus Spain MK014870 MK014837 MK017976 MK017947
A. dichotomanthi LC4950 Dichotomanthes tristaniicarpa China KY494697 KY494773 KY705167 KY705096
A. dichotomanthi LC8175 Dichotomanthes tristaniicarpa China KY494755 KY494831 KY705223 KY705151
A. esporlense CBS 145136 Dead culms of Phyllostachys aurea Spain MK014878 MK014845 MK017983 MK017954
A. euphorbiae IMI 285638b Bambusa sp. Bangladesh AB220241 AB220335 AB220288 -
A. gaoyouense CFCC 52301 Living leaves and culms of Phragmites australis China MH197124 - MH236789 MH236793
A. gaoyouense CFCC 52302 Living leaves and culms of Phragmites australis China MH197125 - MH236790 MH236794
A. garethjonesii KUMCC 16-0202 Dead culms of bamboo China KY356086 KY356091 - -
A. guizhouense LC5318 Air in karst cave China KY494708 KY494784 KY705177 KY705107
A. guizhouense LC5322 Air in karst cave China KY494709 KY494785 KY705178 KY705108
A. gutiae CBS 135835 Gut of a grasshopper India KR011352 MH877577 KR011350 KR011351
A. hispanicum IMI 326877 Beach sand Spain AB220242 AB220336 AB220289 -
A. hydei CBS 114990 Culms of Bambusa tuldoides China KF144890 KF144936 KF144982 KF145024
A. hydei KUMCC 16-0204 Dead culms of bamboo China KY356087 KY356092 - -
A. hyphopodii MFLUCC 15-0003 Culms of Bambusa tuldoides China KR069110 - - -
A. hyphopodii KUMCC 16-0201 Culms of bamboo China KY356088 KY356093 - -
A. hysterinum CBS 145133 Phyllostachys aurea Spain MK014875 MK014842 MK017981 MK017952
A. hysterinum ICPM6889 Bamboo New Zealand MK014874 MK014841 MK017980 MK017951
A. ibericum CBS 145137 Dead culms of Arundo donax Portugal MK014879 MK014846 MK017984 MK017955
A. italicum CBS 145138 Dead culms of Arundo donax Italy MK014880 MK014847 MK017985 MK017956
A. italicum CBS 145139 Dead culms of Phragmites australis Spain MK014881 MK014848 MK017986 -
A. japonicum IFO30500 - Japan AB220262 AB220356 AB220309
A. japonicum IFO 31098 Leaves of Carex despalata Japan AB220264 AB220358 AB220311 -
A. jatrophae AMH-9557 Jatropha podagrica India JQ246355 - - -
A. jatrophae AMH-9556 Jatropha podagrica India HE981191 - - -
A. jiangxiense LC4494 Phyllostachys sp. China KY494690 KY494766 KY705160 KY705089
A. jiangxiense LC4577 Maesa sp. China KY494693 KY494769 KY705163 KY705092
A. kogelbergense CBS 113332 Dead culms of Cannomois virgata South Africa KF144891 KF144937 KF144983 KF145025
A. kogelbergense CBS 113333 Dead culms of Restionaceae South Africa KF144892 KF144938 KF144984 KF145026
A. locuta-pollinis LC11688 Bee bread China MF939596 - MF939623 MF939618
A. locuta-pollinis LC11683 Hive-stored pollen of Brassica campestris China MF939595 - MF939622 MF939616
A. longistromum MFLUCC 11-0479 Dead culms of bamboo Thailand KU940142 KU863130 - -
A. longistromum MFLUCC 11-0481 Dead culms of bamboo Thailand KU940141 KU863129 - -
A. malaysianum CBS 102053 Macaranga hullettii stems colonised by ants Malaysia KF144896 KF144942 KF144988 KF145030
A. marii CBS 497.90 Beach sands Spain AB220252 KF144947 KF144993 KF145035
A. mediterranei IMI 326875 Air Spain AB220243 AB220337 AB220290 -
A. minus AP25418 Leaves of Carex sp. China MK014872 MK014839 MK017978 MK017949
A. minus CBS 145131 Dead leaves of Carex sp. Germany MK014872 MK014839 MK017978 MK017949
A. mytilomorphum DAOM 214595 Dead blades of Andropogon sp. India KY494685 - - -
A. neogarethjonesii DQD 2019a Bamboo China MK070897 MK070898 - -
A. neosubglobosa JHB006 Dead culms of bamboo China KY356089 KY356094 - -
A. neosubglobosa KUMCC 16-0203 Bamboo China KY356090 KY356095 - -
A. obovatum LC4940 Lithocarpus sp. China KY494696 KY494772 KY705166 KY705095
