Armillaria

Armillaria (Fr.) Staude, Schwämme Mitteldeutschl. 28: xxviii, 130 (1857)

Background

Armillaria is a plant pathogenic genus in the phylum Basidiomycota, family Physalacriaceae (He et al. 2019), collectively referred to as shoestring root-rot fungi or honey mushrooms. Armillaria can cause root-rot disease in a wide variety of woody hosts worldwide. Armillaria has undergone significant revision in the past 20 years. The genus once accommodated any white-spored agaric with broadly attached gills and an annulus (Volk et al. 1996). Armillaria mellea is the type species. Most Armillaria species have the potential to infect healthy and stressed trees, they differ in their pathogenicity to their hosts and under certain circumstances, they behave as obligate saprobes. Most Armillaria species are facultative necrotrophs causing root and butt rot on a broad range of woody plants affecting a variety of forest, shade, ornamental and orchard trees and shrubs. Some Armillaria species cause significant economic losses to forest trees and in nursery plantations. Armillaria root disease is found in many temperate and tropical forests throughout the world. This fungus spreads mainly through the interaction of tree roots. As saprotrophs, Armillaria species are important wood decomposers that contribute to nutrient cycling in forest ecosystems. As pathogens, they infect and eventually kill susceptible trees, which impacts forest structure, composition and succession. Trees that are used for fibre or lumber production, as well as trees located in recreation sites, are affected by these diseases. Such Armillaria infections may cause yield reduction and tree mortality in silvicultural and agricultural tree plantations and provoke economic losses.

Armillaria species are expected to become more aggressive during drought and thus enhance root rot (La Porta et al. 2008; Kolb et al. 2016; Kubiak et al. 2017). The incidence of Armillaria related root disease is likely to increase as temperatures increase and precipitation decreases due to climate change (Sturrock et al. 2011). Whilst the ability of the pathogen to sporulate, spread and infect is affected by temperature and moisture, factors that stress host trees directly may be just as critical to a successful invasion of host tissues. It seems likely that the disease will become more severe in the future, wherever Armillaria susceptible tree species are subjected to increased levels of climate stress (Klopfenstein et al. 2009). Currently, Armillaria root disease causes large growth/volume losses (e.g., 16–55%) in areas of western and North America (Filip and Goheen 1984; Cruickshank Morrison et al. 2011; Lockman and Kearns 2016). Armillaria root disease is typically more severe in trees that are maladapted to climate-induced stress (Ayres and Lombardero 2000; Kliejunas et al. 2009; Sturrock et al. 2011). Thus, it is likely that climate change will further exacerbate damage from Armillaria root disease, which can further predispose trees to beetle attack (e.g. Hertert et al. 1975; Tkacz and Schmitz 1986; Goheen and Hansen 1993).

Armillaria mellea is an edible species that has long been used as a Traditional Chinese Medicine. Some of Armillaria species are is believed to be able to improve health and prevent various diseases, such as insomnia, pain, and neurasthenia. Extracts of A. mellea exhibit anti-oxidative, anti-inflammatory and immune-modulatory activities. Armillaria mellea can also induce maturation of human dendritic cells. The chemical constituents isolated from A. mellea include sesquiterpenoids, steroids, triterpenoids, adenosine and resin acids. Armillariol C is a furan-based natural product isolated from Armillaria species. A xylosyl 1,3-galactofucan (AMPS-III) was isolated and identified as a novel anti-inflammatory agent from this species.

Classification Basidiomycota, Agaricomycotina, Agaricomycetes, Agaricomycetidae, Agaricales, Physalacriaceae (He et al. 2019)

Type species Armillaria mellea (Vahl) P. Kumm.

Distribution Worldwide, mostly in temperate areas (northern and southern hemisphere) and some in tropical areas.

Disease symptoms Armillaria root disease, shoestring root rot

Symptoms caused by this fungus can be categorized into two categories:

Crown symptomsbranch dieback, crown thinning, chlorosis, reddening of foliage or heavier than normal production of cones.

Basal symptoms the fungus can grow up from the roots in the inner bark in some tree species and causes basal cankers above the infected roots. Resinosis (exudation of resin) can be observed in resinous conifers. In some plants, decayed roots or decay in the inner wood of stem bases can be observed. Species cause a white rot of wood. In white rot, wood often has a bleached, whitish appearance and are spongy or stringy, and maybe wet. Black lines called “zone lines” are usually seen in the decayed wood. These lines are curved planes in the wood, sometimes called “pseudosclerotial plates”, composed of thickened, dark fungal cells. They may play a role in the protection of Armillaria from unfavourable conditions or other fungi that attempt to invade its territory, including other individuals of the same species. Actively decaying wood may be luminescent, producing a faint glow in the dark (Baumgartner et al. 2002; Worrall 2004; Klopfenstein 2009).

