Kare Liimatainen

Improving ITS sequence data for identification of plant pathogenic fungi

SummaryPlant pathogenic fungi are a large and diverse assemblage of eukaryotes with substantial impacts on natural ecosystems and human endeavours. These taxa often have complex and poorly understood life cycles, lack observable, discriminatory morphological characters, and may not be amenable to in vitro culturing. As a result, species identification is frequently difficult. Molecular (DNA sequence) data have emerged as crucial information for the taxonomic identification of plant pathogenic fungi, with the nuclear ribosomal internal transcribed spacer (ITS) region being the most popular marker. However, international nucleotide sequence databases are accumulating numerous sequences of compromised or low-resolution taxonomic annotations and substandard technical quality, making their use in the molecular identification of plant pathogenic fungi problematic. Here we report on a concerted effort to identify high-quality reference sequences for various plant pathogenic fungi and to re-annotate incorrectly or insufficiently annotated public ITS sequences from these fungal lineages. A third objective was to enrich the sequences with geographical and ecological metadata. The results – a total of 31,954 changes – are incorporated in and made available through the UNITE database for molecular identification of fungi (http://unite.ut.ee), including standalone FASTA files of sequence data for local BLAST searches, use in the next-generation sequencing analysis platforms QIIME and mothur, and related applications. The present initiative is just a beginning to cover the wide spectrum of plant pathogenic fungi, and we invite all researchers with pertinent expertise to join the annotation effort.

EcM fungal community structure, but not diversity, altered in a Pb‐contaminated shooting range in a boreal coniferous forest site in Southern Finland

Boreal forests contain diverse fungal communities that form essential ectomycorrhizal symbioses with trees. To determine the effects of lead (Pb) contamination on ectomycorrhizal fungal communities associated with the dominant pine (Pinus sylvestris L.), we surveyed sporocarps for 3 years, analyzed morphotyped ectomycorrhizal root tips by direct sequencing, and 454-sequenced fungal communities that grew into in-growth bags during a 2-year incubation at a shooting range where sectors vary in the Pb load. We recorded a total of 32 ectomycorrhizal fungi that formed conspicuous sporocarps, 27 ectomycorrhizal fungal phylotypes from 294 root tips, and 116 ectomycorrhizal fungal operation taxonomic unit (OTUs) from a total of 8194 internal transcribed spacer-2 454 sequences. Our ordination analyses by nonparametric multidimensional scaling (NMS) indicated that the Pb enrichment induced a shift in the ectomycorrhizal community composition. This was visible as indicative trends in the sporocarp and root tip data sets, but was explicitly clear in the communities observed in the in-growth bags. The compositional shift in the ectomycorrhizal community was mainly attributable to an increase in the frequencies of OTUs assigned to genus Thelephora and to a decrease in the OTUs assigned to Pseudotomentella, Suillus, and Tylospora in Pb-contaminated areas when compared with the control. While the compositional shifts are clear, their functional consequences for the dominant trees or soil ecosystem function remain undetermined.

Cortinarius sect. Brunnei (Basidiomycota, Agaricales) in North Europe.

The section Brunnei was extensively studied based on material from North Europe. To stabilise the nomenclature we studied the relevant types of taxa included in this section. Phylogenetic relationships and species limits were investigated using rDNA ITS sequences and the results were compared with the morphological data. We recognised 11 species: Cortinarius brunneus, C. clarobrunneus comb. nov., C. coleoptera, C. ectypus, C. gentilis, C. glandicolor (neotypified), C. pseudorubricosus, and four species described as new C. caesiobrunneus, C. albogaudis, C. carabus, and C. cicindela. They are described here and their taxonomy, ecology, distribution, and relationships are discussed. In addition, a key to species of the section Brunnei is provided. A total of 77 new sequences of 11 species are published including nine type sequences. Also the taxonomic assignments of sequences in the public databases belonging to the section Brunnei are revised.