A. obovatum LC8177 Lithocarpus sp. China KY494757 KY494833 KY705225 KY705153
A. ovatum CBS 115042 Arundinaria hindsii China KF144903 KF144950 KF144995 KF145037
A. paraphaeospermum MFLUCC 13-0644 Dead culms of bamboo Thailand KX822128 KX822124 - -
A. phaeospermum CBS 114317 Leaves of Hordeum vulgare Iran KF144906 KF144953 KF144998 KF145040
A. phaeospermum CBS 114318 Leaves of Hordeum vulgare Iran KF144907 KF144954 KF144999 KF145041
A. phragmitis CPC 18900 Culms of Phragmites australis Italy KF144909 KF144956 KF145001 KF145043
A. phyllostachium MFLUCC 18-1101 Dead culms of Phyllostachys heteroclada China MK351842 MH368077 MK291949 MK340918
A. piptatheri CBS 145149 Dead culms of Piptatherum miliaceum Spain MK014893 MK014860 - MK017969
A. pseudoparenchymaticum LC7234 Leaves of bamboo China KY494743 KY494819 KY705211 KY705139
A. pseudoparenchymaticum LC8173 Leaves of bamboo China KY494753 KY494829 KY705221 KY705149
A. pseudosinense CPC 21546 Leaves of bamboo Netherlands KF144910 KF144957 - KF145044
A. pseudospegazzinii CBS 102052 Macaranga hullettii stem colonised by ants Malaysia KF144911 KF144958 KF145002 KF145045
A. pterospermum CBS 123185 Leaves lesion of Machaerina sinclairii New Zealand KF144912 KF144959 KF145003 -
A. pterospermum CPC 20193 Leaves of Lepidosperma gladiatum Australia KF144913 KF144960 KF145004 KF145046
A. puccinioides CBS 549.86 Leaves of Lepidosperma gladiatum Germany AB220253 AB220347 AB220300 -
A. qinlingense CFCC 52303 Dead culms of Fargesia qinlingensis China MH197120 - MH236791 MH236795
A. qinlingense CFCC 52304 Dead culms of Fargesia qinlingensis China MH197121 - MH236792 MH236796
A. rasikravindrae LC8179 Brassica rapa China KY494759 KY494835 KY705227 KY705155
A. rasikravindrae NFCCI 2144 Soil Norway JF326454 - - -
A. sacchari CBS 372.67 Air - KF144918 KF144964 KF145007 KF145049
A. sacchari CBS 664.74 Soil under Calluna vulgaris Netherlands KF144919 KF144965 KF145008 KF145050
A. saccharicola CBS 191.73 Air Netherlands KF144920 KF144966 KF145009 KF145051
A. saccharicola CBS 831.71 - Netherlands KF144922 KF144969 KF145012 KF145054
A. serenense IMI 326869 Food, pharmaceutical excipients, atmosphere and home dust Spain AB220250 AB220344 AB220297 -
A. setostromum KUMCC 19-0217 Dead branches of bamboo China MN528012 MN528011 - MN527357
A. sporophleum CBS 145154 Dead leaves of Juncus sp. Spain MK014898 MK014865 MK018001 MK017973
A. subglobosum MFLUCC 11-0397 Dead culms of bamboo Thailand KR069112 KR069113 - -
A. subroseum LC7291 Leaves of bamboo China KY494751 KY494827 KY705219 KY705147
A. subroseum LC7292 Leaves of bamboo China KY494752 KY494828 KY705220 KY705148
A. thailandicum MFLUCC 15-0199 Dead culms of bamboo Thailand KU940146 KU863134 - -
A. thailandicum MFLUCC 15-0202 Dead culms of bamboo Thailand KU940145 KU863133 - -
A. trachycarpum CFCC 53038 Dead branches of Trachycarpus fortune China MK301098 - MK303394 MK303396
A. trachycarpum CFCC 53039 Dead branches of Trachycarpus fortune China MK301099 - MK303395 MK303397
A. urticae IMI 326344 - - AB220245 AB220339 AB220292 -
A. vietnamense IMI 99670 Citrus sinensis Vietnam KX986096 KX986111 KY019466 -
A. xenocordella CBS 478.86 Soil from roadway Zimbabwe KF144925 KF144970 KF145013 KF145055
A. xenocordella CBS 595.66 Soil Austria KF144926 KF144971 - -
A. yunnanum DDQ00281 Dead culms of Phyllostachys nigra China KU940148 KU863136 - -
A. yunnanum MFLUCC 15-1002 Dead culms of Phyllostachys nigra China KU940147 KU863135 - -
Seiridium phylicae CPC 19962 Phylica arborea UK LT853092 KC005807 LT853239 LT853189
Seiridium phylicae CPC 19965 Phylica arborea UK LT853093 KC005809 LT853240 LT853190

