The Co-occurrence and Morphological Continuum Between Ericoid Mycorrhiza and Dark Septate Endophytes in Roots of Six European Rhododendron Species

Ericaceae associate with a wide spectrum of root mycobionts, but the most common are ascomycetous ericoid mycorrhizal fungi and dark septate endophytes (DSE), followed by basidiomycetous fungi and glomeracean arbuscular mycorrhizal fungi. We investigated distribution and morphological diversity of ericoid mycorrhizae (ErM), DSE associations, ectomycorrhizae (EcM) and arbuscular mycorrhizae (AM) in hair roots of six European native Rhododendron species and found that i) while EcM and AM were absent, ErM and DSE associations were simultaneously present in all screened plants; ii) their levels were negatively correlated, suggesting Ericaceae preference for certain root-fungus association in certain habitats; iii) the highest ErM colonization occurred at sites in southern and central Europe, while the highest DSE colonization was found in a subarctic site in northern Finland and in a subalpine site in the Carpathians, suggesting a latitudinal/altitudinal shift in Ericaceae root-fungus associations; iv) some mycelia could simultaneously form structures corresponding to ErM and DSE association, which occasionally resulted in a unique ectendomycorrhizal colonization comprising an intercellular parenchymatous net and intracellular hyphal coils. These results indicate frequent interactions between ErM fungi and DSE in roots of European rhododendrons and a morphological continuum between ErM and DSE associations. The new ectendomycorrhizal type deserves further investigation.     

Experimental evidence of ericoid mycorrhizal potential within Serendipitaceae (Sebacinales)

The Sebacinales are a monophyletic group of ubiquitous hymenomycetous mycobionts which form ericoid and orchid mycorrhizae, ecto- and ectendomycorrhizae, and nonspecific root endophytic associations with a wide spectrum of plants. However, due to the complete lack of fungal isolates derived from Ericaceae roots, the Sebacinales ericoid mycorrhizal (ErM) potential has not yet been tested experimentally. Here, we report for the first time isolation of a serendipitoid (formerly Sebacinales Group B) mycobiont from Ericaceae which survived in pure culture for several years. This allowed us to test its ability to form ericoid mycorrhizae with an Ericaceae host in vitro, to describe its development and colonization pattern in host roots over time, and to compare its performance with typical ErM fungi and other serendipitoids derived from non-Ericaceae hosts. Out of ten serendipitoid isolates tested, eight intracellularly colonized Vaccinium hair roots, but only the Ericaceae-derived isolate repeatedly formed typical ericoid mycorrhiza morphologically identical to ericoid mycorrhiza commonly found in naturally colonized Ericaceae, but yet different from ericoid mycorrhiza formed in vitro by the prominent ascomycetous ErM fungus Rhizoscyphus ericae. One Orchidaceae-derived isolate repeatedly formed abundant hyaline intracellular microsclerotia morphologically identical to those occasionally found in naturally colonized Ericaceae, and an isolate of Serendipita (= Piriformospora) indica produced abundant intracellular chlamydospores typical of this species. Our results confirm for the first time experimentally that some Sebacinales can form ericoid mycorrhiza, point to their broad endophytic potential in Ericaceae hosts, and suggest possible ericoid mycorrhizal specificity in Serendipitaceae.     

锦绣杜鹃菌根真菌rDNA ITS序列分析及接种效应研究

利用rDNA ITS序列对锦绣杜鹃菌根真菌的16个菌株进行了分类分析。根据菌株ITS序列全长计算各菌株间序列相似度和遗传距离,并与GenBank中最相似菌株序列构建系统发育树。结果表明：16个菌株在系统树上聚为3个大分支。其中7个菌株在支持率为100%的基础上与树粉孢属真菌Oidiodendron sp.聚为一类;2个菌株与未鉴定的杜鹃花科植物根系真菌unidentified root associated fungi聚为一类,支持率为100%;其他7个菌株在98%的支持率上与几种未命名的欧石楠类菌根真菌     

Intracellular colonization of Rhododendron and Vaccinium roots by Cenococcum geophilum, Geomyces pannorum and Meliniomyces variabilis

