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New species in Dictyosporium, new combinations in Dictyocheirospora and an updated backbone tree for Dictyosporiaceae
expand article infoJing Yang§, Jian-Kui Liu§, Kevin D. Hyde|, E.B. Gareth Jones#, Zuo-Yi Liu§
‡ Mae Fah Luang University, Chiang Rai, Thailand
§ Guizhou Key Laboratory of Agricultural Biotechnology, Guizhou Academy of Agricultural Sciences, Guiyang, China
| World Agroforestry Centre, Kunming, China
¶ Kunming Institute of Botany, Chinese Academy of Science, Kunming, China
# Chiang Mai University, Chiang Mai, Thailand
Open Access

Abstract

A survey of freshwater fungi on submerged wood in China and Thailand resulted in the collection of three species in Dictyocheirospora and four species in Dictyosporium including two new species in the latter genus. Morphological characters and phylogenetic analyses based on ITS, LSU and TEF1α sequence data support their placement in Dictyocheirospora and Dictyosporium (Dictyosporiaceae). An updated backbone tree is provided for the family Dictyosporiaceae. Descriptions and illustrations of the new taxa and re-collections are provided. Four new combinations are proposed for Dictyocheirospora.

Keywords

2 new taxa, asexual morph, Dothideomycetes, phylogeny, taxonomy

Introduction

The family Dictyosporiaceae was introduced by Boonmee et al. (2016) to accommodate mostly aquatic lignicolous species with cheiroid, digitate, palmate and/or dictyosporous conidia and their sexual morphs that form a monophyletic clade in the class Dothideomycetes.

Dictyosporium, the type genus of the family, has been reported worldwide from dead wood and plant litter in terrestrial and aquatic habitats (Hyde and Goh 1998, Ho et al. 2002, Pinnoi et al. 2006, Pinruan et al. 2007). Corda (1836) established the genus with D. elegans Corda as the type species. The holomorph genus is characterised by dark brown, subglobose superficial ascomata, bitunicate cylindrical asci and hyaline, fusiform uniseptate ascospores with or without a sheath; sporodochial colonies, micronematous to macronematous conidiophores and cheiroid, digitate complanate conidia with several parallel rows of cells. Goh et al. (1999) reviewed the genus accepting 22 species and the remaining 16 species were doubtful or excluded. Tsui et al. (2006) first considered that the genus is closely related to Massarinaceae (Pleosporales) based on phylogenetic analysis using SSU and LSU sequence data. Tanaka et al. (2015) and Boonmee et al. (2016) confirmed the phylogenetic placement of Dictyosporium in Dictyosporiaceae (Massarineae, Pleosporales). Recent comparisons of Dictyosporium species were provided by Whitton et al. (2012), Prasher and Verma (2015) and Silva et al. (2015) with up to 48 accepted species. Since Silva et al. (2015), D. araucariae S.S. Silva, R.F. Castañeda & Gusmão, D. hydei I.B. Prasher & R.K. Verma, D. indicum I.B. Prasher & R.K. Verma, D. olivaceosporum Kaz. Tanaka, K. Hiray., Boonmee & K.D. Hyde, D. palmae Abdel-Aziz, D. pseudomusae Kaz. Tanaka, G. Sato & K. Hiray., D. sexualis Boonmee & K.D. Hyde, D. splendidum Alves-Barb., Malosso & R.F. Castañeda and D. wuyiense Y. Zhang & G.Z. Zhao were newly introduced to the genus (Prasher and Verma 2015, Tanaka et al. 2015, Abdel-Aziz 2016, Boonmee et al. 2016, da Silva et al. 2016, Alves-Barbosa et al. 2017, Zhang et al. 2017) and nine species were re-assigned to Dictyocheirospora, Jalapriya and Vikalpa (Boonmee et al. 2016). Wijayawardene et al. (2017a) provided information on the availability of cultures and references to accessible sequence data.

Dictyocheirospora was introduced by Boonmee et al. (2016) with Di. rotunda D’souza, Bhat & K.D. Hyde as the type species. Dictyocheirospora is morphologically similar to Dictyosporium except in having cheiroid, non-complanate or cylindrical conidia, mostly with conidial arms closely gathered together at the apex. Ten species are accepted in the genus including four species transferred from Dictyosporium (Boonmee et al. 2016, Wang et al. 2016, Hyde et al. 2017, Li et al. 2017).

During a survey of freshwater fungi on submerged wood along a north/south gradient in the Asian/Australasian region (Hyde et al. 2016), two new freshwater species and five previously described species were collected and identified based on phylogenetic analyses and morphological characters. We therefore introduce Dictyosporium tubulatum and Dictyosporium tratense as new species, with an illustrated account and phylogenetic evidence for the new taxa. An updated backbone tree based on the combined ITS, LSU and TEF1α sequence data is provided for Dictyosporiaceae. Four new combinations are proposed in Dictyocheirospora.