The largest type study of Agaricales species to date: bringing identification and nomenclature of Phlegmacium (Cortinarius) into the DNA era

Cortinarius is a species-rich and morphologically challenging genus with a cosmopolitan distribution. Many names have not been used consistently and in some instances the same species has been described two or more times under separate names. This study focuses on subg. Phlegmacium as traditionally defined and includes species from boreal and temperate areas of the northern hemisphere. Our goals for this project were to: i) study type material to determine which species already have been described; ii) stabilize the use of Friesian and other older names by choosing a neo- or epitype; iii) describe new species that were discovered during the process of studying specimens; and iv) establish an accurate ITS barcoding database for Phlegmacium species. A total of 236 types representing 154 species were studied. Of these 114 species are described only once whereas 40 species had one ore more synonyms. Of the names studied only 61 were currently represented in GenBank. Neotypes are proposed for 21 species, and epitypes are designated for three species. In addition, 20 new species are described and six new combinations made. As a consequence ITS barcodes for 175 Cortinarius species are released.

Cortinarius sect. Armillati in northern Europe

Cortinarius sect. Armillati (subgenus Telamonia) was studied extensively based on morphology and molecular data. A total of about 1000 specimens, mostly from Fennoscandia, were revised. The nomenclature of the species was confirmed by sequencing the type material. Phylogenetic relationships were inferred by analyses of ITS, and the results were compared with the morphological and ecological data. Based on macro- and micromorphological characters, as well as molecular data, section Armillati contains only the medium to large species with slightly hygrophanous pileus and ± reddish or in some species yellowish brown to rose brown universal veils. The other red-brown-veiled species, previously included in Armillati, seem to belong to at least seven different sections or clades: sect. Anthracini, sect. Boulderenses, sect. Brunneotincti p.p., sect. Cinnabarini, sect. Fulvescentes, /Fuscoperonatus, and /Praestigiosus. Our study recognized six Armillati species from northern Europe: C. armillatus, C. luteo-ornatus, C. paragaudis, and three species described as new, C. pinigaudis, C. roseoarmillatus, and C. suboenochelis. The former three also occur in North America. Two additional species, C. subarmillatus (Japan) and C. quercoarmillatus (Costa Rica), are known outside the area. Based on the phylogenetic analysis, the species associated with deciduous trees, C. armillatus, C. quercoarmillatus, and C. roseoarmillatus, all with dextrinoid, thick-walled spores, formed a separate group from the mainly conifer-associated species, C. luteo-ornatus, C. paragaudis, C. pinigaudis and C. suboenochelis, all with fairly thin to moderately thick-walled, indextrinoid to moderately dextrinoid spores. Descriptions of the northern European species are provided, the distribution is mapped and their taxonomy, ecology, distribution, and relationships are discussed. A total of 64 new sequences of 12 species are reported including 17 sequences from type material. Our study also suggests that ITS sequences are not always sufficiently variable for species-rank recognition (barcoding) in Cortinarius.

Determining threshold values for barcoding fungi: lessons from Cortinarius (Basidiomycota), a highly diverse and widespread ectomycorrhizal genus

Different distance-based threshold selection approaches were used to assess and compare use of the internal transcribed spacer (ITS) region to distinguish among 901 Cortinarius species represented by >3000 collections. Sources of error associated with genetic markers and selection approaches were explored and evaluated using MOTUs from genus and lineage based-alignments. Our study indicates that 1%-2% more species can be distinguished by using the full-length ITS barcode as compared to either the ITS1 or ITS2 regions alone. Optimal threshold values for different picking approaches and genetic marker lengths inferred from a subset of species containing major lineages ranged from 97.0% to 99.5% sequence similarity using clustering optimization and UNITE SH, and from 1% to 2% sequence dissimilarity with CROP. Errors for the optimal cutoff ranged from 0% to 70%, and these can be reduced to a maximum of 22% when excluding species lacking a barcode gap. A threshold value of 99% is suitable for distinguishing species in the majority of lineages in the genus using the entire ITS region but only 90% of the species could be identified using just the ITS1 or ITS2 region. Prior identification of species, lacking barcode gaps and their subsequent separate analyses, maximized the accuracy of threshold approaches.

Cortinarius section Sanguinei in North America

The North American species of Cortinarius section Sanguinei were studied using morphological characters and ITS and RPB2 sequence data. Several type collections also were examined. Four species were identified: C. harrisonii sp. nov, C. neosanguineus sp. nov., C. sanguineus and C. sierraensis comb. nov. Of these, C. sanguineus also occurs in Europe together with C. puniceus, a fifth member of the section. Typical features of these species include ± red, fairly small basidiomata, stipe basal mycelium often with yellow to reddish yellow tints, amygdaloid to ellipsoid spores, and aniline-red lamellar trama and pileipellis hyphae when mounted in KOH. Two other species with red lamellae C. marylandensis comb. nov. and C. smithii stat. nov. & nom. nov. also are discussed.