Four in vitro experiments were set up to verify the colonization potential of ectomycorrhizal (EcM) Cenococcum geophilum FR. (strain CGE-4), saprotrophic Geomyces pannorum (LINK) SIGLER & CARMICHAEL (GPA-1) and a frequent root-associated, potentially ericoid mycorrhiza (ErM)-forming Meliniomyces variabilis Hambleton & Sigler (MVA-1) in roots of Rhododendron and Vaccinium. A typical ErM fungus, Rhizoscyphus ericae (Read) Zhuang & Korf (RER-1), was included for comparison. All fungal strains intracellularly colonized rooted Vaccinium microcuttings: GPA-1 occasionally produced hyphal loops similar to ErM, MVA-1 and RER-1 exhibited a typical ErM colonization pattern. CGE-4 hyphae grew vigorously on and around newly formed roots and rarely penetrated turgescent rhizodermal cells forming intracellular loose loops. Rooting of Rhododendron sp. microcuttings was not promoted by any fungal strain except CGE-4, which also promoted the most vigorous growth of Rhododendron ponticum L. seedlings. The widespread EcM fungus C. geophilum has a potential to colonize non-EcM roots and support their development which may influence overall growth of ericaceous plants. As shown for G. pannorum, structures resembling ErM may be formed by fungi that are to date not regarded as ericoid mycorrhizal.     

Molecular detection,community structure and phylogeny of ericoid mycorrhizal fungi

Through traditional culturing and molecular characterization, we have determined that five putative species and 2 polyphyletic assemblages of fungi produce ericoid mycorrhizae in Gaultheria shallon, other Ericaceae and Epacridaceae. Using phylogenetic analysis of ITS2 sequences in GenBank, we have confirmed that most of these fungi occur in North America, Europe, and Australia. The low recovery rate of culturable ericoid mycorrhizal fungi from Gaultheria shallon may partly be explained by the fact that most mycorrhizal root segments contain an unculturable basidiomycete, revealed by direct amplification, cloning, and sequencing of LSU fungal DNA from root. Molecular characterization and phylogenetic analysis are powerful tools in revealing the geographic distribution and identity of ericoid mycorrhizal fungi.     

The Potential of Dark Septate Endophytes to Form Root Symbioses with Ectomycorrhizal and Ericoid Mycorrhizal Middle European Forest Plants

The unresolved ecophysiological significance of Dark Septate Endophytes (DSE) may be in part due to existence of morphologically indistinguishable cryptic species in the most common Phialocephala fortinii s. l.—Acephala applanata species complex (PAC). We inoculated three middle European forest plants (European blueberry, Norway spruce and silver birch) with 16 strains of eight PAC cryptic species and other DSE and ectomycorrhizal/ericoid mycorrhizal fungi and focused on intraradical structures possibly representing interfaces for plant-fungus nutrient transfer and on host growth response. The PAC species Acephala applanata simultaneously formed structures resembling ericoid mycorrhiza (ErM) and DSE microsclerotia in blueberry. A. macrosclerotiorum, a close relative to PAC, formed ectomycorrhizae with spruce but not with birch, and structures resembling ErM in blueberry. Phialocephala glacialis, another close relative to PAC, formed structures resembling ErM in blueberry. In blueberry, six PAC strains significantly decreased dry shoot biomass compared to ErM control. In birch, one A. macrosclerotiorum strain increased root biomass and the other shoot biomass in comparison with non-inoculated control. The dual mycorrhizal ability of A. macrosclerotiorum suggested that it may form mycorrhizal links between Ericaceae and Pinaceae. However, we were unable to detect this species in Ericaceae roots growing in a forest with presence of A. macrosclerotiorum ectomycorrhizae. Nevertheless, the diversity of Ericaceae mycobionts was high (380 OTUs) with individual sites often dominated by hitherto unreported helotialean and chaetothyrialean/verrucarialean species; in contrast, typical ErM fungi were either absent or low in abundance. Some DSE apparently have a potential to form mycorrhizae with typical middle European forest plants. However, except A. applanata, the tested representatives of all hitherto described PAC cryptic species formed typical DSE colonization without specific structures necessary for mycorrhizal nutrient transport. A. macrosclerotiorum forms ectomycorrhiza with conifers but not with broadleaves and probably does not form common mycorrhizal networks between conifers with Ericaceae.     