There are three major signs of Armillaria root disease in the field.

Mycelial fans can always be seen in infected and recently killed trees. These are white mats of fungal mycelium between the inner bark and wood that are generally substantial and have a mushroom odour.

Rhizomorphs are commonly associated with infection and are often attached to infected roots, but they may also be attached to the surface of uninfected roots. Depending on the species these may be few, small, fragile, hard to find or abundant and robust. Rhizomorphs can be cylindrical in soil or flattened under bark, reddish-brown to black branched and have a cream-coloured tip when actively growing (Guillaumin and Legrand 2013).

Mushrooms that have honey-brown caps can be seen in clusters near or on the base of trees.

Hosts Many angiosperms and gymnosperms (especially conifers) in native, planted forests, orchards and vineyards (Farr and Rossman 2020).

Pathogen biology, disease cycle and epidemiology

Sexual reproduction results in the diploid mycelium. Such a mycelium is the dominant phase that is found growing in wood, growing through the soil as rhizomorphs, and killing trees. Armillaria species can be dispersed through airborne sexual basidiospores which will establish a new infection center. These taxa do not reproduce asexually but disperse by growing mycelium which is the most common source of infection, through root contacts or root grafts or by growing through the soil as rhizomorphs. Mycelium in colonized roots and the rhizomorphs produced serve as the most common mode of infection and may survive for up to 50 years or more in stumps, depending on the climate, size of the stump, and other factors (Baumgartner et al. 2002; Worrall 2004; Klopfenstein 2009).

 

Morphology-based identification and diversity

Armillaria has included only white-spored wood-inhabiting agarics with broadly attached to decurrent gills and macroscopic black to reddish-brown rhizomorphs. Armillaria basidiomes are easily recognized by their caespitose habit, annulus and honey colour. It is, however, extremely difficult to identify some species due to the lack of morphological apomorphies (Watling et al. 1991; Pegler 2000). Besides, basidiomata are often not available to differentiate species, which further complicates the taxonomy of Armillaria (Harrington and Wingfield 1995). In this regard, Armillaria provides a clear example of where a phylogenetic approach can contribute significantly to its taxonomy. Until the late 1970s, Armillaria mellea was considered by most researchers to be a polymorphic species with a wide host range and distribution. Herink (1973), among others, suspected that this single species might be a species complex. However, since the morphology of basidiomata is difficult to study because of overlapping and inconsistent traditionally used morphological characters, other avenues of research were pursued. Hintikka (1973) developed a technique that allowed the determination of mating types in Armillaria. Using a modification of this method, Korhonen (1978a) was able to distinguish five European biological species. The cumbersome nature of the mating-type method of species identification prompted a search for other techniques for identifying collections. They were able to separate all North American species (NABS) of Armillaria except for A. calvescens and A. gallica, which are apparently very closely related (Anderson and Stasovski1992). Ten species of Armillaria in North America have been confirmed from multiple studies utilizing a combination of morphological, biological and phylogenetic species concepts (Anderson and Ullrich 1979; Anderson and Stasovski 1992; Burdsall and Volk 1993; Kim et al. 2006; Ross-Davis et al. 2012). Before, A. mellea shows great variability in morphology and hosts. These species were first separated using interfertility tests using cultures of Armillaria haploid tester strains and morphology. Now, A. mellea is considered as an independent species, with two North American biological species (Bérubé and Dessureault 1989; Volk et al. 1996).

Fig. 1 Disease cycle of Armillaria mellea (redrawn from Agrios 2005)

Molecular-based identification and diversity

Problems surrounding the identification of Armillaria have led to important advances in developing robust but rapid DNA techniques. Such techniques have initially included DNA-base composition (Jahnke et al. 1987) DNA-DNA hybridization (Miller et al. 1994), sequence analyses of the IGS-1(Anderson and Stasovski 1992) and ITS (Coetzee et al. 2001a,b), RFLPs without PCR (Smith and Anderson 1989) and RFLPs of IGS-1 amplicons (Harrington and Wingfield 1995). Although several of these techniques might pose some problems (Pérez‐Sierra et al. 2000), by their relative simplicity they have gradually replaced traditional, morphological methods.