Materials and methods

Collection and examination of specimens

Specimens of submerged, decaying wood were collected from streams in Chiang Rai, Prachuap Khiri Khan, Phang Nga and Trat Provinces, Thailand, in December 2014, 2015, April 2016 and Guizhou Province, China, in October 2016. Specimens were brought to the laboratory in plastic bags and incubated in plastic boxes lined with moistened tissue paper at room temperature for one week. Morphological observations were made using a Motic SMZ 168 Series dissecting microscope for fungal structures on natural substrate. The fungal structures were collected using a syringe needle and transferred to a small drop of distilled water on a clean slide and covered with a cover glass. The fungi were examined using a Nikon ECLIPSE 80i compound microscope and photographed with a Canon 550D, 600D or 70D digital camera fitted to the microscope. Measurements were made with the TAROSOFT (R) IMAGE FRAME WORK programme and images used for figures were processed with ADOBE PHOTOSHOP CS6 software. Single spore isolations were made on to potato dextrose agar (PDA) or water agar (WA) and later transferred on to malt extract agar (MEA) or PDA following the method of Chomnunti et al. (2014). Specimens (dry wood with fungal material) are deposited in the herbarium of Mae Fah Luang University (MFLU), Chiang Rai, Thailand and Kunming Institute of Botany, Academia Sinica (HKAS), China. Axenic cultures are deposited in Mae Fah Luang University Culture Collection (MFLUCC). Facesoffungi and Index Fungorum numbers are registered as outlined in Jayasiri et al. (2015) and Index Fungorum (2018).

DNA extraction, PCR amplification and sequencing

Isolates were grown on PDA and/or MEA medium at 25 °C for one month. Fungal mycelium was scraped off and transferred to a 1.5-ml microcentrifuge tube using a sterilised lancet for genomic DNA extraction. Ezup Column Fungi Genomic DNA Purification Kit (Sangon Biotech, China) was used to extract DNA following the manufacturer’s instructions. ITS, LSU and TEF1α gene regions were amplified using the primer pairs ITS5 or ITS1 with ITS4 (Vilgalys and Hester 1990), LROR with LR5 or LR7 (White et al. 1990) and EF1-983F with EF1-2218R (Rehner 2001). The amplifications were performed in a 25 μl reaction volume containing 9.5 μl ddH2O, 12.5 μl 2 × Taq PCR Master Mix with blue dye (Sangon Biotech, China), 1 μl of DNA template and 1 μl of each primer (10 μM). The amplification condition for ITS, LSU and TEF1α consisted of initial denaturation at 94 °C for 3 min; followed by 40 cycles of 45 s at 94 °C, 50 s at 56 °C and 1 min at 72 °C and a final extension period of 10 min at 72 °C. Purification and sequencing of PCR products were carried out using the above-mentioned PCR primers at Sangon Biotech (Shanghai) Co. Ltd. in China.

Phylogenetic analyses

The taxa included in the phylogenetic analyses were selected and obtained from previous studies and GenBank (Boonmee et al. 2016, Wang et al. 2016, Li et al. 2017). Three gene regions (ITS, LSU and TEF1α) were used for the combined sequence data analyses. SEQMAN v. 7.0.0 (DNASTAR, Madison, WI) was used to assemble consensus sequences. The sequences were aligned using the online multiple alignment programme MAFFT v.7 (http://mafft.cbrc.jp/alignment/server/) (Katoh and Standley 2013). The alignments were checked visually and improved manually where necessary.

Phylogenetic analysis of the sequence data consisted of maximum likelihood (ML) using RAxML-HPC v.8 (Stamatakis 2006, Stamatakis et al. 2008) on the XSEDE Teragrid of the CIPRES science Gateway (https://www.phylo.org) (Miller et al. 2010) with rapid bootstrap analysis, followed by 1000 bootstrap replicates. The final tree was selected amongst suboptimal trees from each run by comparing likelihood scores under the GTRGAMMA substitution model.

Maximum parsimony (MP) analyses were performed with PAUP v. 4.0b10 (Swofford 2003) using the heuristic search option with 1000 random taxa addition and tree bisection and reconnection (TBR) as the branch swapping algorithm. All characters were unordered and of equal weight and gaps were treated as missing data. Maxtrees were unlimited, branches of zero length were collapsed and all multiple, equally parsimonious trees were saved. Clade stability was assessed using a bootstrap (BT) analysis with 1000 replicates, each with 10 replicates of random stepwise addition of taxa (Hillis and Bull 1993).