Notes: Newly-generated sequences are indicated by ▲ after the species name. Ex-type strains are in bold. Abbreviations: AMH: Ajrekar Mycological Herbarium, Pune, Maharashtra, India; CBS: Westerdijk Fungal Biodiversity Institute, Utrecht, Netherlands; CFCC: China Forestry Culture Collection Center, Beijing, China; CPC: Culture collection of Pedro Crous, housed at the Westerdijk Fungal Biodiversity Institute; DAOM: Canadian Collection of Fungal Cultures, Ottawa, Canada; DDQ: D.Q. Dai; ICMP: International Collection of Microorganisms from Plants, New Zealand; IFO: Institute for Fermentation, Osaka, Japan; IMI: Culture collection of CABI Europe UK Centre, Egham, UK; JHB: H.B. Jiang; KUMCC: Culture collection of Kunming Institute of Botany, Yunnan, China; LC: personal culture collection of Lei Cai, housed in the Institute of Microbiology, Chinese Academy of Sciences, China; MFLUCC: Mae Fah Luang University Culture Collection, Chiang Rai, Thailand; NFCCI: National Fungal Culture Collection of India.

Phylogenetic analyses were performed using the CIPRES Science Gateway web portal (Miller et al. 2010). ML was done using the RAxML-HPC on XSEDE tool under the GTRGAMMA+I-Invar substitution model (Stamatakis et al. 2008). MP analysis was performed using the PAUP on XSEDE tool (Swofford 2002). A heuristic search with 1000 random taxa additions was used to infer MP trees. The value of MaxTrees was set to 5000, with branches of zero length collapsed and all multiple parsimonious trees saved. Parsimony score values for tree length (TL), consistency index (CI), retention index (RI) and homoplasy index (HI) were calculated for trees generated under different optimum criteria. Robustness of branches was estimated by maximum parsimony bootstrap proportions, using 100 bootstrap replicates, with tree bisection-reconnection branch swapping and a re-arrangement limit of 1000.

BI analysis was performed using the MrBayes on XSEDE tool available on the CIPRES Science Gateway (Huelsenbeck and Ronquist 2001, Miller et al. 2010, Ronquist et al. 2012). The best-fit model for each locus was selected by MrModeltest version 2.3, under the Akaike Information Criterion. Four Markov Chain Monte Carlo (MCMC) chains were run, starting from a random tree topology. The operation was stopped automatically when the average standard deviation of split frequencies fell below 0.01. Markov chains were set to run 10,000,000 generations with sampling every 1000 generations. A burn-in set at 25% was discarded. The Maximum Clade Credibility tree was inferred with the highest product of separate clade posterior probabilities (PP). Trees were visualised in FigTree version 1.4.0 and edited with Adobe Illustrator v. 51.1052.0.0 (Adobe Inc., San Jose, California, USA).

