| Dark septate endophytes (DSE) were obtained from the roots of 90 healthy aspen saplings, which were five to seven years old and from five different sites in central Alberta where soils were either chernozem or luvisol and either wet or dry. DSE were isolated in pure culture and then identified using cultural and morphological characteristics, along with rDNA sequence analyses. Six taxa were identified including Cryptosporiopsis ericae, C. radicicola, Leptodontidium orchidicola, Phialocephala fortinii, Cadophora spp. and Exophiala sp. Distribution patterns according to soil type and moisture were inconclusive although C. ericae was isolated most frequently from dry soils, and L. orchidicola was isolated most frequently from luvisol. When isolates of C. ericae and C. radicicola were inoculated onto axenically grown aspen seedlings, their colonization patterns in roots, as determined by light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were distinct. Cryptosporiopsis ericae was restricted to the epidermis but C. radicicola penetrated deeper into the cells of the root cortex. All six species of Cryptosporiopsis known to inhabit roots (C. brunnea, C. ericae, C. grisea, C. melanigena, C. radicicola, and C. rhizophila) were compared in a culture-based study using LM and SEM to determine stable characters that could be used to build a key to improve routine identification procedures. Most species could be distinguished according to conidiomatal features. An isolate resembling common DSE species, P. fortinii, and obtained from a contaminated heparin solution in Missouri, was described as the new species, Phialocephala urceolata. |