The programme MRMODELTEST2 v. 2.3 (Nylander 2008) was used to infer the appropriate substitution model that would best fit the model of DNA evolution for the combined datasets for Bayesian inference analysis with GTR+G+I substitution model selected. Posterior probabilities (PP) (Rannala and Yang 1996, Zhaxybayeva and Gogarten 2002) were determined by Markov Chain Monte Carlo sampling (MCMC) in MRBAYES v. 3.0b4 (Huelsenbeck and Ronquist 2001). Six simultaneous Markov chains were run for 1 million generations, with trees sampled every 100 generations (resulting in 10000 trees). The first 2000 trees, representing the burn-in phase of the analyses were discarded and the remaining 8000 trees were used for calculating posterior probabilities (PP) in the majority rule consensus tree (Larget and Simon 1999).

The resulting trees were printed with FIGTREE v. 1.4.0 (http://tree.bio.ed.ac.uk/software/figtree/) and the layout was created in MICROSOFT POWERPOINT for Mac v. 15.19.1. The alignment of phylogenetic analyses and resultant tree were deposited in TreeBASE (www.treebase.org, submission number 22802). Sequences generated in this study were submitted to GenBank (Table 1).

Isolates and sequences used in this study (newly generated sequences are indicated in bold, ex-type strains are indicated with T after strain number).

Species Source GenBank accession number
ITS LSU TEF1α
Aquadictyospora lignicola MFLUCC 17-1318T MF948621 MF948629 MF953164
Aquaticheirospora lignicola HKUCC 10304T AY864770 AY736378
Cheirosporium triseriale HMAS 180703T EU413953 EU413954
Dendryphiella eucalyptorum CBS 137987T KJ869139 KJ869196
Dendryphiella fasciculata MFLUCC 17-1074T MF399213 MF399214
Dendryphiella paravinosa CBS 141286T KX228257 KX228309
Dictyocheirospora aquatica KUMCC 15-0305T KY320508 KY320513
Dictyocheirospora bannica KH 332T LC014543 AB807513 AB808489
Dictyocheirospora bannica MFLUCC 16-0874 MH381765 MH381774
Dictyocheirospora garethjonesii MFLUCC 16-0909T KY320509 KY320514
Dictyocheirospora garethjonesii DLUCC 0848 MF948623 MF948631 MF953166
Dictyocheirospora gigantica BCC 11346 DQ018095
Dictyocheirospora heptaspora CBS 396.59 DQ018090
Dictyocheirospora indica MFLUCC 15-0056 MH381763 MH381772 MH388817
Dictyocheirospora pseudomusae yone 234T LC014550 AB807520 AB808496
Dictyocheirospora rotunda MFLUCC 14-0293T KU179099 KU179100
Dictyocheirospora rotunda MFLUCC 17-0222 MH381764 MH381773 MH388818
Dictyocheirospora rotunda MFLUCC 17-1313 MF948625 MF948633 MF953168
Dictyocheirospora subramanianii BCC 3503 DQ018094
Dictyocheirospora vinaya MFLUCC 14-0294T KU179102 KU179103
Dictyosporium alatum ATCC 34953T NR_077171 DQ018101
Dictyosporium aquaticum MF 1318T KM610236
Dictyosporium bulbosum yone 221 LC014544 AB807511 AB808487
Dictyosporium digitatum KH 401 LC014545 AB807515 AB808491
Dictyosporium digitatum yone 280 LC014547 AB807512 AB808488
Dictyosporium elegans NBRC 32502T DQ018087 DQ018100
Dictyosporium hughesii KT 1847 LC014548 AB807517 AB808493
Dictyosporium meiosporum MFLUCC 10-0131T KP710944 KP710945
Dictyosporium nigroapice BCC 3555 DQ018085
Dictyosporium nigroapice MFLUCC 17-2053 MH381768 MH381777 MH388821
Dictyosporium olivaceosporum KH 375T LC014542 AB807514 AB808490
Dictyosporium sexualis MFLUCC 10-0127T KU179105 KU179106
Dictyosporium sp. MFLUCC 15-0629 MH381766 MH381775 MH388819
Dictyosporium stellatum CCFC 241241T NR_154608 JF951177
Dictyosporium strelitziae CBS 123359T NR_156216 FJ839653
Dictyosporium tetrasporum KT 2865 LC014551 AB807519 AB808495
Dictyosporium thailandicum MFLUCC 13-0773T KP716706 KP716707
Dictyosporium tratense MFLUCC 17-2052T MH381767 MH381776 MH388820
Dictyosporium tubulatum MFLUCC 15-0631T MH381769 MH381778 MH388822
Dictyosporium tubulatum MFLUCC 17-2056 MH381770 MH381779
Dictyosporium wuyiense CGMCC 3.18703T KY072977
Dictyosporium zhejiangense MW-2009aT FJ456893
Digitodesmium bambusicola CBS 110279T DQ018091 DQ018103
Gregarithecium curvisporum KT 922T AB809644 AB807547
Jalapriya inflata NTOU 3855 JQ267362 JQ267363
Jalapriya pulchra MFLUCC 15-0348T KU179108 KU179109
Jalapriya pulchra MFLUCC 17-1683 MF948628 MF948636 MF953171
Jalapriya toruloides CBS 209.65 DQ018093 DQ018104
Periconia igniaria CBS 379.86 LC014585 AB807566 AB808542
Periconia igniaria CBS 845.96 LC014586 AB807567 AB808543
Pseudocoleophoma calamagrostidis KT 3284T LC014592 LC014609 LC014614
Pseudocoleophoma polygonicola KT 731T AB809634 AB807546 AB808522
Pseudocoleophoma typhicola MFLUCC 16-0123T KX576655 KX576656
Pseudodictyosporium elegans CBS 688.93T DQ018099 DQ018106
Pseudodictyosporium indicum CBS 471.95 DQ018097
Pseudodictyosporium thailandica MFLUCC 16-0029T KX259520 KX259522 KX259526
Pseudodictyosporium wauense NBRC 30078 DQ018098 DQ018105
Pseudodictyosporium wauense DLUCC 0801 MF948622 MF948630 MF953165
Vikalpa australiensis HKUCC 8797T DQ018092

