Ingeborg Haug

Atractiellomycetes belonging to the ‘rust’ lineage (Pucciniomycotina) form mycorrhizae with terrestrial and epiphytic neotropical orchids

Distinctive groups of fungi are involved in the diverse mycorrhizal associations of land plants. All previously known mycorrhiza-forming Basidiomycota associated with trees, ericads, liverworts or orchids are hosted in Agaricomycetes, Agaricomycotina. Here we demonstrate for the first time that Atractiellomycetes, members of the ‘rust’ lineage (Pucciniomycotina), are mycobionts of orchids. The mycobionts of 103 terrestrial and epiphytic orchid individuals, sampled in the tropical mountain rainforest of Southern Ecuador, were identified by sequencing the whole ITS1-5.8S-ITS2 region and part of 28S rDNA. Mycorrhizae of 13 orchid individuals were investigated by transmission electron microscopy. Simple septal pores and symplechosomes in the hyphal coils of mycorrhizae from four orchid individuals indicated members of Atractiellomycetes. Molecular phylogeny of sequences from mycobionts of 32 orchid individuals out of 103 samples confirmed Atractiellomycetes and the placement in Pucciniomycotina, previously known to comprise only parasitic and saprophytic fungi. Thus, our finding reveals these fungi, frequently associated to neotropical orchids, as the most basal living basidiomycetes involved in mycorrhizal associations of land plants.

Xerocomus badius - Picea abies, an ectomycorrhiza of high activity and element storage capacity in acidic soil

Abstract Mycorrhizas were collected from three Norway spruce (Picea abies) stands in southwest Germany, sorted on the morphotype level and analysed by fluorescein diacetate vital fluorescence staining and the accumulation of elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and electron energy-loss spectroscopy (EELS). Xerocomus badius – Picea abies mycorrhizas showed a higher frequency of active hyphal sheaths and a higher potential to store nitrogen, phosphorus, potassium, magnesium, iron and zinc than other mycorrhizal types. Phosphorus and nitrogen were localized by EELS in vacuolar bodies which occurred consistently in the sheath of X. badius mycorrhizas. The results indicate that X. badius is well adapted to acidic stands and that its mycorrhizas are very efficient in uptake and storage of macronutrients.

Some distinctive types of spruce mycorrhizae

SummaryFor examination and recognition of mycorrhizal types, the structure of the hyphal mantle in tangential longitudinal sections has proved to be a valuable feature for investigation. Features of hyphal mantle structure have been used for establishing an identification key. The colour of the hyphal mantle is a helpful additional characteristic, but is not useful as a diagnostic feature because of variations in advanced age and under varying environmental conditions. Rhizomorphs yield good taxonomic characteristics. The Hartig net was uniform for all types examined. When differences were observed they had to be interpreted as different stages of development. Ultrastructural examination revealed further features of mycorrhizal types: namely the shape of septal pores, presence and structure of matrix material in the region of the hyphal mantle and characteristic deposits on cell walls of the hyphae. The ten types presented can be distinguished without any ultrastructural features. As far as the fungal partners involved are concerned, basidiomycetes are clearly dominant. For the first time two basidiomycetes with continuous parenthesomes of their dolipores were found to form ectomycorrhizae. Classification of these fungi with the heterobasidiomycetes is discussed.

Identification of Picea-ectomycorrhizae by comparing DNA-sequences

Identification of the fungi forming ectomycorrhiza is still a great challenge. Ectomycorrhizae of Picea abies, collected in southwest Germany during several years and described as morphotypes, were identified using LSU and ITS sequences. To this the fungal sequences amplified from the mycorrhizae were compared with sequences from identified sporocarps. The fungal partner of Piceirhiza gelatinosa was identified as Hygrophorus olivaceoalbus, the fungal partner of Piceirhiza rosa-nigrescens was identified as Dermocybe cf. semisanguinea, and the fungal partner of a white mycorrhiza, described here for the first time, belongs to the Hebeloma velutipes group (Hebeloma crustuliniforme complex). Identification to genus level was possible for Piceirhiza lanuginosa where a Cortinarius-species is the fungal partner. A Tomentella-species forms a newly described light-brown mycorrhiza. Identification to family and to order-level was achieved for a milky-dull silvery mycorrhiza (Cortinariaceae), and Piceirhiza globulifera (Aphyllophorales), respectively. Ten samples of white, slightly bent mycorrhizae were formed by 8 different Cortinarius-species, including among others Cortinarius traganus, C. delibutus, and C. brunneus. The fungal partners of several brown, smooth mycorrhizae displaying only a Hartig net are Ascomycetes, among these are Wilcoxina cf. mikolae and Hymenoscyphus cf. ericae.

Structural characterization and molecular identification of arbuscular mycorrhiza morphotypes of Alzatea verticillata (Alzateaceae), a prominent tree in the tropical mountain rain forest of South Ecuador.

The vast majority of the highly diverse trees in the tropical mountain rain forest of South Ecuador form arbuscular mycorrhizas, and previous molecular investigations revealed a high diversity of fungi. In this study, we present a first trial to link fungal DNA-sequences with defined morphotypes characterized on the basis of partly new mycelial features obtained from field material of one tree species, Alzatea verticillata. Fine roots were halved lengthwise to study the mycelium anatomy on one half and to obtain fungal nuclear rDNA coding for the small subunit rRNA of Glomeromycota from the other half. Light microscopy revealed conspicuously large amounts of mycelium attaching to the surface of the rootlets. The mycelium formed fine- or large-branched appressoria-like plates, vesicles of regular or irregular shape, and very fine, multibranched structures ensheathed by septate hyphae. These previously undescribed features of the supraradical mycelia combined with intraradical mycelium structures were used for distinguishing of four main morphogroups and subordinate 14 morphotypes. DNA sequences of Glomus group A, Acaulospora and Gigaspora, were obtained and linked to three morphogroups. Two sequence types within Glomus group A could be tentatively associated to subordinate morphotypes.