The amount of DNA sequence data on Armillaria species has increased substantially since the first publication on the phylogeny of the genus in the northern hemisphere (Anderson and Stasovski 1992). As with many other fungal genera, the focus of such studies initially was set on species of Europe and North America (Chillali et al. 1998; Coetzee et al. 2000b). Later, substantial datasets for species in Africa, Australasia and southeast Asia have become available (Terashima et al. 1998; Coetzee et al 2000a; 2001a). At present, ITS, IGS-1 and tef1 sequences are available in GenBank for the best-known species of Armillaria. However, there are disjunctions in data sets and relatively little is known about species from Indo-Malaysia and South America. Armillaria fruiting bodies are produced seasonally and not every year; they are, therefore, often not available during fieldwork (Kile et al. 1991).

Identification using the biological species concept with species identification based on sexual compatibility tests (Korhonen 1978a) has been examined for its utility by some mycologists, but its application was soon abandoned. This was because of complications due to the absence of known tester strains, lack of haploid strains, ambiguous mating interactions and degeneracy of cultures. For these reasons, DNA-based molecular techniques have finally been preferred in Armillaria taxonomy, either complementing other methods or on their own. The techniques utilized for the taxonomy of Armillaria species include comparisons of RFLPs (Harrington and Wingfield 1995), AFLPs (Pérez-Sierra et al. 2004), and the use of sequences from the ITS, IGS-1 and tef1 gene in phylogenetic studies (Coetzee et al. 2000b, 2001a; Maphosa et al. 2006; Kim et al. 2006). Phylogenetic methods have made it possible to differentiate the lineages of the genus in southern Argentina (Pildain et al. 2009). Lineages I and II grouped with A. novae-zelandiae and A. luteobubalina, respectively, while Lineages III and IV represented unique taxa that were closely related to A. hinnulea, Armillaria 4th species from New Zealand (established by Coetzee et al. 2001) and Armillaria Group III from Kenya (Mwenje et al. 2006). Modern approaches to identification of Armillaria species are mostly based on the analyses of DNA sequences. The present study reconstructs the phylogeny of Armillaria based on a combined ITS, IGS and tef1 sequence data (Fig 2, Table 2). However, insufficient data are available for the LSU gene region in GenBank. Then, it is difficult to have comparative phylogenetic analyses but the single gene analysis of each gene was carried out to compare the topology of the tree and clade stability. This phylogenetic tree is largely in accordance with earlier studies from Coetzee et al. (2018) and provides the most conclusive phylogeny of the genera to date. Genealogical concordance phylogenetic species recognition (GCPSR) using the concordance among several gene trees (Taylor et al. 2000; Dettman et al. 2003) to delineate species has become standard in fungal taxonomy. However, except for a few studies (Guo et al. 2016; Tsykun et al. 2013), this taxonomic method has not been widely implemented in Armillaria taxonomy. Sequences of the genomes of key species are already providing prospects to study the evolution and systematics of Armillaria. They are certain to lead to important breakthroughs regarding not only the taxonomy but the biology and ecology of these fungi in the future (Sipos et al. 2017).

Recommended genetic marker (genus level)ITS

Recommended genetic markers (species level)ITS, IGS1, tef1

Additional genetic markers (species level)LSU, tub2

Accepted number of species There are 278 epithets in Index Fungorum (2020) listed for this genus. However, sequence data are only available for 31 species including 16 groups of unnamed species (Table 1).

References Watling et al. 1991, Pegler 2000, Harrington and Wingfield 1995 (morphology); Coetzee et al. 2000a,b, 2001a,b, Maphosa et al. 2006, Mwenje et al. 2006, Kim et al. 2006, Coetzee et al. 2018 (molecular phylogeny).

 

Table 1 DNA barcodes available for Armillaria. Ex-type/ex-epitype/ex-neotype/ex-lectotype strains are in bold and marked with an asterisk (*). Voucher strains are also in bold.

