Two new genera, Dominikia and Kamienskia, and D. disticha sp. nov. in Glomeromycota

Two new genera, Dominikia and Kamienskia, with five species originally described as Glomus achrum, G. bistratum, G. iranicum, G. minutum and G. perpusillum and two undescribed fungi, D. disticha sp. nov. and D. 211-1 sp. ined., were erected based on morphological studies of spores and mycorrhizal structures and phylogenetic analyses of sequences spanning the small subunit (SSU, partial) nuclear ribosomal RNA gene (nrDNA), the internal transcribed spacer (ITS1, 5.8S, ITS2, full) and the large subunit (LSU, partial) nrDNA. Glomus bistratum and G. perpusillum formed the genus Kamienskia, and the other species were transferred to Dominikia. The main feature linking the seven species is production of hyaline or pale-coloured, small spores in clusters that were not found in field-collected soils to date. Spores of D. disticha are hyaline, globose to subglobose, (28-)40(-57) µm diam., rarely egg-shaped to prolate, 29-34 × 36-52 µm and have a single subtending hypha. The spore wall of D. disticha consists of three hyaline layers: a mucilaginous, short-lived layer 1, forming the spore surface, which stains in Melzer's reagent, a laminate layer 2 and a flexible to semi-flexible layer 3. The subtending hypha is cylindrical to funnel-shaped. D. disticha was found associated with roots of Thinopyrum distichum colonizing maritime sand dunes of the Reserve Rooiels, South Africa, and this is the only site of its occurrence known to date.