Reforestation sites show similar and nested AMF communities to an adjacent pristine forest in a tropical mountain area of South Ecuador.

Arbuscular mycorrhizae are important for growth and survival of tropical trees. We studied the community of arbuscular mycorrhizal fungi in a tropical mountain rain forest and in neighbouring reforestation plots in the area of Reserva Biológica San Francisco (South Ecuador). The arbuscular mycorrhizal fungi were analysed with molecular methods sequencing part of the 18 S rDNA. The sequences were classified as Operational Taxonomic Units (OTUs). We found high fungal species richness with OTUs belonging to Glomerales, Diversisporales and Archaeosporales. Despite intensive sampling, the rarefaction curves are still unsaturated for the pristine forest and the reforestation plots. The communities consisted of few frequent and many rare species. No specific interactions are recognizable. The plant individuals are associated with one to ten arbuscular mycorrhizal fungi and mostly with one to four. The fungal compositions associated with single plant individuals show a great variability and variety within one plant species. Planted and naturally occurring plants show high similarities in their fungal communities. Pristine forest and reforestation plots showed similar richness, similar diversity and a significantly nested structure of plant-AMF community. The results indicate that small-scale fragmentation presently found in this area has not destroyed the natural AMF community, at least yet. Thus, the regeneration potential of natural forest vegetation at the tested sites is not inhibited by a lack of appropriate mycobionts.

Mycorrhiza Networks Promote Biodiversity and Stabilize the Tropical Mountain Rain Forest Ecosystem: Perspectives for Understanding Complex Communities

To better understand the mechanisms behind maintenance of the extraordinary plant and fungal diversity in tropical mountain forests we applied, for the first time, network theory to investigate the mycobiont–plant communities. We addressed three different mycorrhizal classes, arbuscular mycorrhizae of tropical trees, mycorrhizae of terrestrial and epiphytic Orchidaceae and cavendishioid mycorrhizae among Ericaceae and Sebacinales. We found significant nestedness (NODF) for arbuscular and orchid mycorrhizal networks. In accordance to previous simulations and verifications of species-rich, mutualistic plant–animal networks, we conclude that preferential attachment of new members to already existing links integrates and maintains rare species and stabilizes our species rich assemblages.

Two Lactarius species associated with a relict Fagus grandifolia var. mexicana population in a Mexican montane cloud forest

Ectomycorrhizal (EM) fleshy fungi are being monitored in a population of Fagus grandifolia var. mexicana persisting in a montane cloud forest refuge on a volcano in a subtropical region of central Veracruz (eastern Mexico). The population of Fagus studied represents one of the 10 recognized forest fragments still housing this tree genus in Mexico. This is the first attempt to document EM fungi associated with this tree species in Mexico. We present evidence of the ectomycorrhizal symbiosis for Lactarius badiopallescens and L. cinereus with this endemic tree. Species identification of Lactarius on Fagus grandifolia var. mexicana was based on the comparison of DNAsequences (ITS rDNA) of spatiotemporally co-occurring basidiomes and EM root tips. The host of the EM tips was identified by comparison of the large subunit of the ribulose-bisphosphate carboxylase gene (rbcL). The occurrence of Lactarius badiopallescens and L. cinereus populations in the area of study represent the southernmost record known to date of these two species in North America and are new for the Neotropical Lactarius mycota. Descriptions coupled with illustrations of macro- and micromorphological features of basidiomes as well as photographs of ectomycorrhizas are presented.

The mycorrhizal status of Taiwanese trees and the description of some ectomycorrhizal types

SummaryIn Taiwanese forests a dependence of mycorrhizal types on the altitude is recognizable: in the lower tropical regions VA-mycorrhizae dominate, whereas in the mixed subtropical forests most of the species show VA-mycorrhizae, but there are also several species with ectomycorrhizae. In the higher mountains ectomycorrhizae predominate. In addition to this relationship between mycorrhizal status and altitude, some tree species belong to typical ectomycorrhizal or VA-mycorrhizal families. Ten ectomycorrhizal types from Taiwanese trees were characterized by macroscopic, microscopic and ultrastructural features. The basic structures of hyphal mantles are the same in Taiwan as in the Black Forest (southwest Germany). Two of the types described and two further types are identical with types from the Black Forest on Picea abies (L.) Karst. Only two fungal partners could be identified (Lactarius, Amphinema), all others are unknown. Some noteworthy observations are: an epidermis-like covering of a hyphal mantle, an ectendomycorrhiza on Pinus taiwanensis Hayata with Amphinema byssoides and wall ingrowths in the outer cortical layer of Castanopsis-mycorrhizae.

A new species of Lactarius (subgenus Gerardii) from two relict Fagus grandifolia var. mexicana populations in Mexican montane cloud forests

A new milkcap species, Lactarius fuscomarginatus, was found in the subtropical region of central Veracruz (eastern Mexico) associated with two relict populations of Fagus grandifolia var. mexicana. The species is characterized macroscopically by its dark pileus and stipe and by its distant and whitish lamellae with blackish to blackish brown edges. A molecular phylogenetic analyses based on ITS and LSU nucDNA sequences confirms the delimitation of this new taxon and places L. fuscomarginatus in subgenus Gerardii. A detailed morphological comparison is given with similar species.