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Research Article
Morphological and molecular identification of two new Ganoderma species on Casuarina equisetifolia from China
expand article infoJia-Hui Xing, Yi-Fei Sun, Yu-Li Han, Bao-Kai Cui, Yu-Cheng Dai
‡ Beijing Forestry University, Beijing, China
Open Access

Abstract

Ganoderma is a cosmopolitan white rot fungal genus, famous for its medicinal properties. In the present study, two new Ganoderma species were collected from south-eastern China and described on the basis of morphological characters and phylogenetic analyses of sequences of the internal transcribed spacer (ITS) region, the translation elongation factor 1-α gene (EF1-α) and the second subunit of RNA polymerase II (RPB2). Specimens of both species were found on living trees of Casuarina equisetifolia. Ganoderma angustisporum sp. nov. is characterised by its sessile basidiomata and almond-shaped, slightly truncate, narrow basidiospores (9–11.3 × 4–5.2 µm). Ganoderma casuarinicola sp. nov. is characterised by its strongly laccate reddish-brown pileal surface, luminous yellow to yellowish-brown cutis and ellipsoid, truncate basidiospores (9–10.2 × 5–6 µm). The two new species are compared with their related taxa. Phylogenetic analyses confirmed that G. angustisporum and G. casuarinicola are distinct species within Ganoderma.

Keywords

Ganodermataceae, medicinal mushroom, morphology, phylogeny, taxonomy, wood-rotting fungi

Introduction

Ganoderma P. Karst. is easily recognised by its characteristic appearance, double-walled and truncate basidiospores (Karsten 1881; Moncalvo and Ryvarden 1997). According to Christian (2015), there are 428 names in the Index Fungorum (http://www.indexfungorum.org/) and 456 records of taxa (420 with status legitimate) in MycoBank (http://www.mycobank.org/). Ganoderma products as dietary supplement are very popular in Asia, especially in China and China is very rich in Ganoderma species (Zhao and Zhang 2000; Wang et al. 2009; Cao et al. 2012; Cao and Yuan 2013; Li et al. 2014b). The great variability in macroscopic characters of basidiomes has resulted in a large number of synonyms and confusions in the taxonomy of this genus. Using DNA sequence data for the identification of Ganoderma species is of greatest importance.

Some Ganoderma species are well known for causing wood decay in a wide range of tree species around the world. For example, G. boninense Pat. is a causal agent of oil palm basal stem rot and is responsible for considerable yield losses in southeast Asian oil palm plantations (Pilotti 2005). Especially in Indonesia and Malaysia, G. boninense and G. philippii (Bres. & Henn. ex Sacc.) Bres. cause great economic loss of palm oil, tea and rubber (Zakaria et al. 2009).

Casuarina equisetifolia Forst. is used as an industrial raw material and wood fuel, as well as for conservation of coastal ecosystems and for agricultural land protection against salinity intrusion (Hossain et al. 1998; Chowdhury et al. 2009). In China, Casuarina equisetifolia is widely planted in the coastal areas of Guangxi, Guangdong, Fujian, Hainan and Taiwan provinces. During collections of wood-rotting fungi in South China in recent years, two Ganoderma species growing on Casuarina equisetifolia, which could not be identified to any known species, were collected. Those two species are here described based on morphological characters and phylogenetic analyses.

Materials and methods

Morphological studies

The examined specimens were deposited in the herbarium of the Institute of Microbiology, Beijing Forestry University (BJFC). Macro-morphological descriptions were based on field notes. Special colour terms followed Petersen (1996). Micro-morphological data were obtained from the dried specimens and observed under a light microscope following Li et al. (2014a) and Han et al. (2016). Sections were studied at a magnification of up to 1000× using a Nikon E 80i microscope and phase contrast illumination. Drawings were made with the aid of a drawing tube. Microscopic features, measurements and drawings were made from slide preparations stained with Cotton Blue and Melzer’s reagent. Spores were measured from sections cut from the tubes. To represent variation in the size of basidiospores, 5% of measurements were excluded from each end of the range and extreme values are given in parentheses.

