Ectomycorrhizae of Tomentella albomarginata (Thelephoraceae) on Scots pine

 The ectomycorrhizae of Tomentella albomarginata are comprehensively described and compared to ectomycorrhizae of other Tomentella species and to ectomycorrhizae of some members of Thelephoraceae ss. Stalpers and Bankeraceae ss. Stalpers. The ectomycorrhizae of T. albomarginata are characterized by a hyphal net lying on a pseudoparenchymatous mantle surface, by tubular outgrowths of irregularly angular mantle cells, and by clamp-bearing emanating hyphae. Accepted: 15 July 1995     

Four ectomycorrhizae of Pyronemataceae (Pezizomycetes) on Chinese Pine (<Emphasis Type="Italic">Pinus tabulaeformis</Emphasis>): morpho-anatomical and molecular-phylogenetic analyses

Morphological and anatomical characters of four ectomycorrhizae with affinities to the genera Humaria, Geopora, and Trichophaea of Pyronemataceae (Pezizomycetes, Ascomycota) on Chinese Pine (Pinus tabulaeformis) are described. The ectomycorrhizae are yellowish brown to brown, and have pseudoparenchymatous outer mantle layers and partially warty emanating hyphae with thick walls and without clamps. Intrahyphal hyphae are present, and no rhizomorphs are formed. The four ectomycorrhizae are distinguishable by differences in cell shape of outer mantle layers and the presence of cystidia. Ectomycorrhizae of a possible Humaria species (Pinirhiza humarioides) lack cystidia and have irregularly inflated cells on the outer mantle layer that are connected with thin septa. The two ectomycorrhizae showing probable affinities to Geopora species (“P. daqingensis” and “P. geoporoides”) possess row-like arranged cells in the outer mantle layer and cell heaps, and differ by the presence or absence of cystidia as well as by the structure of the inner mantle layers. Ectomycorrhizae likely having been formed by a Trichophaea species (“P. trichophaeoides”) have oval to polygonal cells and no cystidia. The possible taxa affiliations were assessed by molecular-phylogenetic analyses of the internal transcribed spacer (ITS) and partial large subunit (LSU) nrDNA. Morphological and anatomical characters are discussed against the background of the LSU phylogeny.     

DEEMY – the concept of a characterization and determination system for ectomycorrhizae

 A considerable amount of data has been published on morphological and anatomical characteristics of ectomycorrhizae but these are dispersed in several, sometimes not easily available, journals. The few keys that exist are mostly based upon host tree genera. No comprehensive determination tools for non-experts are available. An information system for specific characters of ectomycorrhizae and an interactive key are now provided by DEEMY on CD-ROM. Accepted: 6 May 1997     

In vitro synthesis of Pisolithus-Eucalyptus ectomycorrhizae: synchronization of lateral tip emergence and ectomycorrhizal development

 A simple and reproducible in vitro system is described for the synthesis of Pisolithus-Eucalyptus grandis ectomycorrhizae. Hyphal discs from actively growing colonies were placed in large petri dishes containing minimum nutrient agar overlaid with cellophane and allowed to grow for 7 days. Seeds were then surface sterilized and placed above the expanding fungal colonies and the plates slanted. Seedlings that germinated and grew in the presence of fungal hyphae had twice as many lateral root tips as seedlings that germinated before they were transferred onto hyphal mats. In addition, the lateral root tips of inoculated seedlings had a faster maturation rate and emerged closer to the primary root apex than non-inoculated seedlings. All lateral tips emerged in contact with fungal hyphae and the differentiation of ectomycorrhizae was followed by examining lateral tips basipetally along a single primary root. Typical ectomycorrhizae had formed on 4-day-old lateral tips, i.e. a mantle, radially elongated epidermal cells and a Hartig net commencing about 0.3 mm behind the lateral root apex. Thereafter, the mantle continued to thicken and the apical meristem diminished. The Hartig net often surrounded the apex of 11- to 12-day-old lateral root tips. This model system will facilitate detailed studies on synchronized ectomycorrhizal development and associated molecular and biochemical changes. Accepted: 12 January 1996     