Phylogenetic results

The analysed dataset consisted of combined ITS (557 bp), LSU (803 bp) and TEF1α (918 bp) sequence data (a total of 2278 characters including gaps) for 59 taxa in Dictyosporiaceae with Periconia igniaria E.W. Mason & M.B. Ellis (CBS 379.86, CBS 845.96) as the outgroup taxon. The best scoring RAxML tree is shown in Figure 1.

Figure 1. 

Maximum likelihood majority rule consensus tree for the analysed Dictyosporiaceae isolates based on a dataset of combined ITS, LSU and TEF1α sequence data. Bootstrap support values for maximum likelihood (ML) and maximum parsimony (MP) greater than 75% and Bayesian posterior probabilities greater than 0.95 are indicated above the nodes as MLBS/MPBS/PP. The scale bar represents the expected number of changes per site. The tree is rooted with Periconia igniaria (CBS 379.86, CBS 845.96). The strain numbers are noted after the species names with ex-type strains indicated with T. The new collections are in bold with new taxa in red. Branches with 100% ML BS, 100% MP BS and 1.0 PP are shown as black nodes. Genera are indicated as coloured blocks.

Phylogenetic analyses indicated the placement of three isolates (MFLUCC 15-0056, MFLLUCC 16-0874 and MFLUCC 17-0222) within the genus Dictyocheirospora. Five isolates (MFLUCC 15-0629, MFLUCC 17-2052, MFLUCC 17-2056, MFLUCC 15-0631 and MFLUCC 17-2053) nested in Dictyosporium. Phylogenetic results showed that Dictyocheirospora indica (MFLUCC 15-0056) clustered with Dictyocheirospora subramanianii (B. Sutton) D'souza, Boonmee & K.D. Hyde (BCC 3503) with good support. Dictyocheirospora bannica (MFLUCC 16-0874) was placed as sister taxon to the ex-type strain Dictyocheirospora bannica (KH 332). Dictyocheirospora rotunda (MFLUCC 17-0222) grouped together with Dictyocheirospora rotunda (MFLUCC 17-1313) and the ex-type strain Dictyocheirospora rotunda (MFLUCC 14-0293) with strong support. The strain Dictyosporium sp. (MFLUCC 15-0629) clustered as sister taxon to Dictyosporium digitatum J.L. Chen, C.H. Hwang & Tzean (KH 401), Dictyosporium aquaticum Abdel-Aziz (MF 1318) and Dictyosporium stellatum G.P. White & Seifert (CCFC 241241). The new taxon Dictyosporium tratense (MFLUCC 17-2052) formed a single clade within Dictyosporium which is distinct from other species in the genus. The new collection Dictyosporium nigroapice (MFLUCC 17-2053) was placed as sister taxon to a previous isolate Dictyosporium nigroapice (BCC 3555). Two isolates of the new taxon Dictyosporium tubulatum (MFLUCC 15-0631 and MFLUCC 17-2056) nested in Dictyosporium as sister clade to Dictyosporium nigroapice (MFLUCC 17-2053 and BCC 3555).