The following abbreviations are used: IKI = Melzer’s reagent, IKI– = neither amyloid nor dextrinoid, KOH = 5% potassium hydroxide, CB = Cotton Blue, CB+ = cyanophilous, Q is an average computed by dividing the length by the width of each spore separately, n (a,b) = a spores measured from b specimens.

Molecular study and phylogenetic analysis

The CTAB rapid plant genome extraction kit-DN14 (Aidlab Biotechnologies Co. Ltd., Beijing, China) was used to extract total genomic DNA from dried specimens according to the manufacturer’s instructions with some modifications (Chen et al. 2016, 2017). The genes ITS, EF1-α and RPB2 were amplified by polymerase chain reaction (PCR) technique. The ITS region was amplified with primer pair ITS5 (GGA AGT AAA AGT CGT AAC AAG G) and ITS4 (TCC TCC GCT TAT TGA TAT GC) (White et al. 1990). Part of the EF1-α gene was amplified with primer pair EF1-983F (GCY CCY GGH CAY CGT GAY TTY AT) and EF1-1567R (ACH GTR CCR ATA CCA CCR ATC TT) (Rehner and Buckley 2005). Part of the RPB2 gene was amplified with primer pairs 5F (GAY GAY MGW GAT CAY TTY GG) and 7CR (CCC ATR GCT TGY TTR CCC AT) (Liu et al. 1999). The PCR cycling for ITS was as follows: initial denaturation at 95 °C for 3 min, followed by 35 cycles at 94 °C for 40 s, 54 °C for 45 s and 72 °C for 1 min and a final extension of 72 °C for 10 min. The PCR cycling for EF1-α was as follows: initial denaturation at 95 °C for 3 min, followed by 34 cycles at 94 °C for 40 s, 56 °C for 45 s and 72 °C for 1 min and a final extension of 72 °C for 10 min. The PCR cycling for RPB2 was as follows: initial denaturation at 95 °C for 5 min, followed by 35 cycles at 95 °C for 1 min, 58 °C for 2 min and 72 °C for 1.5 min and a final extension of 72 °C for 10 min. The PCR products were purified and sequenced at Beijing Genomics Institute (China), using forward and reverse PCR primers. All newly generated sequences were deposited in GenBank (Table 1).

Species, specimens, geographic origin and GenBank accession numbers of sequences used in this study.