 

Species Sources Country ITS LSU tef1 IGS1
Armillaria affinis JMCR.126  Central America? AF261356
A. altimontana POR100* USA AY213579, AY213580 JN944606, JF313117 AY509181
A. aotearoa NZFRI-M 5283* New Zealand  NR_151846 KU295542
A. borealis CMW31075 Belarus KM205252 KM205305
CMW31072 China KM205251 KM205304
HKAS 76263, Gt571 China KT822294 KT822426
BRNM 699842, MUAF 501 Czech Republic EU257713 EU251402 EU257708
CMW3172 Finland DQ338540 DQ435623
A1 Finland JN657467 JN657494 JN657440
A5 Germany JN657468 JN657495 JN657441
A618 Switzerland JN657469 JN657496 JN657442
A. calvescens ST3 USA AY213559 JF895899 JF313138, JF895835 AY509163
ST17 USA AY213560, AY213561 JF895900 JF313130, JF895836 AY509164
TH DJA 91/PUL F2895 Cameroon KU170952 KU170942 KU289112
A. cepistipes BRNM 706814, MUAF 516 Czech Republic EU257715 EU251395 EU257709
M110 Canada AY213581 JF313121 AY509182
HKAS 86583, 01108/1 China KT822290 KT822417
B3 Finland JN657445 JN657472 JN657418
B5 Italy JN657446 JN657473 KJ414321 JN657419, KJ414318
94-39-04 Japan AB510853 AB510786 AB510809
SY1Ra UK? JF746917 JF288720
C5C-S1 Ukraine JN657450 JN657477 JN657423
W113 USA AY213583 JF313115 AY509184
BRNM 695717 Czech Republic EU257716 EU251396 EU257710
HKAS 86586, 97033/1 China KT822263 KT822416
KFRI1616 Korea MG543860 MG544785
A. ectypa BRNM 704974 Austria EU257720 EU251403 EU257712
CMW15693 France DQ338547 FJ875698
HKAS 86565, 70011/13 France KT822340 KT822438
TFM27105, Je-2 Japan AB559000 AB558992
A. fumosa CMW4957, 123 Australia AF329917 DQ338552 DQ435646
A. fuscipes CBS 118122, CMW5844, WG1I Ethiopia AY882969 AY172032
CMW7184 Kenya AY882973 AY882965
CMW4953 La Reunion AY882974 DQ338556 DQ435622 AY882963
CMW4871 Malawi AY882976 AY882959
CMW2717 South Africa AY882971 AF204821
CMW4949 Tanzania AY882978 AY882961
CMW4874 Zimbabwe AY882967 AF489481
A. gallica M70 Canada AY213568 JF313123 AY509171
CMW31087 China KM205260 KM205313
HKAS 86569, 93421/1 China KT822277 KT822414
BRNM 706835, MUAF 575 Czech Republic EU257718 EU251390 EU636240
E4 France JN657452 JN657479 JN657425
86-016/3 Germany KJ200952 KJ200946
86-008/2 Iran KJ200954 KJ200948
NA4 Japan AB510881 AB510761 AB510834
MEX55 Mexico JX281809 KC111014 JX281799
CMW7202 South Africa AY190247 AY190245
HY2a Ukraine  JN657455  JN657482  JN657428
Aga235 USA JF895911 JF895847
ST22, EL-1 USA AY213569, AY213570 JF895912 JF313126, JF895848 AY509172
Ame10 Korea MG543850 MG544774
KA14-1647 Korea MG543859 MG544784
Ame7 Korea MG543852 MG544777
A. gemina JB-38A Canada FJ664586 FJ618757 FJ618670
ST8 USA AY213555 JF313136 AY509158, AY509159
A. heimii C4 Congo AY333917 AY330630
166 AY333913 AY330634
K59 Kenya AY333916 AY330627
A. hinnulea CMW4980 Australia DQ338555 DQ435648 AF445077
CMW4990 New Zealand AF329905 DQ338555 DQ435648
A. jezoensis HUA9116 Japan D89921
A. limonea CMW4680 New Zealand AF329930 DQ338560 DQ435655 AF445073
A. lutea 90-4 (Alut) USA AF243066
A. luteobubalina CMW4977 Australia AF329912 DQ338559 DQ435657 AF445069
A. mellea AFTOL-ID449 USA AY789081 AY700194 AY881023
  B176 England AF163578 AF163602
HKAS 86590, 00020/6 China KT822251 KT822354
D1 France JN657464 JN657491 JN657437