Fungi associated with hair roots of Rhododendron lochiae (Ericaceae) in an Australian tropical cloud forest revealed by culturing and culture-independent molecular methods

The culturable fungal assemblage associated with hair roots of Rhododendron lochiae (Ericaceae) from a tropical cloud forest in Queensland, Australia was investigated using rDNA internal transcribed spacer (ITS) restriction fragment length polymorphisms (RFLPs) and sequence analysis, and the abilities of the fungi to form ericoid mycorrhizas were tested. DNA was further extracted directly from hair roots and partial fungal ITS products compared with those from the cultured isolate assemblage using denaturing gradient gel electrophoresis (DGGE). A range of ericoid mycorrhizal and non-mycorrhizal fungi was identified using both approaches, with ericoid mycorrhizal fungi found to be taxonomically similar to those associated with Ericaceae in temperate habitats worldwide. Both approaches identified several unique fungi and, although most of the abundant RFLP types identified in the cultured fungal assemblage were also present in DGGE profiles of DNA extracted directly from roots, one the most commonly isolated RFLP types, a putative Xylariaceae taxon, was absent. The data suggest that a combination of culturing and culture-independent approaches may be more efficacious than either method individually.     

Molecular diversity within and between ericoid endophytes from the Ericaceae and Epacridaceae

This study investigated the relationships between ericoid mycorrhizal endophytes of the Ericaceae (Northern Hemisphere) and the Epacridaceae (Australia). Over 200 fungi were isolated from the roots of two species of Epacridaceae from Victoria, Australia. The isolates were divided into 12 groups by morphology on quarter-strength potato dextrose agar. All were slow-growing and most were dematiaceous, but groups varied from white through pink to dark olive. The ITS1–5.8S–ITS2 ribosomal DNA was amplified and sequenced from eight isolates, forming typical ericoid mycorrhizal morphology in Epacris impressa and one nonmycorrhizal isolate. Sequences were compared, by using similarities and maximum-parsimony analysis, with those of Hymenoscyphus ericae (Leotiales) and Oidiodendron species (Hyphomycetes), the most common endophytes of the Ericaceae. Maximum-parsimony analysis produced four clusters: (1) all Oidiodendron species (at least 90% similarity); (2) all five Victorian dark grey-olive isolates (at least 96% similarity); (3) one Victorian isolate and Cistella grevillei (88% similarity); (4) two light-coloured Victorian isolates and H. ericae (81% similarity). This suggests that these isolates from the Epacridaceae do not belong to the same species as those forming ericoid mycorrhiza in the Ericaceae.     

Distribution of ericoid mycorrhizal endophytes and root-associated fungi in neighbouring Ericaceae plants in the field

Three hundred and twenty-seven fungal endophyte isolates were obtained from hair roots of neighbouring Woollsia pungens Cav. (Muell.) and Leucopogon parviflorus (Andr.) Lindl. (both Ericaceae) plants at an Australian dry sclerophyll forest site and mapped according to the root segments from which they were obtained. Restriction fragment length polymorphism (RFLP) analysis of the rDNA internal transcribed spacer (ITS) region indicated that the isolate assemblage comprised 21 RFLP-types (= putative taxa), five of which were shown in gnotobiotic culture experiments to be ericoid mycorrhizal endophytes. While two mycorrhizal RFLP-types were exclusive to either W. pungens or L. parviflorus, RFLP-type VI was isolated from both hosts. This putative taxon had strong ITS sequence identity with Helotiales ericoid mycorrhizal ascomycetes, comprised ca. 75% of all isolates from each plant and was spatially widespread in both root systems. Inter-simple sequence repeat PCR analysis indicated that two and four genotypes of RFLP-type VI were present in the W. pungens and L. parviflorus root systems respectively, however single genotypes appeared to dominate each root system. One genotype was present in both root systems. The data suggest that assemblages of ericoid mycorrhizal fungi from hair roots of individual Ericaceae plants in dry sclerophyll forest habitats are characterised by relatively low genetic diversity.     