Species name Voucher no. Geographic origin GenBank accession numbers References
ITS EF1-α RPB2
Ganoderma angustisporum Cui 13817 (holotype) Fujian, China MG279170* MG367563* MG367507* this study
G. angustisporum Cui 14578 Guangdong, China MG279171* MG367564* this study
G. angustisporum Cui 16340 Guangxi, China MG279172* this study
G. aridicola Dai 12588 (holotype) Durban, South Africa KU572491 KU572502 Xing et al. 2016
G. boninense WD 2028 Japan KJ143905 KJ143924 KJ143964 Zhou et al. 2014
G. boninense WD 2085 Japan KJ143906 KJ143925 KJ143965 Zhou et al. 2014
G. casuarinicola Dai 16336 (holotype) Guangdong, China MG279173* MG367565* MG367508* this study
G. casuarinicola Dai 16337 Guangdong, China MG279174* MG367566* MG367509* this study
G. casuarinicola Dai 16338 Guangdong, China MG279175* MG367567* MG367510* this study
G. casuarinicola Dai 16339 Guangdong, China MG279176* MG367568* MG367511* this study
G. curtisii CBS 100131 NC, USA JQ781848 KJ143926 KJ143966 Zhou et al. 2014
G. curtisii CBS 100132 NC, USA JQ781849 KJ143927 KJ143967 Zhou et al. 2014
G. destructans CBS 139793 (type) Pretoria, South Africa NR132919 Coetzee et al. 2015
G. destructans CMW 43670 Pretoria, South Africa KR183856 Coetzee et al. 2015
G. destructans Dai 16431 South Africa MG279177* MG367569* MG367512* this study
G. enigmaticum CBS 139792 (type) Pretoria, South Africa NR132918 Coetzee et al. 2015
G. enigmaticum Dai 15970 Africa KU572486 KU572496 MG367513* Xing et al. 2016; this study
G. enigmaticum Dai 15971 Africa KU572487 KU572497 MG367514* Xing et al. 2016; this study
G. heohnelianum Dai 11995 Yunnan, China KU219988 MG367550* MG367497* Song et al. 2016b; this study
G. heohnelianum Yuan 6337 Guangxi, China MG279160* MG367551* MG367498* this study
G. heohnelianum Cui 13982 Guangxi, China MG279178* MG367570* MG367515* this study
G. leucocontextum GDGM 44489 Xizang, China KM396271 Li et al. 2014b
G. leucocontextum GDGM 44490 Xizang, China KM396272 Li et al. 2014b
G. leucocontextum Dai 15601 Xizang, China KU572485 KU572495 MG367516* Xing et al. 2016; this study
G. lingzhi Wu 1006-38 (holotype) Hubei, China JQ781858 JX029976 JX029980 Cao et al. 2012
G. lingzhi Cui 14342 Sichuan, China MG279179* MG367571* MG367517* this study
G. lingzhi Cui 14375 Sichuan, China MG279180* MG367572* MG367518* this study
G. lobatum JV 1008/31 USA KF605671 MG367553* MG367499* this study
G. lobatum JV 1008/32 USA KF605670 MG367554* MG367500* this study
G. lucidum K 175217 UK, Europe KJ143911 KJ143929 KJ143971 Zhou et al. 2014
G. lucidum Cui 14404 Sichuan, China MG279181* MG367573* MG367519* this study
G. lucidum Cui 14405 Sichuan, China MG279182* MG367574* MG367520* this study
G. martinicense LIP SW-Mart08-44 Martinica KF963257 Welti and Courtecuisse 2010
G. martinicense LIP SW-Mart08-55 (type) Martinica KF963256 Welti and Courtecuisse 2010
G. martinicense He 2240 USA MG279163* MG367557* MG367503* this study
G. multipileum CWN 04670 Taiwan, China KJ143913 KJ143931 KJ143972 Zhou et al. 2014
G. multipileum Dai 9447 Hainan, China KJ143914 KJ143973 Zhou et al. 2014
G. multipileum Cui 14373 Sichuan, China MG279184* MG367575* MG367521* this study
G. multiplicatum SPC9 Brazil KU569553 Bolaños et al. 2016
G. multiplicatum 60119011 Brazil MG279185* this study
G. multiplicatum URM 83346 Brazil JX310823 Bolaños et al. 2016
G. orbiforme Cui 13918 Hainan, China MG279186* MG367576* MG367522* this study
G. orbiforme Cui 13880 Hainan, China MG279187* MG367577* MG367523* this study
G. philippii Cui 14443 Hainan, China MG279188* MG367578* MG367524* this study
G. philippii Cui 14444 Hainan, China MG279189* MG367579* MG367525* this study
G. resinaceum Rivoire 4150 France, Europe KJ143915 Zhou et al. 2014
G. resinaceum CBS 194.76 Netherlands, Europe KJ143916 KJ143934 Zhou et al. 2014
G. ryvardenii HKAS 58053 (type) Cameroon, Africa HM138671 Kinge and Mih 2011
G. ryvardenii HKAS 58054 Cameroon, Africa HM138672 Kinge and Mih 2011
G. ryvardenii HKAS 58055 Cameroon, Africa HM138670 Kinge and Mih 2011
G. shandongense Dai 15785 Shandong, China MG279190* MG367580* MG367526* this study
G. shandongense Dai 15787 Shandong, China MG279191* MG367581* MG367527* this study
G. shandongense Dai 15791 Shandong, China MG279192* MG367582* MG367528* this study
G. sinense Wei 5327 Hainan, China KF494998 KF494976 MG367529* this study
G. sinense Cui 13835 Hainan, China MG279193* MG367583* MG367530* this study
G. tropicum He 1232 Guangxi, China KF495000 MG367584* MG367531* this study
G. tropicum Yuan 3490 Yunnan, China JQ781880 KJ143938 Cao et al. 2012
G. tropicum Dai 16434 Hainan, China MG279194* MG367585* MG367532* this study
G. tsugae Dai 12751b CT, USA KJ143919 KJ143939 KJ143977 Zhou et al. 2014
G. tsugae Cui 14110 Jilin, China MG279195* MG367586* MG367533* this study
G. tsugae Cui 14112 Jilin, China MG279196* MG367587* MG367534* this study
G. weberianum CBS 219.36 Philippines JQ520219 Zhou et al. 2014
G. williamsianum Wei 5032 Hainan, China KU219994 Song et al. 2016b
G. williamsianum Dai 16809 Thailand MG279183* MG367588* MG367535* this study
G. zonatum FL-02 FL, USA KJ143921 KJ143941 KJ143979 Zhou et al. 2014
G. zonatum FL-03 FL, USA KJ143922 KJ143942 KJ143980 Zhou et al. 2014
Outgroup
Amauroderma rugosum Cui 9011 Guangdong, China KJ531664 KU572504 MG367506* Li and Yuan 2015; this study
Tomophagus colossus TC-02 Vietnam KJ143923 KJ143943 Zhou et al. 2014