B1212, CMW4615, 94056/1 Hungary AF163581 AF163605
B1205, CMW4613, 86009/1 Iran AF163583 DQ435637 AF163606
CBS122232, CMW11265, 426 Italy FJ875692 FJ875694 DQ435636
FFPRI420861, WD2588, 89-07 Japan AB510852 AB510796 AB510808
HKAS 86598, PFD84-103 Kenya KT822248 KT822348
MEX74 Mexico JX281807 KC111011 JX281797
CMW3975 South Africa AF310329 AF310327
B916, CMW4610, A-5 South Korea AF163592 DQ435639 AF163612
HY-3 Ukraine JN657466 JN657493 JN657439
Am115 USA JF895920 JF895856
B927 USA AF163595 FJ875695 DQ435634 AF163608
CMW31161 China KM205267 KM205320
CMW8082 Bhutan AY554333 AY554335
HUA93110 Japan D89922
A. mexicana MEX87* Mexico KR061310 KR061314 KR061306
A. montagnei (ex luteobublina) CMW5446 Argentina AF448422 DQ338562 DQ435650 AF445068
A. montagnei (ex luteobublina) CMW8876 Chile AF448423 DQ435658 AF445065
A. montagnei (Lineage II) Arg309 Argentina FJ660939 FJ711625
A. montagnei (Lineage II) Arg270* Argentina FJ711609
A. nabsnona ST16 USA AY213574 JF313124 AY509178
HKAS 85523, Gt798 China KT822333 KT822411
M90 Canada AY213573 JF313122 AY509176, AY509177
00-3-1 Japan AB510899 AB510766 AB510850
C21 USA AY213572 JF313119 AY509174, AY509175
CMW6905 USA DQ338542 DQ435631
Juk14411 Korea MG543857 MG544782
A. novae-zelandiae CMW4967 Australia AF329921 DQ435651
CMW5448 Chile AF448417 DQ338554 DQ435653
CMW4143 Indonesia AF448421 DQ338564 DQ435654
CMW3951 Malaysia AF448419 DQ338553
CMW4722 New Zealand AF329926 DQ338551 DQ435652
A. novae-zelandiae (Lineage I) Arg49 Argentina FJ660935 FJ711629
A. ostoyae SP308014* Brazil EF639348
  BRNM706815 Czech Republic EU257717 EU251400 EU257711
CMW31102 China KM205272 KM205325
HKAS 86579, 96043/11 China KT822310 KT822428
C2 France JN657459 JN657486 JN657432
88-01-19 Japan AB510859 AB510784 AB510815
D20 Switzerland JN657463 JN657490 JN657436
HpAg1 Ukraine JN657462 JN657489 JN657435
P1404 USA AY213554 JF313140 AY509157
Ame5 Korea MG543851 MG544776
3626 Australia FJ664607 FJ618752 FJ618665
A. puiggarii MCA 3111/PUL F2896/BRG 41295 Guyana KU170954 KU254228 KU289104
A. sinapina V48.5 Canada FJ664609 FJ618763 FJ618676
M50 Canada AY213563, AY213564 JF313114 AY509167
CMW31112 China KM205277 KM205330
HKAS 86566, 96015/39 China KT822323 KT822422
96-7-1 Japan AB510873 AB510774 AB510827
P2-7 USA JF895916 JF895850
ST12 USA AY213565 JF313132 AY509168
A. singula HUA9101* Japan D89926
A. socialis T2 France DQ784801
A. solidipes MS2-11 USA JF895918 JF895852
CMW31107 Finland KM205275 KM205328
A. sparrei PSpa86.5 Argentina FJ664612 FJ618750
Arg12 Argentina FJ660948 FJ711618
A. umbrinobrunnea Arg25 Argentina FJ660946 FJ711621
A. tabescens CMW31118 China KM205280 KM205333
99122/13 China KT822339 KT822441
CMW3165 France DQ338546 DQ435642
CMW31119 Italy KM205281 KM205334
HKAS 86604, CT1097.3 Italy KT822338 KT822440
96-1-8 Japan AB510867 AB510804 AB510823
HKAS 86605, 901582 Slovenia KT822337 KT822439
HAt1S5 Ukraine HQ232292 HQ285906 HQ232284
ATMUS2 USA AY213588 JF313113 AY509189, AY509190
Bhutanese Group 2 CMW10581 Bhutan AY554329 FJ875699 AY624365
Chinese Biological species C CMW31123 China KM205284 KM205337
CMW31124 China KM205285 KM205337
Chinese Biological species F CMW31127 China KM205286 KM205339
 