Ericoid mycorrhizal fungi are common root inhabitants of non-Ericaceae plants in a south-eastern Australian sclerophyll forest

Fungi were isolated from the roots of 17 plant species from the families Apiaceae, Cunoniaceae, Cyperaceae, Droseraceae, Fabaceae-Mimosoideae, Lomandraceae, Myrtaceae, Pittosporaceae, Proteaceae and Stylidiaceae at a sclerophyll forest site in New South Wales, Australia. Internal transcribed spacer (ITS) restriction fragment length polymorphism (RFLP) and sequence comparisons indicated that the isolated fungi had affinities to a range of ascomycetes, basidiomycetes and zygomycetes. Four RFLP types had closest affinities to previously identified Helotiales ericoid mycorrhizal (ERM) or Oidiodendron spp. Isolates representing six RFLP types, which were variously isolated from all 17 plant species, formed ERM coils in hair root epidermal cells of Woollsia pungens (Ericaceae) under gnotobiotic conditions. Three of these isolates formed intercellular hyphae, intracellular hyphae and/or microsclerotia, which are typical of dark septate endophyte infection, in roots of Stylidium productum (Stylidiaceae), indicating an ability to form different types of association with roots of different hosts. Overall the data indicate that a broad range of plant taxa may act as repositories for ERM fungi in sclerophyll forest soil.     

Ericoid fungal diversity: Challenges and opportunities for mycorrhizal research

Ericoid mycorrhiza occur only within the plant family Ericaceae, yet are globally widespread and contribute to carbon and nutrient cycling in many habitats where harsh conditions limit decomposition and plant nutrient uptake. An increasingly diverse range of fungi are recognized as ericoid symbionts and patterns in the distribution of ericoid taxa are beginning to emerge across scales. However, the true diversity of ericoid mycorrhizal fungi remains unresolved due to limited sampling from some regions and challenges associated with delineating mycorrhizal taxa from the broader fungal community associated with ericoid plants. Interpreting patterns in the diversity and distributions of ericoid mycorrhizal fungi will ultimately require improved understanding of their functional ecology and functional diversity, which is currently limited to a few well studied species. Fortunately, many ericoid taxa are amenable to experimental manipulation and continued ericoid mycorrhizal research promises to improve general understanding of the ecology and evolution of mycorrhizal symbioses.     

Assemblages of ericoid mycorrhizal and other root-associated fungi from Epacris pulchella (Ericaceae) as determined by culturing and direct DNA extraction from roots

Ericoid mycorrhizal fungal endophytes form mycorrhizal associations with Ericaceae plant taxa and are regarded as essential to the ecological fitness of the plants in extremely nutrient-poor soils worldwide. We isolated fungi from roots of Epacris pulchella (Ericaceae) in a south-eastern Australian sclerophyll forest and compared rDNA internal transcribed spacer (ITS) restriction fragment length polymorphisms (RFLPs) and sequences for the cultured isolate assemblage with fungi identified in DNA extracted directly from the same root systems by cloning or denaturing gradient gel electrophoresis (DGGE). The most abundant RFLP types in the cultured isolate assemblage were identified as putative ericoid mycorrhizal ascomycete endophytes, and these also represented the most abundant RFLP types in the cloned assemblage and the most intense bands in DGGE profiles. Each method identified unique taxa, notably putative basidiomycetes in the DNA extracted directly from E. pulchella roots. However, the relative abundance of these was low.     

Diversity of root-associated fungal endophytes in Rhododendron fortunei in subtropical forests of China

To investigate the diversity of root endophytes in Rhododendron fortunei, fungal strains were isolated from the hair roots of plants from four habitats in subtropical forests of China. In total, 220 slow-growing fungal isolates were isolated from the hair roots of R. fortunei. The isolates were initially grouped into 17 types based on the results of internal transcribed spacer-restriction fragment length polymorphism (ITS-RFLP) analysis. ITS sequences were obtained for representative isolates from each RFLP type and compared phylogenetically with known sequences of ericoid mycorrhizal endophytes and selected ascomycetes or basidiomycetes. Based on phylogenetic analysis of the ITS sequences in GenBank, 15 RFLP types were confirmed as ascomycetes, and two as basidiomycetes; nine of these were shown to be ericoid mycorrhizal endophytes in experimental cultures. The only common endophytes of R. fortunei were identified as Oidiodendron maius at four sites, although the isolation frequency (3–65%) differed sharply according to habitat. Phialocephala fortinii strains were isolated most abundantly from two habitats which related to the more acidic soil and pine mixed forests. A number of less common mycorrhizal RFLP types were isolated from R. fortunei at three, two, or one of the sites. Most of these appeared to have strong affinities for some unidentified root endophytes from Ericaceae hosts in Australian forests. We concluded that the endophyte population isolated from R. fortunei is composed mainly of ascomycete, as well as a few basidiomycete strains. In addition, one basidiomycete strain was confirmed as a putative ericoid mycorrhizal fungus.     