Taxon treatment

Arthrinium bambusicola X. Tang, K.D. Hyde & J.C. Kang, 2020, sp. nov.

Material    Download as CSV 
Holotype:
  1. scientificName:
    Arthrinium bambusicola
    ; kingdom:
    Fungi
    ; phylum:
    Ascomycota
    ; class:
    Sordariomycetes
    ; order:
    Amphisphaeriales
    ; family:
    Apiosporaceae
    ; genus:
    Arthrinium
    ; country:
    Thailand
    ; countryCode:
    TH
    ; stateProvince:
    Chiang Rai
    ; locality:
    Mae Fah Luang University
    ; year:
    2019
    ; month:
    May
    ; day:
    7
    ; habitat:
    terrestrial
    ; fieldNotes:
    on dead culms of Schizostachyum brachycladum
    ; recordedBy:
    Xia Tang
    ; identifiedBy:
    Xia Tang
    ; dateIdentified:
    2019
    ; type:
    Holotype
    ; collectionID:
    MFLU 20-0528
    ; collectionCode:
    M19050706

Description

Saprobic on dead culms of Schizostachyum brachycladum (Poales, Poaceae, Bambusoideae). Sexual morph: Undetermined. Asexual morph: Colonies on natural substrate, superficial, gregarious, scattered, irregular, dark brown to black (Fig. 1a-b). Mycelium consisting of branched, septate, hyaline to dark brown (Fig. 1c-e). Conidiophores 0.8–3.5 μm diam. semi-micronematous to macronematous, mononematous, solitary, branched, flexuous, smooth, hyaline, aseptate when immature, becoming brown, septate when mature (Fig. 1d). Conidiogenous cells 1.5–4.5 × 1–4 μm, monoblastic or polyblastic, terminal, determinate, cylindrical, hyaline to light brown, smooth, aggregated, ampulliform, in clusters on aerial mycelium (Fig. 1e-g). Conidia pleurogenous, solitary, oval to broadly round or irregularly round, brown to medium brown, guttulate to roughened, granular, in surface view 6–8 × 6–7.8 μm ( = 6.5 × 7 μm, n = 39), in lateral view 3.5–6 × 3.5–6.5 μm ( = 4.5 × 5 μm, n = 39), with finely pale slit at outer edge (Fig. 1h-l).

Figure 1.  

Arthrinium bambusicola (MFLU 20-0528, holotype). a, b. Appearance of the fungus on dead culms of Schizostachyum brachycladum; c. Conidia with mycelia; d. Mycelia; e–f. Mycelia bearing conidiogenous cells and conidia; h–l. Conidia; m. Germinated conidium; n. forward culture; o. reversed culture. Scale bars: b = 500 μm, c–e = 20 μm, f, g = 10 μm, h–m = 5 μm.

Culture characteristics: 

colonies flat, spreading, with moderate, pale, aerial mycelium. On PDA, surface white, lightly yellow with patches of dirty white, reverse lightly pigmented.

Facesoffungi number: 

FoF 09162

Etymology: 

Referring to the host from which the holotype was isolated, a member of the bamboo subfamily (Bambusoideae).

Notes: 

Arthrinium bambusicola forms were retrieved as a sister taxon of A. gutiae, with relatively good support (83 ML, 77 MP, 0.99 PP). Morphologically, A. bambusicola differs from A. gutiae in having larger conidia [surface view: 5.5–8 × 6–8 μm diam., lateral view: 3.5–6 × 3.5–6.5 μm diam. versus surface view: 4.5–6 μm ( = 5.5 μm) diam., lateral view: 2–6 μm ( = 4) diam.] and irregularly rounded, guttulate to roughened conidia (A. gutiae: smooth-walled, globose conidia). The conidiogenous cells of A. bambusicola are smaller (1.5–4.5 × 1–4 μm versus 3–7× 2–4 μm). Based on pairwise nucleotide comparisons, A. bambusicola is different from A. gutiae in 31/ 620 bp (5%) of the ITS, 7/814 (0.98%) of the LSU and 44/342 bp (12%) of TEF1. Based on the combination of morphological characters and sequence data, we consider A. bambusicola as a distinct species.