 

CMW31128 China KM205287 KM205340
Chinese Biological species H CMW31136 China KM205293 KM205346
CMW31138 China KM205294 KM205347
Chinese Biological species J CMW31140 China KM205296 KM205349
CMW31142 China KM205297 KM205350
Chinese Biological species L CMW31144 China KM205298 KM205351
CMW31145 China KM205299 KM205352
Chinese Biological species N CMW31146 China KM205300 KM205353
CMW31148 China KM205301 KM205354
Chinese Biological species O CMW31150 China KM205302 KM205355
CMW31151 China KM205303 KM205356
Chinese Lineage 1 HKAS 86615 China KT822315 KT822384
HKAS 86621 China KT822306 KT822386
Chinese Lineage 2 HKAS 86623 China KT822318 KT822363
HKAS 86551 China KT822279 KT822367
Chinese Lineage 3 HKAS 86613 China KT822319 KT822388
HKAS 86614 China KT822305 KT822391
Chinese Lineage 4 HKAS 86602 China KT822308 KT822378
HKAS 86606 China KT822281 KT822359
Chinese Lineage 5 HKAS 86574 China KT822324 KT822361
HKAS 86574 China KT822327 KT822364
Chinese Lineage 6 HKAS 86570 China KT822320 KT822402
HKAS 86571 China KT822288 KT822404
Chinese Lineage 7 HKAS 83303 China KU378047 KT822437
HKAS 83361 China KU378048 KT822436
Japanese Nag. E 94-2-1 Japan AB510888 AB510768 AB510840
2000-71-13 Japan AB510879 AB510773 AB510832

 

Fig. 2 Phylogenetic tree generated by maximum likelihood analysis of combined ITS-IGS-tef1 sequence data of Armillaria species. Related sequences were obtained from GenBank. One hundred and thirty-nine strains are included in the analyses, which comprise 4557 characters including gaps. The tree was rooted with Guyanagaster lucianii (G31.4) and Guyanagaster necrorhizus (MCA 3950). Single gene analyses were carried out to compare the topology of the tree and clade stability. Tree topology of the ML analysis was similar to the MP and BYPP. ML phylogenetic tree inference was performed using RAxML version 8.2.12 on the CIPRES web server, using a mixed-model analysis and the GTRCAT model of substitution. The four partitions were defined as ITS, IGS, tef1 exons and tef1 introns. The best scoring RAxML tree with a final likelihood value of −25308.198187 is presented. The matrix had 1957 distinct alignment patterns, with 65.74% of undetermined characters or gaps. Estimated base frequencies of ITS were as follows: A =0.227071, C =0.203923, G =0.235701, T =0.333305; substitution rates AC =0.628852, AG=3.751709, AT =1.365607, CG =1.467905, CT =2.788595, GT = 1.000000. Estimated base frequencies of IGS were as follows: A =0.244624, C =0.196588, G =0.242370, T =0.316418; substitution rates AC =0.954911, AG=3.055115, AT =1.041498, CG =1.278095, CT = 3.421100, GT = 1.000000. Estimated base frequencies of tef1 exons were as follows: A =0.228587, C =0.301128, G =0.255865, T =0.214420; substitution rates AC =0.905728, AG=3.660986, AT =1.564184, CG =0.648739, CT = 28.048363, GT = 1.000000. Estimated base frequencies of tef1 introns were as follows: A =0.215042, C =0.222693, G =0.185633, T =0.376631; substitution rates AC =1.170263, AG=5.878084, AT =0.847943, CG =1.087990, CT = 5.095797, GT = 1.000000; gamma distribution shape parameter α =0.1000000000. The maximum parsimonious dataset consisted of 2908 constant, 1172 parsimony-informative and 477parsimony-uninformative characters. The parsimony analysis: CI = 0.610, RI = 0.861, RC = 0.525, HI = 0.390 in the first tree. Bayesian posterior probability was performed using the Markov chain Monte Carlo (MCMC) method implemented in MrBayes 3.2.6 with a mixed-model partition identical to the ones defined in the ML analysis. The best-fit nucleotide substitution model was separately determined for each partition with jModeltest version 2.1.10 on CIPRES, using the Akaike Information Criterion. K80+I, K80+I, SYM+G and HKY+G were selected as best-fit models for ITS, IGS, tef1 exons and tef1 introns, respectively. At the end of the runs, the average deviation of split frequencies was 0.016675. MP and RAxML bootstrap support value ≥ 50% and BYPP ≥0.95are shown, respectively, near the nodes. Holotype or ex-type strains are in bold.

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