Ericoid mycorrhizal fungi: some new perspectives on old acquaintances

Many ericaceous species colonize as pioneer plants substrates ranging from arid sandy soils to moist mor humus, in association with their mycorrhizal fungi. Thanks to the symbiosis with ericoid mycorrhizal fungi, ericaceous plants are also able to grow in highly polluted environments, where metal ions can reach toxic levels in the soil substrate. For a long time this mycorrhizal type has been regarded as an example of a highly specific interaction between plants and fungi. More recent studies have been challenging this view because some ericoid mycorrhizal endophytes seem also able to colonise plants from very distant taxa. A molecular approach has allowed the investigation of genetic diversity and molecular ecology of ericoid mycorrhizal fungi, and has revealed that ericaceous plants can be very promiscuous, with multiple occupancy of their thin roots. The molecular analysis of sterile morphotypes involved in this symbiosis has also led to deeper understanding of the species diversity of ericoid fungi. Genetic polymorphism of ericoid fungi is wider than previously thought, and often increased by the presence of Group I introns in the nuclear small subunit rDNA.     

Diversity of fungi in hair roots of Ericaceae varies along a vegetation gradient

Ericaceous dwarf shrubs including Calluna vulgaris and Vaccinium spp. occur both in open heathland communities and in forest ecosystems as understory vegetation. Ericaceous shrubs were once thought to form ericoid mycorrhizal associations with a relatively narrow range of ascomycetous fungi closely related to, and including, Rhizoscyphus ericae. However, perceptions have recently changed since the realization that a broader range of ascomycete fungi, and in some cases basidiomycete fungi, can also form associations with the roots of ericaceous plants. We used a combination of molecular approaches, including denaturing gradient gel electrophoresis, terminal restriction fragment length polymorphism, cloning and sequencing, to investigate the diversity of fungi associated with C. vulgaris roots collected across a heathland/native Scots pine forest vegetation gradient. We also determined differences in fungal community composition between roots of co-occurring C. vulgaris and Vaccinium myrtillus in the forest understory. Collectively, the data show that a large diversity of potentially ericoid mycorrhizal fungal taxa associate with roots of C. vulgaris and V. myrtillus, and that ascomycetes were about 2.5 times more frequent than basidiomycetes. The assemblages of fungi associated with C. vulgaris and V. myrtillus were different. In addition, the community of fungi associated with C. vulgaris hair roots was different for samples collected from the forest, open heathland and a transition zone between the two. This separation was partly, but not entirely, due to the occurrence of typical ectomycorrhizal basidiomycetes associated with the hair roots of C. vulgaris in the forest understory. These data demonstrate that forest understory ericaceous shrubs associate with a diverse range of ascomycete and basidiomycete taxa, including typical ectomycorrhizal basidiomycetes.     

杜鹃花科植物菌根的研究进展

杜鹃花科Ericaceae植物可与土壤真菌形成杜鹃花类菌根ericoid mycorrhizas (ERM)共生体,且广泛分布于全球不同的陆地生态系统,特别是在贫瘠、酸性等严酷的环境中占优势.杜鹃花科植物菌根类型多样,绝大多数宿主具有ERM,还有少量宿主具有其他类型的菌根结构,且常与暗隔内生菌(dark septate...     

VESICULAR-ARBUSCULAR MYCORRHIZAE IN HAWAIIAN ERICALES

Vesicular-arbuscular mycorrhizae (VAM) are reported for the first time in four species of Hawaiian Ericales, Vaccinium calycinum, V. dentatum, and V. reticulatum of the Ericaceae and Styphelia tameiameiae of the Epacridaceae. The coarse roots (> 1.5 mm diam) of many specimens were densely colonized by VAM fungi, with up to 90% of the length of roots containing arbuscules, vesicles, coils, and internal hyphae. Spores of an undescribed Glomus sp. were associated with two species of Vaccinium. The hair roots of all species bore the ericoid mycorrhizae typical of certain families of this order. The high frequency of VAM in Hawaiian populations of Ericales suggests that ancestral Ericales possessed the capacity to form both VA and ericoid mycorrhizae. An evolutionary sequence of mycorrhizal dependency in the Ericales is presented.     