Besides the sequences generated from this study, other reference sequences were selected from GenBank for phylogenetic analyses. 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). Sequence alignment was deposited in TreeBase (http://purl.org/phylo/treebase/phylows/study/TB2:S22403; submission ID 22403). Amauroderma rugosum (Blume & T. Nees) Torrend and Tomophagus colossus (Fr.) C.F. Baker were selected as outgroups.

Phylogenetic analyses in this study followed the approach of Song et al. (2016a) and Song and Cui (2017). The maximum likelihood (ML) and Bayesian inference (BI) methods were used to analyse the combined dataset of ITS, EF1-α and RPB2 sequences. ML analysis was conducted with RAxML-HPC252 on the Cipres Science Gateway (Miller and Pfeiffer 2011) involved 100 ML searches; all model parameters were estimated by the programme. The ML bootstrap values (ML-BS) were obtained with 1000 rapid bootstrapping replicates. BI was performed with MrBayes 3.1.2 (Ronquist and Huelsenbeck 2003), with a mixed model partition. A suitable substitution model for each partition of the dataset was determined using the Akaike Information Criterion implemented in MrMODELTEST 2.3. Four Markov chains were run from the random starting tree for 1 million generations to make the average standard deviation of split deviation frequencies lower than 0.01. Trees were sampled every 100 generations. The burn-in was set to discard the first 25% of the trees. A majority rule consensus tree of all the remaining trees was used to calculate Bayesian posterior probabilities (BPP). The ML and BI algorithms generated congruent topologies in main lineages; thus, only the topology from the ML algorithm was presented along with BS and BPP greater than 75% and 0.95, respectively, at the nodes.

Results

Phylogenetic analysis

The combined ITS, EF1-α and RPB2 dataset included sequences from 66 fungal samples representing 27 taxa. The selected models were K80 for 5.8S, K80 + G for ITS1, HKY + G for ITS2, GTR + I + G for ITS1+ ITS2 + 5.8S. The best model selected and applied in the BI analysis for the combined ITS, EF1-α and RPB2 partition was a GTR+I+G model. BI analysis and ML analysis resulted in the same topology with an average standard deviation of split frequencies = 0.006025 (BI).

Taxonomy

Ganoderma angustisporum J.H. Xing, B.K. Cui & Y.C. Dai, sp. nov.

MycoBank No: MB823320
Figs 2a–b, 3

Diagnosis

Ganoderma angustisporum is characterised by its sessile basidiomata, white pore surface, almond-shaped, slightly truncate and narrow basidiospores.

Holotype

CHINA. Fujian Prov., Pingtan County, on living tree of Casuarina equisetifolia, 18 August 2016, Cui 13817 (BJFC!).