Bacterial community structure and colonization patterns of Fagus sylvatica L. ectomycorrhizospheres as determined by fluorescence in situ hybridization and confocal laser scanning microscopy

) grown in natural forest soil in southern Germany was examined by fluorescence in situ hybridization (FISH) using fluorescent oligonucleotide probes, targeting phylogenetic relevant sequences of the 16S and 23S rRNA. Lactarius subdulcis, L. vellereus, L. rubrocinctus and Laccaria amethystina were found to be the prevalent fungi forming ectomycorrhizae with F. sylvatica. For FISH studies using confocal laser scanning microscopy, oligonucleotide probes labeled with carboxymethylindocyanine-succinimidyl ester allowed detection of associated bacteria, because the autofluorescence of ectomycorrhiza samples could be overcome in the infrared. Bacteria of the α-, β and γ-subclasses of the proteobacteriawere detected in high numbers on mantle surfaces, while members of other phylogenetically defined groups were found in smaller numbers. This contrasts with previous published results on the cultivation of mycorrhiza-associated bacteria. Hybridizing bacteria were also found within damaged cells of the hyphal mantle of L. rubrocinctus, as well as on emanating hyphae of L. amethystina. Using a newly developed extraction protocol for bacteria associated with ectomycorhizas, the two most common fungi on F. sylvatica, L. vellereus and L. subdulcis, were mostly associated with members of the α- and β-subclasses of the proteobacteria. The proportion of hybridizing bacteria varied between the two ectomycorrhizae, which were thus host to distinct populations of bacteria.     

Accumulation of Heavy Metals by Ectomycorrhizal Fungi Colonizing Birch Trees Growing in an Industrial Desert Soil

The results of analyses conducted to determine contents of Cd(II) and Pb(II) in mushrooms of mycorrhizal fungi and selected parts of birches growing in an industrial desert surrounding a nonferrous works are presented in this study. The fruiting bodies of fungi accumulated several times higher contents (up to 80 μg g⁻¹ dry weight) of Cd(II) compared to those found in the soil (20 μg g⁻¹ dry weight). In contrast, the mushroom contents of Pb(II) were only slightly increased (up to 895 μg g⁻¹ dry weight) than those present in the soil (500 μg g⁻¹ dry weight). However, fivefold higher concentrations of the metals were found in the mycorrhizal roots. Comparing the distribution of the metals analysed, the protective role of the ectomycorrhizae in relation to the host tree was indicated. Mycorrhizal fungi persistently fixed heavy metals, forming an efficient biological barrier that reduced movement of the metals in birch tissues.     

Ectomycorrhizal fungi of Pinus pinaster

A study was undertaken to determine the ability to form ectomycorrhizae with Pinus pinaster Ait. in pure culture syntheses of 98 isolates of putative mycorrhizal fungi, mainly collected in northern Spain. A total of 35 species in 16 genera — Amanita, Cenococcum, Collybia, Cortinarius, Hebeloma, Laccaria, Lactarius, Lyophyllum, Melanogaster, Paxillus, Pisolithus, Rhizopogon, Scleroderma, Suillus, Thelephora and Xerocomus — formed ectomycorrhizae. Many of these fungal species were not previously reported as symbiotic with Pinus pinaster. Results obtained increase the range of potential fungal candidates for inoculation of nursery seedlings.     

Ectomycorrhizae of Sarcodon imbricatus on Norway spruce and their chlamydospores

Summary The ectomycorrhizae of Sarcodon imbricatus are comprehensively described and compared to other ectomycorrhizae of Thelephoraceae species. Sarcodon imbricatus ectomycorrhizae are distinguished from all previously described ectomycorrhizae by the unique shape of their chlamydospores.Considered as part XXXVI of the series Studies on ectomycorrhizae; part XXXV: Weiss (1991)     