Cortinarius sanguineus and equally red species in Europe with an emphasis on northern European material

The red species of Cortinarius subgenus Dermocybe in Europe were studied based on morphological and molecular data. Three completely red species were recognized: C. sanguineus (syn. C. sanguineus var. aurantiovaginatus), C. puniceus (syn. C. cruentus, C. rubrosanguineus) and C. vitiosus comb. nov. Cortinarius sanguineus has dusky red to red pileus, reddish yellow mycelium and lacking or with only slightly encrusted hyphae in pileipellis. It occurs in mesic to damp forests with Picea, often on rich soil in the boreal and montane areas of Europe, presumably also in eastern Canada. Cortinarius puniceus differs from C. sanguineus by its stronger purplish red, narrower spores and spot-like encrusted hyphae in pileipellis. It grows with deciduous trees in the temperate zone of Europe. Cortinarius vitiosus is known only from Fennoscandia and occurs in dry to mesic coniferous forests. It has fairly thin, often zonate, dark red to dark reddish brown pileus, pale red mycelium, small spores and encrusted lamellar trama and pileipellis hyphae. In addition to these three species C. fervidus and C. phoeniceus occasionally have red basidiomes. The relationships of the species were inferred by analysis of ITS sequences. Our study suggests that the section Sanguinei, as earlier defined, is polyphyletic. Here the section is limited to include C. sanguineus, C. puniceus and North American D. sierraensis. The relationships with other red species were not determined. Section Dermocybe, including C. cinnamomeus, C. croceus and C. uliginosus, formed a monophyletic group, and the section Malicoriae had some support. A total of 34 new sequences are published including nine from type specimens.

Two new species in Cortinarius subgenus Telamonia, Cortinarius brunneifolius and C. leiocastaneus, from Fennoscandia (Basidiomycota, Agaricales)

Two new Cortinarius species, C. brunneifolius and C. leiocastaneus, are described based on molecular and morphological data. Cortinarius brunneifolius looks like a trivial brown Telamonia. It is characterised by the fairly dark brown cap and gills contrasting with the white stem. The major distinctive features are the refracting, colourless granules in the epicutis hyphae, broadly ellipsoid, equally verrucose spores, and fruitbody without bluish tints. Cortinarius leiocastaneus can be fairly easily recognised by the appearance of miniature brown Telamonia species, narrowly amygdaloid spores, and a habitat with Betula. Detailed descriptions of the species are provided as well as comparisons with macro- and microscopically similar existing telamonioid taxa. Phylogenetic relationships within the genus were studied by use of ITS rDNA sequence data. Ten new ITS sequences are published. Cortinarius brunneifolius and C. leiocastaneus are fairly closely related and belong to the subgenus Telamonia sensu stricto. The infrasubgeneric relationships were not well resolved, but the new species seem to be unrelated to the macroscopically similar species and do not clearly belong to any of the existing sections.

Two new species of Cortinarius, subgenus Telamonia, sections Colymbadini and Uracei, from Europe

Two new Cortinarius species are described from European Quercus forests and one new combination is made based on molecular and morphological data. Cortinarius uraceomajalis is a vernal species currently only known from Hungary, Bulgaria and Italy, but likely is common throughout central and south-eastern Europe. Cortinarius uraceonemoralis is a widely distributed species in Europe. The new combination Cortinarius nolaneiformis is based on Hydrocybe nolaneiformis Velen. and is a widespread vernal species in Europe. Cortinarius uraceomajalis and C. nolaneiformis are preliminarily placed in sect. Colymbadini, characterized by having a positive (yellow) UV reaction, while C. uraceonemoralis with a UV negative reaction is placed in sect. Uracei. A neotype is selected for C. colymbadinus and C. uraceus to stabilize the nomenclature. Taxonomic novelties: Cortinarius uraceomajalis Dima, Liimat., Niskanen & Bojantchev, Cortinarius uraceonemoralis Niskanen, Liimat., Dima, Kytöv., Bojantchev & H. Lindstr., Cortinarius nolaneiformis (Velen.) Dima, Niskanen & Liimat.