Anatomy and ultrastructure of mycorrhizal associations of neotropical Ericaceae

Ericaceae are obligatory associated with symbiotic fungi forming several, distinctive categories of mycorrhizas. While ericoid, arbutoid, and monotropoid mycorrhizas are known since many years from ericads of the northern hemisphere and the ericoid mycorrhiza also from Australia, a further mycorrhizal category with hyphal sheath, Hartig net, and intracellular colonization was described by us recently and termed cavendishioid mycorrhiza because it was found on Cavendishia nobilis, a species belonging to the Andean clade (Vaccinioideae) of Ericaceae. As the previous findings indicated a correlation between the mycorrhizal category and the systematic position of Ericaceae, we tested the hypothesis that other ericads of the Andean clade might also form cavendishioid mycorrhizas, while ericads occurring in the same area but not belonging to the Andean clade might not. Mycorrhizas of 20 different ericaceous species, 15 belonging to the Andean clade and 5 to other Vaccinioideae or Ericoideae, were sampled in the tropical mountain rain forest area of South Ecuador and investigated by light and electron microscopy. All the 15 members of the Andean clade ericads displayed a hyphal sheath, as well as inter- and intracellular colonization by hyphae as was found on Cavendishia previously. The five species not belonging to the Andean clade ericads displayed only intracellular colonization by hyphae and hence were typical ericoid mycorrhizal. Ultrastructural studies revealed Sebacinales and ascomycetes as mycorrhiza formers in both associations even within one single cell. The results thus support the hypothesis that the Andean clade of Ericaceae forms mycorrhizas distinct from the arbutoid category and most likely presents an independent evolutionary line in the Ericaceae derived from the ericoid mycorrhizas, justifying the new term “cavendishioid mycorrhiza”.     

The cultivable endophytic community of Norway spruce ectomycorrhizas from microhabitats lacking ericaceous hosts is dominated by ericoid mycorrhizal Meliniomyces variabilis

Most of the temperate conifers associate with ectomycorrhizal fungi, but their roots also harbour a wide range of endophytes. We focused on ascomycetes associating with basidiomycetous ectomycorrhizas of Norway spruce in a temperate montane forest in central Europe and found that the majority of the co-associated fungi belonged to the Rhizoscyphus ericae aggregate (REA), being dominated by Meliniomyces variabilis. We further tested the ability of representative isolates to colonize spruce root tips and European blueberry (Vaccinium myrtillus) hair roots in an agar system as well as their effect on blueberry growth in a peat-agar system. M. variabilis intracellularly colonized spruce (Picea abies) root tip cortex, formed ericoid mycorrhizas in blueberry and enhanced blueberry shoot and root growth in comparison with non-inoculated plants. Our findings suggest that spruce ectomycorrhizas may represent selective niches for ericoid mycorrhizal fungi in habitats lacking suitable ericaceous hosts.     

Sebacinales are common mycorrhizal associates of Ericaceae

Previous reports of sequences of Sebacinales (basal Hymenomycetes) from ericoid mycorrhizas raised the question as to whether Sebacinales are common mycorrhizal associates of Ericaceae, which are usually considered to associate with ascomycetes. Here, we sampled 239 mycorrhizas from 36 ericoid mycorrhizal species across the world (Vaccinioideae and Ericoideae) and 361 mycorrhizas from four species of basal Ericaceae lineages (Arbutoideae and Monotropoideae) that do not form ericoid mycorrhizas, but ectendomycorrhizas. Sebacinales were detected using sebacinoid-specific primers for nuclear 28S ribosomal DNA, and some samples were investigated by transmission electron microscopy (TEM). Diverging Sebacinales sequences were recovered from 76 ericoid mycorrhizas, all belonging to Sebacinales clade B. Indeed, some intracellular hyphal coils had ultrastructural TEM features expected for Sebacinales, and occurred in living cells. Sebacinales belonging to clade A were found on 13 investigated roots of the basal Ericaceae, and TEM revealed typical ectendomycorrhizal structures. Basal Ericaceae lineages thus form ectendomycorrhizas with clade A Sebacinales, a clade that also harbours ectomycorrhizal fungi. This further supports the proposition that Ericaceae ectendomycorrhizas involve ectomycorrhizal fungal taxa. When ericoid mycorrhizas evolved secondarily in Ericaceae, a shift of mycobionts occurred to ascomycetes and clade B Sebacinales, hitherto not described as ericoid mycorrhizal fungi.