Ectomycorrhizae of Phellodon niger on Norway spruce and their chlamydospores

The ectomycorrhizae of Phellodon niger are comprehensively described and compared to other ectomycorrhizae of Thelephoraceae species. P. niger ectomycorrhizae are distinguished from all previously described ectomycorrhizae by the unique shape of their chlamydospores.Considered as part XLIII of the series Studies on ectomycorrhizae; part XLII: Raidl and Agerer (1992)     

Morphological and molecular comparison of white truffle ectomycorrhizae

In the present study, white truffle ectomycorrhizae (EM) collected in deciduous forests (Populus, Quercus, and Fagus) from Hungary were characterized by morphological–anatomical and molecular methods. Our investigations suggest that the EM of white truffles (e.g., Tuber rapaeodorum, Tuber puberulum, Tuber rufum) are common and abundant members of the forest communities in the area. The ITS sequences of 14 EM specimens and 46 additional fruitbody sequences from the GenBank were clustered into four main groups in phylogenetic analyses. In the ITS-1 region, a characteristic indel pattern was found, which supports the clades. Although our analyses indicate definite genetic distance between the groups of the phylogenetic tree, these clades do not correspond to the traditional taxons identified by fruitbody characteristics. Comparison of the ectomycorrhizae shows that neither is mycorrhizal anatomy a good tool to separate the groups, because the characters (like the epidermoid or angular mantle structure, cell wall thickness, the sape and size of cystidia) are too variable and overlap between the clades. The interspecific similarity, observed both in ectomycorrhizal and fruitbody characters, strengthen the sensu lato morpho-species concept of this group. Our study, which combines comprehensive molecular and anatomical approach to characterize and identify ectomycorrhizae of white truffles from natural samples, stress out the need of the taxonomical revision of this group.     

In vitro cultivation and fruit body formation of the black bolete, Phlebopus portentosus, a popular edible ectomycorrhizal fungus in Thailand

The tropical black bolete Phlebopus portentosus is highly favored in the cuisine of northern Thailand. It is suspected to form ectomycorrhizae with many host trees. Mycelium of P. portentosus isolated from a basidiome in Chiang Rai Province in 2003 grew well on modified Gamborg, modified Melin–Norkans, and Murashige and Skoog media at 30°C and at pH 4. In vitro fructification of P. portentosus on sorghum grain medium without a host plant is presented for the first time. Basidiomes emerged 3 months after inoculation on the medium, and the produced basidiospores germinated on agar, indicating the completion of its life cycle in vitro without a host. Five putative host plants (Castanopsis tribuloides, Dipterocarpus alatus, Dimocarpus longan, Pinus kesiya, and Syzygium cumini) were inoculated with mycelium on sorghum grain medium in a greenhouse to confirm its ectomycorrhizal status. Ectomycorrhizal roots were observed only on Pinus kesiya, suggesting that P. portentosus may be facultatively ectomycorrhizal. Identification of the synthesized ectomycorrhizae was confirmed by PCR amplification of ITS with a designed specific primer (HAR2A).     

Effect of heavy metal pollution on mycorrhizal colonization and function: physiological, ecological and applied aspects

 High concentrations of heavy metals in soil have an adverse effect on micro-organisms and microbial processes. Among soil microorganisms, mycorrhizal fungi are the only ones providing a direct link between soil and roots, and can therefore be of great importance in heavy metal availability and toxicity to plants. This review discusses various aspects of the interactions between heavy metals and mycorrhizal fungi, including the effects of heavy metals on the occurrence of mycorrhizal fungi, heavy metal tolerance in these micro-organisms, and their effect on metal uptake and transfer to plants. Mechanisms involved in metal tolerance, uptake and accumulation by mycorrhizal hyphae and by endo- or ectomycorrhizae are covered. The possible use of mycorrhizal fungi as bioremediation agents in polluted soils or as bioindicators of pollution is also discussed. Accepted: 23 June 1997     

Ectomycorrhizal syntheses with Picea abies and three fungal species: a case study on the use of an in vitro technique to identify naturally occurring ectomycorrhizae