Etymology

angustisporum (Lat.): referring to the narrow basidiospores.

Description

Basidiomes annual, sessile and broadly attached, applanate, shell-shaped, projecting up to 13.5 cm, 10 cm wide and 1.1 cm thick at base, corky when fresh, becoming hard corky to woody hard upon drying. Pileal surface strongly laccate, reddish-brown to dark brown, with a thin crust, concentrically zonate or azonate; margin distinct, slightly obtuse. Pore surface white when fresh, turning light buff when dry; pores round to angular, 3–5 per mm; dissepiments slightly thick to thick, entire. Context corky, homogeneous, greyish-brown, bearing distinct concentric growth zones, black melanoid band present, up to 0.4 cm thick. Tubes woody hard, greyish-brown, up to 0.7 cm long. Hyphal system trimitic; generative hyphae bearing clamp connections; all the hyphae IKI–, CB+; tissues darkening in KOH. Pellis: pellis cells regularly arranged into a palisade; terminal cells clavate, yellowish to pale brown, thin-walled, occasionally with blunt outgrowth and protuberance in the apical or lateral parts, bearing a simple septum at base, moderately amyloid at maturity, 15–33 × 4–10 μm. Context generative hyphae colourless, thin-walled, bearing clamp connections, unbranched, 2–4.5 µm in diam; skeletal hyphae dominant, pale yellowish-brown, thick-walled to subsolid, frequently branched, interwoven, 3–6 µm in diam; binding hyphae abundant, pale yellowish-brown, thick-walled with a narrow lumen to subsolid, frequently branched, tortuous, interwoven, 1–2.5 µm in diam. Tubes generative hyphae colourless, thin-walled, bearing clamp connections, unbranched, slightly swollen at the distal end, 2–2.8 μm in diam; skeletal hyphae dominant, pale brown to distinctly brown, thick-walled with a medium or narrow lumen to subsolid, frequently branched, strongly interwoven, 3–4.5 μm in diam; binding hyphae brownish-yellow, thick-walled to almost solid, frequently branched, interwoven, 1–1.8 μm in diam. Basidia barrel-shaped, yellowish to pale brown, with a clamp connection and four sterigmata, 11–16 × 6.5–9 µm; basidioles pear-shaped to fusiform, 8–15 × 5–8 µm. Basidiospores mostly almond-shaped at maturity, slightly truncate, yellowish to pale brown, IKI–, CB+, double-walled, exospore smooth, endospore with coarse echinulate, (8–)9–10.5(–11) × (3.5–)4–5 µm, L = 8.89 μm, W = 4.27 μm, Q = 2.01–2.24 (n = 60/2, with the turgid vesicular appendix excluded); (8–)9–11.3(–12) × (3.8–)4–5.2 µm, L = 10.26 μm, W = 4.31 μm, Q = 2.36–2.4 (n = 60/2, with the turgid vesicular appendix included).

Figure 1. 

Phylogeny of the new Ganoderma species and related taxa based on ITS+EF1-α+RPB2 sequence data. Branches are labelled with bootstrap values (ML) higher than 75%, and posterior probabilities (BI) higher than 0.95. Bold names = new species.

Figure 2. 

Basidiomata of Ganoderma species. a, b G. angustisporum (Cui 13817) c, d G. casuarinicola (Dai 16336). Scale bars: 2 cm.

Figure 3. 

Microscopic structures of Ganoderma angustisporum (drawn from the holotype). a Basidiospores b Apical cells from the pellis c Basidia and basidioles d Hyphae from context e Hyphae from trama. Scale bars: 10 µm.

Figure 4. 

Microscopic structures of Ganoderma casuarinicola (drawn from the holotype). a Basidiospores b Apical cells from the cuticle c Basidia and basidioles d Hyphae from context e Hyphae from trama. Scale bars: 10 µm.

Type of rot

A white rot.

Additional specimens examined

CHINA. Guangdong Prov., Maoming, Dianbai, on living trees of Casuarina equisetifolia, 20 June 2017, Cui 14578, Cui 16494 and Cui 16495 (BJFC!).

