Gerard Chwat

Three new species of arbuscular mycorrhizal fungi discovered at one location in a desert of Oman: Diversispora omaniana, Septoglomus nakheelum and Rhizophagus arabicus

Three new species of arbuscular mycorrhizal (AM) fungi (Glomeromycota) were isolated from soil samples collected from a hyperarid sandy plain of South Arabia. Morphological characteristics of the spores clearly differentiated them from closely related AM species. Molecular analyses were performed on rDNA sequences obtained from single spores including a ~1700 bp region comprising partial SSU, ITS, partial LSU and the ~600 bp ITS region only. The phylogenetic trees based on these regions showed that the three species belong to well described genera but are clearly distinct from known species. Consequently, we describe them here as Diversispora omaniana, Septoglomus nakheelum and Rhizophagus arabicus spp. nov. D. omaniana and R. arabicus were isolated from the native, arid habitat, while S. nakheelum was isolated from a nearby irrigated date palm plantation. The discovery of three new species of AM fungi from this location suggests that a number of additional undescribed AM taxa may be present in such desert ecosystems. Further work to understand the diversity and functional significance of these new AM taxa may offer new opportunities for conservation, re-vegetation, and sustainable agriculture in extremely arid environments.

Septoglomus fuscum and S. furcatum, two new species of arbuscular mycorrhizal fungi (Glomeromycota)

Two new arbuscular mycorrhizal fungal species, (Glomeromycota) Septoglomus fuscum and S. furcatum, are described and illustrated. Spores of S. fuscum usually occur in loose hypogeous clusters, rarely singly in soil or inside roots, and S. furcatum forms only single spores in soil. Spores of S. fuscum are brownish orange to dark brown, globose to subglobose, (20–)47(–90) μm diam, rarely ovoid, 21–50 × 23–60 μm. Their spore wall consists of a semi-persistent, semi-flexible, orange white to golden yellow, rarely hyaline, outer layer, easily separating from a laminate, smooth, brownish orange to dark brown inner layer. Spores of S. furcatum are reddish brown to dark brown, globose to subglobose, (106–) 138(–167) μm diam, rarely ovoid, 108–127 × 135–160 μm, usually with one subtending hypha that is frequently branched below the spore base, or occasionally with two subtending hyphae located close together. Spore walls consists of a semipermanent, hyaline to light orange outermost layer, a semipermanent, hyaline to golden yellow middle layer, and a laminate, smooth, reddish brown to dark brown innermost layer. None of the spore-wall layers of S. fuscum and S. furcatum stain in Melzer’s reagent. In the field, S. fuscum was associated with roots of Arctotheca populifolia colonizing maritime dunes located near Strand in South Africa and S. furcatum was associated with Cordia oncocalyx growing in a dry forest in the Ceará State, Brazil. In single-species cultures with Plantago lanceolata as host plant, S. fuscum and S. furcatum formed arbuscular mycorrhizae. Phylogenetic analyses of the SSU, ITS and LSU nrDNA sequences placed the two new species in genus Septoglomus and both new taxa were separated from described Septoglomus species.

Septoglomus jasnowskae and Septoglomus turnauae, two new species of arbuscular mycorrhizal fungi (Glomeromycota)

Phylogenetic analyses of SSU-ITS-LSU nrDNA sequences and morphological studies of spores and mycorrhizae confirmed our supposition of finding two new species of arbuscular mycorrhizal fungi of the genus Septoglomus in the phylum Glomeromycota. Morphologically, the first species, named S. jasnowskae, is distinguished by its pale yellow to brownish yellow, small spores with a 2-layered spore wall, of which the colourless outer layer 1 stains dark in Melzer’s reagent and layer 2 is laminate. The spores usually arise in loose clusters. The structures most distinguishing S. turnauae are its two coloured laminate layers in the 4-layered spore wall. In the field S. jasnowskae was associated with roots of Ammophila arenaria and an unrecognized plant species colonizing maritime dunes of the Mediterranean Sea near Thessalonica (Greece) and Calella (Spain), respectively, and S. turnauae formed mycorrhiza with a Cistus sp. (Cistaceae) growing in the soil of a mine located in Sulcis-Iglesiente, SW-Sardinia, Italy. In single-species cultures with Plantago lanceolata as host plant, the mycorrhiza of S. jasnowskae consisted of arbuscules, hyphae and vesicles, and that of S. turnauae comprised arbuscules and hyphae only.

Spore-based study of arbuscular mycorrhizal fungi of semiarid sandy areas in Hungary, with Diversispora jakucsiae sp. nov.

We studied the diversity of arbuscular mycorrhizal fungi (AMF) in semiarid sandy areas of the Great Hungarian Plain representing the westernmost of the Eurasian steppe belt. AM fungal spores were extracted (i) directly from soils collected around 30 Juniperus communis trees of three sampling sites and (ii) from pot trap cultures established with soils from those samples. Altogether spores of 31 AMF species belonging to 15 genera were identified from the field and pot-culture samples. Three taxa could be identified only on the genus level. During the study, one fungus showed a unique combination of morphological characters. Molecular phylogenetic analyses of SSU, ITS, and LSU regions of the nrDNA positioned the fungus in the genus Diversipora and confirmed its novelty when compared with all Diversipora spp. species sequenced to date. This fungus is here described as D. jakucsiae sp. nov.

Three new arbuscular mycorrhizal Diversispora species in Glomeromycota

Morphological observations of spores and mycorrhizal structures of three arbuscular mycorrhizal fungi (Glomeromycota) prompted, and subsequent phylogenetic analyses of SSU–ITS–LSU nrDNA sequences confirmed, that they are undescribed species of the genus Diversispora. Morphologically, the first species, here named D. varaderana, is most distinguished by its relatively small (≤90 μm diam when globose) and yellow-coloured spores with a simple spore wall consisting of two layers, of which layer 1, forming the spore surface, is short-lived and usually completely sloughed in most spores. The distinctive features of the second species, D. peridiata, are the occasional formation of spores in clusters and peridium-like hyphae covering the clusters and single spores, and especially the permanent and relatively thick spore wall layer 1, which is the only coloured component of the two-layered spore wall of the yellow-coloured and relatively small spores (≤100 μm diam). The third species, D. slowinskiensis, is most characterized by its spore wall layer 1 that is the only coloured component of the three-layered spore wall and frequently is covered with blister-like swellings. All the three species were grown in single-species cultures established from spores extracted from trap cultures inoculated with rhizosphere soils of plants growing in maritime sand dunes: D. varaderana from those located near Varadero on the Hicacos Peninsula, Cuba, and the two others from those of the Słowiński National Park, northern Poland.

Sacculospora felinovii, a novel arbuscular mycorrhizal fungal species (Glomeromycota) from dunes on the west coast of India

During an arbuscular mycorrhiza fungal spore survey on a primary coastal sand-dune system in Goa on the west coast of India, entrophosporoid spores tightly covered with a dense hyphal mantle were recovered. When intact, the spores, at first sight, seemed to be identical in morphology to those of Sacculospora baltica (originally described as Entrophospora baltica) extracted from Polish maritime sand dunes and, to date, the sole member of the recently described genus Sacculospora in the new family Sacculosporaceae, phylum Glomeromycota. Later detailed morphological studies indicated that both fungi produce two-walled spores but the structure and phenotypic features of components of the outer spore wall in the novel fungus differ considerably from those of S. baltica. Differences between the fungi were subsequently confirmed in the phylogenetic analysis of SSU–ITS–LSU nrDNA sequences. Consequently, we describe the novel species as Sacculospora felinoviisp. nov.