[Show abstract][Hide abstract] ABSTRACT: Using a heat treatment method, two genera of heat resistant and xerotolerant basidiomycetes were isolated from soil samples. These two genera, Basidioascus and Geminibasidium gen. nov., are morphologically similar and phylogenetically related. The genus Basidioascus was originally described as an ascomycete but the structures originally interpreted as single-spored asci appear to represent basidiospores. Morphologically, both genera are characterized by the lack of a fruiting body, conspicuously granular and deciduous basidia with a unique basal lateral projection, and apparently double walled basidiospores. The basidia, rather than the basidiospores, are forcibly discharged in Basidioascus species but not in Geminibasidium species. In Geminibasidium species, a putative basidium arises from a primary cell. These are novel forms of basidial ontogenesis previously unseen in basidiomycetes. The rDNA (SSU+5.8S+LSU) Bayesian phylogenetic analysis suggests that these fungi are distantly related to Wallemia, another xerotolerant basidiomycete genus commonly found in indoor air dust, dried foods and natural hypersaline environments. Given the physiological similarity and phylogenetic relationships, Basidioascus and Geminibasidium are classified in a new order, Geminibasidiales, and are taxonomically assigned to the class Wallemiomycetes. Based on morphological observations and molecular phylogeny of the internal transcribed spacer (ITS), two species of Basidioascus (B. undulatus and B. magus sp. nov.) and two species of Geminibasidium (G. donsium sp. nov. and G. hirsutum sp. nov.) are described. A key to these species is provided using micromorphological and cultural characters.
[Show abstract][Hide abstract] ABSTRACT: Three new species of heat-resistant fungi related to the hyphomycete Cladosporium staurophorum (Kendrick) M.B. Ellis were isolated from heat-treated soil from commercial lowbush blueberry fields and other sites in eastern Canada. Cladosporium staurophorum and the three new species produce characteristic dark, multicelled chlamy dospores. Phylogenetic analysis of nuclear ribosomal internal transcribed spacer DNA sequences suggest that these four species form a monophyletic group that is marginal in the Mycosphaerellaceae and phylogenetically distinct from Cladosporium sensu stricto. The new genus Devriesia is described for C. staurophorum, the three new species, and a fifth species originally described as Cladosporium chlamydosporis. A key to distinguish the five accepted species is provided. The species of the genus are dimorphic and share similar cladosporium-like conidial anamorphs consisting of pale brown, short, acropetally produced chains of cylindrical to fusiform, zero- or one-septate conidia and ramoconidia, diagnostic chlamydosporic synanamorphs, and a soil-borne, heat-resistant ecology. Devriesia acadiensis N.L. Nickerson & Seifert, with clover-shaped chlamydospores, Devriesia shelburniensis N.L. Nickerson & Seifert, with large, multi celled chlamydospores, and Devriesia thermodurans N.L. Nickerson & Seifert, with few-celled, clavate chlamy dospores, are described as new species. Chlamydospores from cultures of D. acadiensis, Devriesia staurophora, and D. thermodurans germinated after exposure to 75 °C for 30 min. Germination of these spores was activated by a heat shock. Chlamydospores from cultures of C. shelburniensis did not germinate after heat exposure.Key words: dematiaceous hyphomycetes, heat-resistant fungi, lowbush blueberries, Vaccinium angustifolium, ITS rDNA phylogeny.
Canadian Journal of Botany 02/2011; 82(7):914-926. · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The new anamorph genus Leohumicola (hyphomycetes) is described for four species, including three new species isolated after heat treatment of soils collected in Canada. The species produce slow-growing agar colonies that eventually produce lateral or terminal aleurioconidia, with a dark brown terminal cell, and the remains of a paler basal cell that fractures during secession. The genus is compared with Humicola, Trichocladium, Thermomyces, Complexipes and some other morphologically similar genera. Nuclear ribosomal small subunit (SSU) ribosomal DNA sequences demonstrate that Leohumicola is a monophyletic group in the Leotiomycetes, distinct from Humicola and Trichocladium (Sordariales), and Thermomyces (Eurotiales). Internal transcribed spacer sequences (ITS) support our recognition of four species of Leohumicola, each with distinct colony and micromorphological characters. The existence of additional species is probable based on our own ITS sequences and some retrieved from GenBank. The type species L. verrucosa, was recovered from a variety of soil types across Canada, and has sympodially proliferating conidiogenous cells that produce conidia with verrucose terminal cells that measure 4–5.5 x 4–5.5 µm. The SSU of some strains of this species have five long Group I introns that extend the length to more than 3700 nt. Leohumicola lenta produces very slowly growing colonies on agar media and larger conidia than L. verrucosa, and L. terminalis produces only terminal conidia. The latter two species are represented by single strains. The fourth species, L. minima is based on Trichocladium minimum, originally isolated from volcanic ash soil from Chile. Internal transcribed specer (ITS) sequences suggest that Humicola is a synonym of Trichocladium, a finding that may require conservation of Humicola. Dichotomous keys are provided to the accepted species of Leohumicola, and to morphologically similar aleurioconidial genera.
[Show abstract][Hide abstract] ABSTRACT: Paratritirachium is a recently described, monotypic, basidiomycete genus in the Pucciniomycotina with one described asexual species, P. cylindroconium. Three strains of an undescribed species of Paratritirachium were isolated from flare pit soils from Alberta, Canada, using a heat treatment method. Both asexual and sexual propagules were produced in culture. Asexual reproduction was characterized by unbranched or sparingly branched conidiophores and sympodial, slightly vesicular conidiogenous cells producing aseptate conidia. Distinctive curved basidia were commonly produced in culture, yielding two pale brown, thick-walled and oval basidiospores. The basidiospores were heat-resistant and germinated only when exposed to heat. Phylogenetic analyses using the internal transcribed spacer (ITS) region and the combined small and large ribosomal subunits confirmed that these isolates are a new species of Paratritirachium, described in this study as P. curvibasidium, and that Paratritirachium should be classified in the class Tritirachiomycetes, order Tritirachiales, and family Tritirachiaceae. Transmission electron microscopy revealed simple, uniperforate septa, similar to those of a Tritirachium species, supporting the placement of Paratritirachium in the class Tritirachiomycetes. This study provides the first description of sexual reproduction in the Tritirachiomycetes and the first report of basidiospore germination after heat treatment at a high temperature (75 °C).