Taxonomy

Dictyocheirospora species

Dictyocheirospora bannica Kaz. Tanaka, K. Hiray., Boonmee & K.D. Hyde, Fungal Diversity 80: 467 (2016)

Index Fungorum number: IF551997
Facesoffungi number: FoF02014
Figure 2

Material examined

THAILAND. Phang Nga Province, Bann Tom Thong Khang, on decaying wood submerged in a freshwater stream, 17 Dec 2015, J. Yang, Site 7-70-1 (MFLU 18-1040, HKAS 102131), living culture MFLUCC 16-0874 (Additional SSU sequence GenBank MH381759).

Notes

The phylogenetic result showed the strain MFLUCC 16-0874 clustered with the ex-type (KH 332) of Dictyocheirospora bannica. The morphological examination of this collection matched well with the holotype of Dictyocheirospora bannica (Boonmee et al. 2016). Dictyocheirospora bannica was previously collected in Japan, while this is a new record for Thailand.

Figure 2. 

Dictyocheirospora bannica (MFLU 18-1040) a Colonies on submerged wood b Conidia and conidiophores c–f Conidia g Germinated conidium h, i Culture, h from above, i from reverse. Scale bars: a = 200 μm, b, g = 50 μm, c–f = 30 μm.

Dictyocheirospora hydei (I.B. Prasher & R.K. Verma) J. Yang & K.D. Hyde, comb. nov.

Index Fungorum number: IF554773
Facesoffungi number: FoF04679

Basionym

Dictyosporium hydei I.B. Prasher & R.K. Verma, Phytotaxa 204 (3): 196 (2015).

Holotype

INDIA. Himachal Pradesh, Bilaspur, on bark of Tecoma stans, 17 September 2013, I.B. Prasher and R.K. Verma (PAN 30364).

Notes

Considering the latest generic concept of Dictyocheirospora and Dictyosporium, we suggest that Dictyosporium hydei should be referred to Dictyocheirospora with the key character of non-complanate or cylindrical conidia with conidial arms closely gathered together at the apex. We have not examined the holotype of Dictyocheirospora hydei. The details provided by Prasher and Verma (2015) are adequate being illustrative and descriptive.

Dictyocheirospora indica (I.B. Prasher & R.K. Verma) J. Yang & K.D. Hyde, comb. nov.

Index Fungorum number: IF554774
Facesoffungi number: FoF04680
Figure 3

Basionym

Dictyosporium indicum I.B. Prasher & R.K. Verma, Phytotaxa 204 (3): 194 (2015).

Holotype

INDIA. Himachal Pradesh, Mandi, on petiole of Phoenix rupicola, 19 November 2012, I.B. Prasher and R.K. Verma (PAN 30313).

Material examined

THAILAND. Chiang Rai, stream flowing in Tham Luang Nang Non Cave, on decaying submerged wood, 25 November 2014, J. Yang, YJ-3 (MFLU 15-1169 reference specimen designated here, HKAS 102135), living culture MFLUCC 15-0056 (Additional SSU sequence GenBank MH381757).

Notes

Collection MFLU 15-1169 was identified as Dictyocheirospora indica (Dictyosporium indicum) based on morphological examination. Phylogenetic analyses indicated the placement of this taxon within Dictyocheirospora and sister to Di. subramanianii (BCC 3503). Dictyocheirospora subramanianii differs from Di. indica in lacking appendages. Dictyocheirospora indica resembles Di. musae in having non-complanate, cylindrical conidia with globose to subglobose appendages. However, conidial appendages of Di. indica are attached at the subapical cells, while appendages of Di. musae are attached at the central cells of the outer cell-row. The conidial size of Di. indica (33–48 × 13–18 µm) is smaller than that of Di. musae (45–65 × 20–27 µm) (Photita et al. 2002, Prasher and Verma 2015). In this study, sequence data of our collection Dictyocheirospora indica (MFLUCC 15-0056) was generated and, as there is no sequence data available for the previous collection (Dictyosporium indicum), we therefore designated our collection as the reference specimen (sensu Ariyawansa et al. 2014) for Dictyocheirospora indica.

Figure 3. 

Dictyocheirospora indica (MFLU 15-1169, reference specimen). a Substrate b, c Colonies on woody substrate d, e Conidial formation f–i Conidia with partial conidiophores j–o Conidia p Germinated conidium q–r Culture, q from above, r from reverse. Scale bars: b = 200 μm, c = 100 μm, d–i, l–o = 20 μm, j = 10 μm, k = 15 μm, p = 30 μm.