Ectomycorrhizal syntheses between Picea abies and the fungal associates Scleroderma citrinum, Boletus luridus, and Tricholoma vaccinum were carried out using Melin's Erlenmeyer flask technique. The symbioses of S. citrinum were characterized by a mantle composed of an outer prosenchymatous and an inner synenchymatous layer. The mantles of B. luridus and T. vaccinum were solely prosenchymatous. Rhizomorphs were produced in all treatments, but only in association with S. citrinum were they differentiated with additional, enlarged hyphae. All synthesized ectomycorrhizae were white or whitish to light orange and greyishorange. On large-scale root sampling in two differing Picea abies forests in Switzerland, nine out of a total of 22 morphological types of ectomycorrhizae were white or yellow in colour and were, therefore, comparable with the synthesized ectomycorrhizae. These nine natural types generally had distinct mantle features (irregular synenchyma, gelatinous matrix, cystides, thick-walled hyphae), but mostly lacked clamp connections. Synthesized ectomycorrhizae, on the other hand, lacked distinct mantle characteristics and always had clamp connections. Natural and synthesized white or yellow ectomycorrhizae did not coincide morphologically and thus identification of the fungal partners of natural symbioses by means of in vitro-synthesis with potential ectomycorrhizal fungi was not possible in the present study.     

The extraction and quantification of ergosterol from ectomycorrhizal fungi and roots

Recently, ergosterol analysis has been used to quantify viable fungal biomass in resynthesized ectomycorrhizae. An objective of our study was to quantify ergosterol in a range of ectomycorrhizal isolates under differing growth conditions. In addition, we tested the applicability of the method on field-collected roots of ectomycorrhizal and vesicular-arbuscular (VA) mycorrhizal plants. Quantification of sitosterol as a biomass indicator of plant roots was also undertaken. Ergosterol was not detected in roots of uninoculated Betula populifolia seedlings, and sitosterol was not detected in an ectomycorrhizal fungal isolate but was present in birch roots. Ergosterol was produced in all isolates examined, which represented the major orders of ectomycorrhizal fungi. The range of values obtained, from 3 to nearly 18 g ergosterol mg^-1 dry mass, agrees well with reported values for other mycorrhizal and decomposer fungi. Hyphal ergosterol was the same during growth on phytic acid and KH₂PO₄. Reduction of growth temperature from 25° C to 15° C had little effect on ergosterol content of cultures harvested at similar growth stages. Ergosterol and sitosterol were detected in field-collected ectomycorrhizae of B. populifolia and Pinus sylvestris and VA mycorrhizae of Acer rubrum and Plantago major. Both ergosterol content and ergosterol to sitosterol ratios were significantly lower in VA mycorrhizae than ectomycorrhizae. Calculations of viable fungal biomass associated with field-collected roots were in agreement with those reported by others using the method on resynthesized ectomycorrhizae. Estimates of total mass could be obtained for field-collected B. populifolia roots by a simultaneously using ergosterol to estimate fungal biomass and sitosterol to estimate root mass. Some potential applications and limitations of sterol quantification in studies of mycorrhizal physiology and ecology are discussed.     

Exploration types of ectomycorrhizae

There is a need to quantify and qualify the ability of ectomycorrhizae to improve tree growth and nutrition and, in particular, to define criteria to classify ectomycorrhizae with respect to ecologically relevant features. Whereas the numbers of ectomycorrhizae and morphotypes give useful information when related to root biomass, root length or soil volume, the development and differentiation of the extramatrical mycelium may represent important predicative features relevant to the ecological classification of ectomycorrhizae. Here, different exploration types of ectomycorrhizae are distinguished based on the amount of emanating hyphae or the presence and differentiation of rhizomorphs. Their putative ecological importance is discussed. Accepted: 27 March 2001     

New data on ectomycorrhizae and soils of the Chinese truffles Tuber pseudoexcavatum and Tuber indicum, and their impact on truffle cultivation