Ganoderma casuarinicola J.H. Xing, B.K. Cui & Y.C. Dai, sp. nov.

MycoBank No: MB823321
Figs 2c–d, 4

Diagnosis

Ganoderma casuarinicola is characterised by its strongly laccate reddish-brown pileal surface, white pore surface, luminous yellow to yellowish-brown cutis.

Holotype

CHINA. Guangdong Prov. Zhanjiang, Dianbai, on living tree of Casuarina equisetifolia, 4 October 2015, Dai 16336 (BJFC!).

Etymology

casuarinicola (Lat.): referring to the host tree genus Casuarina.

Description

Basidiomes annual, stipitate to substipitate, pileus sectorial to shell-shaped, projecting up to 10 cm, 7 cm wide and 2 cm thick at base, corky, without odour when fresh, becoming hard corky to woody hard when dry. Pileal surface strongly laccate, reddish-brown, with a thin crust; margin obtuse, cream to reddish-brown. Stipe flattened or subcylindrical, lateral, reddish-brown, up to 6 cm long and 1.7 cm in diam. Pore surface white when fresh, turning cream when dry; pores round to angular, 4–6 per mm; dissepiments thin to slightly thick, entire. Context corky, heterogeneous, the upper layer generally light yellow up to 0.1 cm thick and the lower layer generally dark brown close to the tubes up to 1 cm thick, showing distinct concentric growth zones, black melanoid band absent. Tubes woody hard, greyish-brown, up to 0.9 cm long. Hyphal system trimitic; generative hyphae bearing clamp connections, occasionally with simple septa; all the hyphae IKI–, CB+; tissues darkening in KOH. Pellis: Pellis cells regularly arranged into a palisade; terminal cells clavate, luminous yellow to yellowish-brown, thick-walled, occasionally expanded at the apex, moderately amyloid at maturity, 40–70 × 5–13 μm. Context generative hyphae colourless, thin-walled, with clamp connections, occasionally branched, 2–4 µm in diam; skeletal hyphae dominant, pale yellowish-brown, thick-walled to subsolid, frequently branched, interwoven, 3–5.5 µm in diam; binding hyphae abundant, pale yellowish-brown, thick-walled with a narrow lumen to subsolid, frequently branched, tortuous, interwoven, 1–3 µm in diam. Tubes generative hyphae colourless, thin-walled, mostly bearing clamp connections, occasionally with simple septa, occasionally branched, slightly swollen at the distal end, 1.5–3 μm in diam; skeletal hyphae dominant, pale brown to distinctly brown, thick-walled with a medium or narrow lumen to subsolid, frequently branched, strongly interwoven, 2–4.5 μm in diam; binding hyphae brownish-yellow, thick-walled to almost solid, frequently branched, interwoven, 1.5–2.5 μm in diam. Basidia barrel-shaped, yellowish to pale brown, with a clamp connection and four sterigmata, 12–18 × 9.5–13 µm; basidioles pear-shaped, 9–16 × 8–12 µm. Basidiospores mostly ellipsoid at maturity, truncate, yellowish to pale brown, IKI–, CB+, double-walled, exospore smooth, endospore with coarse echinulate, (8–)8.5–9 (–10) × (4.2–)5.5–6.5(–7) µm, L = 8.82 μm, W = 5.65 μm, Q = 1.52–1.60 (n = 60/2, with the turgid vesicular appendix excluded); (8.3–)9–10.2(–11.5) × (4.5–)5–6(–7) µm, L = 9.85 μm, W = 5.77 μm, Q = 1.68–1.72 (n = 60/2, with the turgid vesicular appendix included).

Type of rot

a white rot.

Additional specimens examined

CHINA. Guangdong Prov., Zhanjiang, Dianbai, on living trees of Casuarina equisetifolia, 4 October 2015, Dai 16337, Dai 16338, Dai 16339, Dai 17892, Cui 16370, Cui 16376 and Cui 16377 (BJFC!).