Dictyocheirospora musae (Photita) J. Yang, K.D. Hyde & Z.Y. Liu, comb. nov.

Index Fungorum number: IF554775
Facesoffungi number: FoF04681

Basionym

Dictyosporium musae Photita, Mycotaxon 82: 416 (2002)

Holotype

THAILAND. Mae Hong Son Province, Sob Mei, Huay Thicha Village, on decaying petioles of Musa acuminata, 23 November 2000, W. Photita (PDD 74135).

Notes. Dictyocheirospora musae is morphologically similar to Di. hydei in having non-complanate, cylindrical conidia with globose to subglobose appendages. However, Dictyocheirospora musae differs in having appendages in the middle cells while Di. hydei has appendages on the basal cells (Photita et al. 2002, Prasher and Verma 2015).

Dictyocheirospora rotunda D’souza, Bhat & K.D. Hyde, Fungal Diversity 80: 465 (2016)

Index Fungorum number: IF551581
Facesoffungi number: FoF01262
Figure 4

Material examined

CHINA. Guizhou Province, Anshun city, Gaodang village, 26°4.267'N, 105°41.883'E, on decaying wood submerged in Suoluo river, 19 October 2016, J. Yang, GD 2-3 (MFLU 18-1041, HKAS 102132), living culture MFLUCC 17-0222 (Additional SSU sequence GenBank MH381758).

Notes

This species is known in China and Thailand from freshwater habitats (Boonmee et al. 2016, Wang et al. 2016).

Figure 4. 

Dictyocheirospora rotunda (MFLU 18-1041). a Colonies on submerged wood b, c Germinated conidia d Conidia e, f Culture, e from above, f from reverse. Scale bars: a = 200 μm, b, c = 20 μm, d = 50 μm.

Dictyocheirospora tetraploides (L. Cai & K.D. Hyde) J. Yang & K.D. Hyde, comb. nov.

Index Fungorum number: IF554776
Facesoffungi number: FoF04682

Basionym

Dictyosporium tetraploides L. Cai & K.D. Hyde, Sydowia 55 (2): 132 (2003)

Holotype

CHINA. Yunnan, Xishuangbanna, Menglun, a small stream, on submerged wood, 21 June 2002, L. Cai (HKUM 17146).

Notes

Dictyocheirospora tetraploides is morphologically similar to Di. musae in conidial shape, size, colour and appendages. However, conidia of Di. tetraploides have 5-rowed cells, while those of Di. musae are 7-rowed cells (Photita et al. 2002, Cai et al. 2003).

Dictyosporium species

Dictyosporium tubulatum J. Yang, K.D. Hyde & Z.Y. Liu, sp. nov.

Index Fungorum number: IF554771
Facesoffungi number: FoF04677
Figure 5

Etymology

Referring to the tubular conidial appendages.

Description

Saprobic on decaying plant substrates. Asexual morph: Colonies punctiform, sporodochial, scattered, dark brown to black, glistening. Mycelium mostly immersed, composed of smooth, septate, branched, hyaline to pale brown hyphae. Conidiophores micronematous, mononematous, septate, cylindrical, hyaline to pale brown, smooth-walled, 6.5–15 × 3.5–6 μm, sometimes reduced to conidiogenous cells. Conidiogenous cells monoblastic, integrated, terminal, determinate, hyaline to pale brown. Conidia acrogenous, solitary, cheiroid, smooth-walled, complanate, yellowish-brown to medium brown, mostly consisting of four arms closely compact with side arms lower than middle arms, rarely with five arms, 5–7-euseptate in each arm, guttulate, (22–)29–35(–38) × (14–)17–19(–22) μm (x¯ = 32.5 × 18 μm, n = 40), with hyaline, tubular, elongated appendages which are 19–24 × 3.5–7 μm and mostly attached at the apical part of two outer arms. Sexual morph: Undetermined.

Cultural characteristics

Conidia germinating on PDA within 24 h and germ tubes produced from the basal cell. Colonies on MEA reaching 5–10 mm diam. in a week at 25 °C, in natural light, circular, with fluffy, dense, white mycelium on the surface with entire margin; in reverse yellow in the middle and white at the margin.

Material examined

THAILAND. Prachuap Khiri Khan Province, near 12°30.19'N, 99°31.35'E, on decaying wood submerged in a freshwater stream, 25 December 2014, J. van Strien, Site 5-11-1 (MFLU 15-1166 holotype, HKAS 102136 isotype), ex-type living culture MFLUCC 15-0631; ibid. Trat Province, Amphoe Ko Chang, 12°08'N, 102°38'E, on decaying wood submerged in a freshwater stream, 27 April 2017, Y.Z. Lu, YJT 22-2 (MFLU 18-1044, HKAS 102137 paratype), living culture MFLUCC 17-2056.