Analysis

Phylogenetic analyses

The concatenated ITS–LSU–TEF1–TUB2 dataset consisted of 98 taxa with Seiridium phylicae (Sporocadaceae), isolates CPC 19962 and CPC 19965, as the outgroup. The data matrix consisted of 2414 total characters including gaps, of which 1126 were parsimony-informative (LSU: 1–812 bp, ITS: 813–1264 bp, TEF1: 1265–1688 bp, TUB2: 1689–2414 bp). MP (Suppl. material 3), ML (Suppl. material 4) and BI (Suppl. material 2) analyses of the concatenated dataset resulted in largely similar tree topologies. The best-scoring RaxML tree (-lnL = 25256.155227) is presented in Figs 2, 3. The most parsimonious tree showed the following values: TL = 4653, CI = 0.490, RI = 0.808, RC = 0.396 and HI = 0.510. For the Bayesian posterior probabilities analysis, the best-fit models were selected as GTR+I+G for ITS and LSU and HKY+I+G for TEF1 and TUB2; 2,895,000 generations were run. A total of 2172 trees were maintained after discarding 25% as burn-in. Bayesian PP were evaluated with a final average standard deviation of split frequencies of 0.009965.

Figure 2.  

Figs 2, 3 The best-scoring RAxML tree reconstructed from a concatenated ITS–LSU–TEF1–TUB2 dataset. The tree is rooted with Seiridium phylicae (strains CPC 19962 and CPC 19965). ML and MP bootstrap values ≥ 70 and Bayesian PP ≥ 0.95 are shown at the nodes (ML/MP/PP). Ex-type strains are in bold; the newly-described species is highlighted in red.

Figure 3.  

Figure 2 Continued.

Discussion

The family Apiosporaceae was introduced by Hyde et al. (1998) to accommodate Apiospora and Appendicospora, based on their unique morphology. Arthrinium is one of the asexual morphs of Apiospora, along with Cordella and Pteroconium (Hyde et al. 1998). Based on molecular evidence, Crous and Groenewald (2013) confirmed that the genus Arthrinium belongs to Apiosporaceae (Hyde et al. 2020b, Wijayawardene et al. 2020). Apiospora was shown to be synonymous with Arthrinium, which is the oldest name (Hawksworth et al. 2011, Crous and Groenewald 2013).

Arthrinium species have a highly-variable morphology (Crous and Groenewald 2013, Dai et al. 2017). They produce hyphomycetous fungal structures in culture or coelomycetous fruiting bodies on their host, depending on the substrate and period of incubation (Crous and Groenewald 2013, Dai et al. 2017). However, as more species of Arthrinium are discovered, identification, based on morphology alone, has become very difficult because some species exhibit similar micro-morphological characters (Jiang et al. 2019).