Discussion

The two new Ganoderma species were found on living trees of Casuarina equisetifolia from the southeast coast of China. However, they are quite different from each other in morphology. Their main morphological differences are presented in Table 2. Phylogenetically, the two new species grouped together with some other laccate Ganoderma species in a well-supported clade.

Morphological differences between the two new Ganoderma species collected on Casuarina from China.

Species Pileal surface Context Cuticle cells Shape of basidiospores Size of basidiospores
G. angustisporum reddish brown to dark brown homogeneous, black melanoid band present thin-walled, septate almond-shaped (8–)9–10.5(–11) × (3.5–)4–5 µm (with the turgid vesicular appendix excluded) (8–)9–11.3(–12) × (3.8–)4–5.2 µm (with the turgid vesicular appendix included)
G. casuarinicola reddish brown not fully homogeneous, black melanoid band absent thick-walled to subsolid, non-septate ellipsoid (8–)8.5–9 (–10) × (4.2–)5.5–6.5(–7) µm (with the turgid vesicular appendix excluded)(8.3–)9–10.2(–11.5) × (4.5–)5–6(–7) µm (with the turgid vesicular appendix included)

In the phylogenetic tree inferred from ITS, EF1-α and RPB2 sequences, G. angustisporum clustered together with G. boninense, G. ryvardenii Tonjock & Mih and G. zonatum Murrill, these four species forming a strong support (BS = 100%, BPP =1.00; Fig. 1) lineage and could be distinctly separated from each other in the tree. Morphologically, all these four species produce laccate and sessile basidiomata, but G. angustisporum has the narrowest basidiospores amongst so far accepted Ganoderma species. Ganoderma boninense is another species producing relatively narrow basidiospores, but its basidiospores (8.7–12.8 × 4.7–6 μm, Zhou et al. 2014) are slightly wider than G. angustisporum. Moreover, its pileal surface ranges from orange to reddish-brown, even to fuscous or almost black and it lacks concentric growth zones in the context. Ganoderma ryvardenii differs from G. angustisporum by its larger pores (2–4 per mm), reddish basidiomata with waved margin and wider basidiospores (10–13 × 6–8 μm; Kinge and Mih 2011). Ganoderma zonatum mainly differs by larger basidiospores (10–12 × 5.3–6.3 μm, Zhou et al. 2014) and the absence of black melanoid band in the context.

In the phylogenetic tree, we obtained G. casuarinicola as sister to G. enigmaticum M.P.A. Coetzee, Marinc. & M.J. Wingf., a species described from South Africa, but morphologically, G. enigmaticum can be easily distinguished from G. casuarinicola by its golden yellow pileal surface without furrows and narrower basidiospores (8–11 × 3.5–6 μm, Coetzee et al. 2015). These two species gathered together with another South Africa species G. aridicola J.H. Xing & B.K. Cui, but G. aridicola is a sessile species with dark brown to black pileal surface, while G. casuarinicola has a reddish-brown pileal surface. Besides, G. casuarinicola has smaller basidia than G. aridicola (15–25 × 8–11 μm, Xing et al. 2016). Morphologically, G. casuarinicola resembles G. tsugae Murrill in having a reddish-brown pileal surface, white pore surface, similar wide ellipsoid basidiospores and lacking the black melanoid band in the context, but G. tsugae mainly differs by the absence of a light yellow layer under the laccate crust and concentric growth zones in the context (Zhou et al. 2014) and they are distinct from each other in the phylogenetic tree (Fig. 1). Besides, G. tsugae grows exclusively on conifers, especially on Tsuga, Abies and Larix, while G. casuarinicola occurs on hardwoods.

In conclusion, both morphology and phylogeny inferred from the combined ITS, EF1-α and RPB2 sequences support that the specimens, collected on living trees of Casuarina equisetifolia from the southeast coast of China, are two new species within the Ganoderma genus.

Acknowledgments

The research was financed by the National Natural Science Foundation of China (Project No. 31670016) and the Fundamental Research Funds for the Central Universities (Project No. 2016ZCQ04).

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