Notes

Phylogenetic analyses showed that Dictyosporium tubulatum nested in Dictyosporium and sister to D. nigroapice. Dictyosporium tubulatum morphologically resembles D. alatum Emden, D. canisporum L. Cai & K.D. Hyde and D. thailandicum D’ souza, D.J. Bhat & K.D. Hyde in conidial ontogeny and conidial shape, colour and appendages. Dictyosporium tubulatum differs from the three species in the number of conidial cell rows. There are mostly four conidial columns in D. tubulatum while mostly five columns in the others. Dictyosporium tubulatum has smaller conidia (25–38 × 14–22 μm) than those in D. canisporum (32.5–47.5 × 20–25 μm) but has similar conidial size with D. alatum (26–32 × 15–24 μm) and D. thailandicum (15.4–34.5 × 14.5–20.6 μm) (Cai et al. 2003, Liu et al. 2015). Based on the molecular phylogeny, D. tubulatum is distinct from D. thailandicum and D. alatum. Unfortunately, molecular data are unavailable for D. canisporum.

Figure 5. 

Dictyosporium tubulatum (MFLU 15-1166, holotype). a, b Colonies on woody substrate c Squash mount of a sporodochium d–g Conidia h–i Conidia with conidiophores j–l Conidia with appendages m lateral view of a conidium n Germinated conidium o, p Culture, o from above p from reverse. Scale bars: a = 1000 μm, b = 200 μm, c, n = 30 μm, d, e = 10 μm, f–m = 15 μm.

Dictyosporium tratense J. Yang & K.D. Hyde, sp. nov.

Index Fungorum number: IF554772
Facesoffungi number: FoF04678
Figure 6

Etymology

Referring to the collecting site in Trat province, Thailand.

Description

Saprobic> on decaying plant substrates. Asexual morph: Colonies punctiform, sporodochial, scattered, black, glistening. Mycelium mostly immersed, composed of smooth, septate, branched, hyaline to pale brown hyphae. Conidiophores micronematous, mononematous, septate, cylindrical, hyaline to pale brown, smooth-walled, sometimes reduced to conidiogenous cells. Conidiogenous cells monoblastic, integrated, terminal, determinate, hyaline to pale brown. Conidia (40–)43–54(–57) × (20–)23–32(–36) μm (x¯ = 49.5 × 26 μm, n = 40), acrogenous, solitary, cheiroid, smooth-walled, complanate, yellowish-brown to light brown, consisting of 39–68 cells arranged in 4–6 (mostly 5) closely compact columns, 9–11-euseptate in each column, guttulate; the inner columns nested within the outer columns, the outer columns derived from the basal cell of the conidium; the intermediate columns are derived from the first or second cell of the outer columns; the inner columns derived from the first or second cell of the intermediate columns; usually with 2–3 central columns longest and of equal length, 2–3 peripheral columns shorter and of equal length; sometimes with hyaline globose appendages at the apical cells of outer columns with hyaline cloud-shaped mucilaginous sheath. Sexual morph: Undetermined.

Cultural characteristics

Conidia germinating on PDA within 24 h and germ tubes produced from basal cell. Colonies on MEA reaching 5–10 mm diam. in a week at 25 °C, in natural light, circular, with fluffy, dense, pale yellow mycelium in the middle and sparse mycelium in the outer ring on the surface with irregular margin; in reverse, dark yellow to brown in the middle and pale yellow at the margin.

Material examined

THAILAND. Trat Province, Amphoe Ko Chang, 12°08'N, 102°38'E, on decaying wood submerged in a freshwater stream, 27 April 2017, Y.Z. Lu, YJT 6-2 (MFLU 18-1042 holotype, HKAS 102133 isotype), ex-type living culture MFLUCC 17-2052 (Additional SSU sequence GenBank MH381761).

Notes

Phylogenetic analyses indicated Dictyosporium tratense nested within Dictyosporium and close to D. wuyiense. It is distinguished from the other species in the genus in having a mucilaginous sheath. Morphologically, D. tratense is most comparable to D. elegans in conidial colour and shape, but conidia of the new taxon (40-57 × 20-36 μm) are smaller than those of D. elegans (40-80 × 24-36 μm) (Goh et al. 1999).

Figure 6. 

Dictyosporium tratense (MFLU 18-1042, holotype). a Colonies on submerged wood b Squash mount of a sporodochium c Germinated conidium d–i Conidia j, k Culture j from above k from reverse. Scale bars: a = 200 μm, b = 50 μm, c = 30 μm, d–i = 20 μm.

Dictyosporium sp.

