No abstract

The mycobionts of Piceirhiza bicolorata, a distinct ectomycorrhizal morphotype of conifers and hardwoods, have been identified by internal transcribed spacer 1 (ITS1) nuclear ribosomal DNA (rDNA) sequence comparison of the fungi involved. Samples of Piceirhiza bicolorata were obtained from seedlings of Picea abies, Pinus sylvestris, Betula pubescens, Populus tremula, Quercus robur and Salix phylicifolia. In an initial screening, the fungus amplified with universal ITS primers from ectomycorrhizal root samples of P. bicolorata shared approx. 95% ITS1 sequence identity with the ericoid mycorrhizal fungus Hymenoscyphus ericae. A total of 77 out of 88 (l 87.5%) DNA samples (i.e. 52\56 root samples and 25\32 axenic culture isolates) of P. bicolorata were successfully amplified with a taxon-selective primer designed for exclusive amplification of H. ericae-like strains. Forty-seven amplicons were sequenced, yielding 15 different ITS1 genotypes that differed by 1-14 nucleotide character state changes. An inferred ITS1 phylogeny (maximum parsimony) showed that a single major evolutionary lineage of P. bicolorata embraced the historically important H. ericae isolates in a 100% bootstrap-supported clade. The 15 P. bicolorata genotypes were positioned in four subclades, roughly corresponding to morphological groups of P. bicolorata isolates observed in axenic culture. Culture isolates of H. ericae and P. bicolorata share some common morphological features including slow, dense growth and formation of short aerial hyphal aggregates. Our results suggest that members of the H. ericae aggregate participate in the formation of the distinct ectomycorrhizal morphotype P. bicolorata. This opposes the widely accepted discrimination of ericoid and ectomycorrhizal mycobionts of the boreal forest ecosystem. The high prevalence of the P. bicolorata morphotype on pioneer seedlings of P. sylvestris, B. pubescens and S. phylicifolia at a copper mine spoil was remarkable. Hypotheses of possible nutrient mobilization and detoxification potentials of the fungal associates of P. bicolorata are discussed. We hypothesize that ericoid and ectomycorrhizal plants may share mycobionts of the H. ericae aggregate.

Summary• The diversity and phylogenetic affinities of symbiotic root-associated ascomycetes of the Helotiales are reported here based on ITS1-5.8S-ITS2 (internal transcribed spacer, ITS) nrDNA sequences.• Mycobionts were obtained from roots of ericoid plants and grasses and from Piceirhiza bicolorata ectomycorrhizas (pbECM) on conifers and hardwoods, predominantly in burnt and metal-polluted habitats. The mycobionts were sequenced through the ITS and compared with sequences of known helotialean taxa.• We recognized 132 fungal ITS-sequences with affinity to the Helotiales, of which 75% (54 different ITS-genotypes) grouped within the Hymenoscyphus ericae aggregate including Phialophora finlandia. This aggregate showed stronger affinity to members of the Hyaloscyphaceae and Dermateaceae than to Hymenoscyphus fructigenus (genus-type species; Helotiaceae). Most of the pbECM mycobionts grouped with P. finlandia, although some grouped with H. ericae. Two genotypes co-occurred in ericoid and ectomycorrhizal roots.• The H. ericae aggregate may be referable to a generic unit, and includes a diverse group of closely related, more or less darkly pigmented, root-associated ascomycetes where the borders between intra-and interspecific ITS-sequence variation, as well as different mycorrhizal and nonmycorrhizal root-symbioses, remains unclear.

Helvella is a widespread, speciose genus of large apothecial ascomycetes (Pezizomycete: Pezizales) that are found in terrestrial biomes of the Northern and Southern Hemispheres. This study represents a beginning on assessing species limits and applying correct names for Helvella species based on type material and specimens in the university herbaria (fungaria) of Copenhagen (C), Harvard (FH) and Oslo (O). We use morphology and phylogenetic evidence from four loci – heat shock protein 90 (hsp), translation elongation factor alpha (tef), RNA polymerase II (rpb2) and the nuclear large subunit ribosomal DNA (LSU) – to assess species boundaries in an expanded sample of Helvella specimens from Europe. We combine the morphological and phylogenetic information from 55 Helvella species from Europe with a small sample of Helvella species from other regions of the world. Little intraspecific variation was detected within the species using these molecular markers; hsp and rpb2 markers provided useful barcodes for species delimitation in this genus, while LSU provided more variable resolution among the pertinent species. We discuss typification issues and identify molecular characteristics for 55 European Helvella species, designate neo- and epitypes for 30 species, and describe seven Helvella species new to science, i.e., H. alpicola, H. alpina, H. carnosa, H. danica, H. nannfeldtii, H. pubescens and H. scyphoides.

No abstract