Chinese truffles serve as a good complement to the market for Tuber melanosporum (Périgord black truffle). However, Chinese truffles could be introduced accidentally or fraudulently into the plantations of Mediterranean truffles, and they could have a negative effect on truffle production and natural ecosystems. The study of Tuber species from China which are commercialized in Europe began 14 years ago. Tuber pseudoexcavatum was proposed as a new species, and this has been validated by some authors based on molecular and phylogenetic studies. We synthesize their ectomycorrhizae using samples from the type collection, and we compare T. pseudoexcavatum and Tuber indicum ectomycorrhizae. The ectomycorrhizae of these species have a morphology which is related to the ectomycorrhizae of T. melanosporum. We provide useful information for the rapid screening of the above-mentioned Chinese truffles ectomycorrhizae, for the quality control of commercial plants mycorrhized with Tuber. Moreover, we analyze the soil tolerance and the host plant affinity of T. pseudoexcavatum and T. indicum, in order to assess the capacity of both Chinese truffles to penetrate T. melanosporum plantations and habitats.     

Exploration type-specific standard values of extramatrical mycelium – a step towards quantifying ectomycorrhizal space occupation and biomass in natural soil

The present study aims at providing standard values for the exploration type (ET)-specific quantification of extramatrical mycelium (EMM) of ectomycorrhizal fungi applicable to ecological field studies. These values were established from mycelial systems of ectomycorrhizae (ECM) synthesized in rhizotrons with near-to-natural peat substrate. Based on image analysis, the “Specific Potential Mycelial Space Occupation” (sPMSO), i.e. the ET-specific complete area that is covered by the EMM systems (mm² cm⁻¹ ECM⁻¹), and the “Specific Actual Mycelial Space Occupation” (sAMSO), i.e. the projection area of mycelial systems (mm² cm⁻¹ ECM⁻¹), were analyzed as an extension of a previously described approach. The “Specific Extramatrical Mycelial Length” (sEML) [m cm⁻¹ ECM⁻¹] and the “Specific Extramatrical Mycelial Biomass” (sEMB) (μg cm⁻¹ ECM⁻¹) were calculated for each of the ET via the proportion of hyphal projected area, hyphal length and biomass, the latter two being derived from previous measurements on Piloderma croceum, a “Medium-Distance” (MD)-ET. Both sPMSO and sAMSO were highest for the “Long-Distance” (LD)-ET, whereas those of the “Short-Distance” (SD)-ET and MD-ET were similar, although showing high variation. In contrast, mycelial density per occupied area of the MD-ET was twice as high as that of the LD-ET. Proportional to the sAMSO, the EMM length and biomass differed considerably between the three ET with values of the MD-ET being 1.9 times higher than those of SD-ET, and those of the LD-ET being 15 times higher than those of the SD-ET. These standards in relation to ECM length may ease quantification of mycelial space occupation and biomass in a relatively simple way. Thereby, the ET-specific contribution of EMM can be distinguished—also of non-cultivable species—and up-scaling to large-scale estimation of cost/benefit relations is possible.     

Ectomycorrhizae between <Emphasis Type="Italic">Alnus acuminata</Emphasis> H.B.K. and <Emphasis Type="Italic">Naucoria escharoides</Emphasis> (Fr.:Fr.) Kummer from Argentina

Field ectomycorrhizae of Naucoria escharoides on Alnus acuminata ("andean alder", "aliso del cerro") are described in detail for the first time. Naturally occurring ectomycorrhizal roots were sampled beneath sporocarps of N. escharoides. The samples were taken from four natural forest plots at two homogeneous A. acuminata sites (Tucumán and Catamarca Provinces, Argentina). The ectomycorrhizae were characterized morphologically and compared by means of PCR/RFLP analysis of the internal transcribed spacer region of the nuclear rDNA. The most important morphological features of the ectomycorrhizae are a white to pale yellow mantle, simple to monopodial branches, hyaline emanating hyphae, abundant hyphal bundles emerging more or less perpendicularly from a plectenchymatous mantle, and an acute or rounded apex with or without a mantle. N. escharoides fruitbodies have white basal mycelium with emanating hyphae similar to those of andean alder ectomycorrhizae. The RFLP profiles of sporocarps and mycorrhizae were the same.