Figure 7

Material examined

THAILAND. Prachuap Khiri Khan Province, near 12°30.19'N, 99°31.35'E, on decaying wood submerged in a freshwater stream, 25 December 2014, J. van Strien, Site 5-5-1 (MFLU 15-1164), living culture MFLUCC 15-0629 (Additional SSU sequence GenBank MH381760).

Notes

Phylogenetic analyses indicated the isolate Dictyosporium sp. (MFLUCC 15-0629) was placed as sister taxon to D. digitatum (KH 401), D. aquaticum (MF 1318) and D. stellatum (CCFC 241241) with good support. The strain D. digitatum (KH 401), D. aquaticum (MF 1318) and our strain MFLUCC 15-0629, showed the same nucleotide (490 bp) between them for ITS gene regions, while there is only one nucleotide difference between our strain and D. stellatum (CCFC 241241). However, the strain Dictyosporium sp. (MFLUCC 15-0629) showed seven nucleotides different from D. digitatum (yone 280) for ITS gene regions. Morphologically, D. digitatum and D. aquaticum share the character in having appendages borne at the terminal cells of each conidial arm (Chen et al. 1991, Liu et al. 2015). Dictyosporium stellatum differs from D. digitatum and D. aquaticum in lacking conidial appendages (Crous et al. 2011). In this case, it is difficult to identify our collection based on the recommendations advocated by Jeewon and Hyde (2016) for differentiating species or establishing new species. Thus, we recommend designating this collection as unknown species until enough evidence is available for its identification.

Figure 7. 

Dictyosporium sp. (MFLU 15-1164). a Colonies on submerged wood b Squash mount of a sporodochium; c Germinated conidium b–e, h, i Conidia f Germinated conidium g Conidia with conidiophores j, k Culture, j from above, k from reverse. Scale bars: a = 200 μm, b, f–i = 30 μm, c = 50 μm d, e = 20 μm.

Dictyosporium nigroapice Goh, W.H. Ho & K.D. Hyde, Fungal Diversity 2: 83 (1999)

Index Fungorum number: IF450470
Facesoffungi number: FoF04683
Figure 8

Material examined

THAILAND. Trat Province, Amphoe Ko Chang, 12°08'N, 102°38'E, on decaying wood submerged in a freshwater stream, 27 April 2017, Y.Z. Lu, YJT 7-1 (MFLU 18-1043, HKAS 102134), living culture MFLUCC 17-2053 (Additional SSU sequence GenBank MH381762).

Notes

Conidia in Dictyosporium nigroapice are characterised by conspicuously darker apical cells of the two inner arms, rarely darker at the apex of the outer arms. Morphological characters of this collection well agree with the original diagnosis of the holotype of D. nigroapice (Goh et al. 1999).

Figure 8. 

Dictyosporium nigroapice (MFLU18-1043). a Colonies on submerged wood b, c Conidia and conidiophores d–j Conidia k Germinated conidium l, m Culture, l from above, m from reverse. Scale bars: a = 100 μm, b, c, j = 20 μm, d–i = 10 μm, k = 30 μm.

Discussion

Dictyosporiaceae accommodates a holomorphic group of Dothideomycetes, including 12 genera with nine being dictyosporous (Wijayawardene et al. 2017b, Wijayawardene et al. 2018). Dictyocheirospora and Dictyosporium are the two largest genera in the family. Dictyosporium has cheiroid, digitate and complanate conidia without separating arms, while Dictyocheirospora is characterised by non-complanate conidia with arms arising from the basal cell and closely gathered at the apex and compact. Thus, Dictyosporium hydei, D. indicum, D. musae and D. tetraploides are transferred to Dictyocheirospora based on the clear morphological characters. Phylogenetic analyses revealed the placement of Dictyocheirospora indica (MFLUCC 15-0056 reference specimen) within Dictyocheirospora. We believe that the other three species belong to Dictyocheirospora in having similar conidia and appendages to Dictyocheirospora indica, although molecular data are unavailable for them.

Acknowledgement

We would like to thank The Research of Featured Microbial Resources and Diversity Investigation in the Southwest Karst area (project no. 2014FY120100) for its financial support. Kevin D. Hyde would like to thank the Thailand Research grants entitled “The future of specialist fungi in a changing climate: baseline data for generalist and specialist fungi associated with ants, Rhododendron species and Dracaena species” (grant no: DBG6080013) and “Impact of climate change on fungal diversity and biogeography in the Greater Mekong Subregion” (grant no: RDG6130001) for supporting this study. Jing Yang thanks Shaun Pennycook for the corrections to the Latin names. Zong-Long Luo is acknowledged for the help with phylogenetic analyses.

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