ITS sequence data provide limited resolution to distinguish species for some Arthrinium species, for example, in the case of A. phyllostachium and A. vietnamensis. The ITS sequences of these species are > 99% similar. However, both species can be distinguished using the secondary barcodes TEF1 and TUB2 (Wang et al. 2018, Yang et al. 2019). In our phylogenetic analyses, A. neogarethjonesii (Hyde et al. 2020b) and A. setostromum (Jiang et al. 2019) cluster together with strong support (97 ML/96 MP/1 PP). Again, the ITS sequences of these species are > 99% similar. However, some morphological characters can be used to separate these two taxa. Whereas A. neogarethjonesii lacks setae, A. setostromum bears setae on the surface of the stromata. The former has larger stromata [1000–2000 μm × 175–250 μm versus 250–600 μm × 140–180 μm] and asci [95–125 μm × 20–25 μm versus 82.5–102.5 μm × 20–30 μm], smaller ascomata [120–230 μm × 125–230 μm versus 210–260 μm × 100–170 μm] and conidiogenous cells [10–48 μm × 4–5.5 μm versus 42–66 μm × 1.5–2.7 μm]. In their asexual morphs, A. setostromum has micronematous, holoblastic and monoblastic conidiogenous cells, but A. neogarethjonesii has basauxic conidiogenous cells. For A. neogarethjonesii, only ITS and LSU sequences are available; for A. setostromum, also a TEF1 sequence is available. Fresh collections of A. neogarethjonesii are necessary to generate sequences of the protein-coding genes for improved species delimitation (Hyde et al. 2020c).

Arthrinium species have been reported from soil debris, plants, lichens, marine algae and hive-stored pollen (Senanayake et al. 2015, Wijayawardene et al. 2017, Zhao et al. 2018), in the gut of insects (Crous et al. 2015), in nodules of human skin (Sharma et al. 2014) and especially associated with bamboo. To date, 24 Arthrinium species have been found in association with the bamboo subfamily Bambusoideae (Dai et al. 2016, Dai et al. 2017, Jiang et al. 2018, Wang et al. 2018, Jiang et al. 2019, Yang et al. 2019, Jiang et al. 2020, https://nt.ars-grin.gov/fungaldatabases/). Arthrinium species have been reported from all continents, except Antarctica (Ellis 1963, Dyko and Sutton 1979, Calvo and Guarro 1980, Von Arx 1981, Crous and Groenewald 2013, Sharma et al. 2014, Wang et al. 2018, Jiang et al. 2020).

To date, seven species of Arthrinium have been reported from Thailand. These are A. bambusicola (this study), A. chromolaenae (Mapook et al. 2020), A. longistromum (Dai et al. 2017), A. paraphaeospermum (Hyde et al. 2016), A. rasikravindrii (Dai et al. 2017), A. subglobosum (Senanayake et al. 2015) and A. thailandicum (Dai et al. 2017). Contrasting morphological features amongst these species are presented in Suppl. material 1. Six of the seven Thai species are found in association with bamboo: Arthrinium bambusicola, A. longistromum, A. paraphaeospermum, A. rasikravindrii , A. subglobosum and A. thailandicum (Senanayake et al. 2015, Hyde et al. 2016, Dai et al. 2017). Only Arthrinium chromolaenae was reported from a non-bamboo host, Chromolaena odorata (Asterales, Asteraceae) (Mapook et al. 2020). Further studies on this genus in Thailand and other countries, as well as from different hosts, are likely to result in the discovery of more new species (Hyde et al. 2018, Hyde et al. 2020a).

Acknowledgements

This work was funded by grants of the National Natural Science Foundation of China (NSFC Grants nos. 31670027 & 31460011). The authors are grateful to the Thailand Research Fund grant “Impact of climate change on fungal diversity and biogeography in the Greater Mekong Sub-region” (RDG6130001). Shaun Pennycook is thanked for his suggestions on naming the new fungus. The authors would also like to thank Mae Fah Luang University.

References

Supplementary materials

Suppl. material 1: Morphological comparison of the seven Arthrinium species introduced from Thailand 
Authors:  Xia Tang, Ishani D. Goonasekara, Ruvishika S. Jayawardena, Hong B. Jiang, Jun F. Li, Kevin D. Hyde, Ji C. Kang
Data type:  Morphological comparison
Brief description: 

The morphological comparison of seven Arthrinium species introduced from Thailand.

Suppl. material 2: BI output file 
Authors:  Xia Tang
Data type:  Phylogenetic output file for BI
Brief description: 

The output file of BI

Suppl. material 3: MP output file 
Authors:  Xia Tang
Data type:  The phylogenetic output file of MP
Suppl. material 4: The output file of ML 
Authors:  Xia Tang
Data type:  The phylogenetic output file of ML