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Although the Caucasus region belongs to the world biodiversity hotspots, arbuscular mycorrhizal fungi (AMF) have not been investigated in this area. A total of 11 mixtures of soils and roots from 11 localities in southern Georgia in an altitudinal gradient from 1 to 1560 m a. s. l. were sampled in 2015. AMF spores and arbuscular mycorrhiza were observed in all samples. Eight AMF species were found in the field-collected soils: Acaulospora bireticulata, Acaulospora cavernata, Funneliformis coronatum, Gigaspora gigantea, Glomus rubiforme, Scutellospora dipurpurescens, Septoglomus constrictum, and Septoglomus jasnowskae. The most frequently occurring species proved to be S. constrictum. Laboratory cultures with soil-root mixtures revealed 4 species of AMF that were not found in the field-collected soils: Glomus macrocarpum, Entrophospora infrequens, Claroideoglomus claroideum, and Funneliformis mosseae. The overall spore abundance of AMF in 50 g of dry soil/substrate averaged 130 and 1.3 in the field and in the laboratory cultures, respectively. This is the first report concerning AMF species diversity and AMF root colonization in Georgia. To our knowledge, mycorrhizal status of Linum nervosum , Ranunculus illyricus, Stipa arabica, Veronica minuta and Vinca herbacea was given for the first time. Further studies are necessary in this region of Asia.

A new arbuscular mycorrhizal fungal species of genus Glomus, G. perpusillum(Glomeromycota), forming small, hyaline spores is described and illustrated. Spores of G. perpusillumwere formed in hypogeous aggregates and occasionally inside roots. They are globose to subglobose, (10–)24(–30) μm diam, rarely egg-shaped, oblong to irregular, 18–25 × 25–63 μm. The single spore wall of G. perpusillumconsists of two permanent layers: a finely laminate, semiflexible to rigid outer layer and a flexible to semiflexible inner layer. The inner layer becomes plastic and frequently contracts in spores crushed in PVLG-based mountants and stains reddish white to grayish red in Melzer’s reagent. Glomus perpusillumwas associated with roots of Ammophila arenariacolonizing sand dunes of the Mediterranean Sea adjacent to Calambrone, Italy, and this is the only site of its occurrence known to date. In single-species cultures with Plantago lanceolataas host plant, G. perpusillumformed vesicular-arbuscular mycorrhiza. Phylogenetic analyses of partial SSU sequences of nrDNA placed the species in Glomusgroup A with no affinity to its subgroups. The sequences of G. perpusillumunambiguously separated from the sequences of described Glomusspecies and formed a distinct clade together with in planta arbuscular mycorrhizal fungal sequences found in alpine plants.

Systematics of arbuscular mycorrhizal fungi have been unraveled in recent years based on molecular phylogenies. Here we report on analyses of the internal transcribed spacer and of the small and large nuclear ribosomal gene sequences (ITS, SSU and LSU) of spores of Glomus laccatum that place this species in the genus Paraglomus of the family Paraglomeraceae, phylum Glomeromycota. Consequently, we recombine G. laccatum as Paraglomus laccatum. Morphological characters of spores and mycorrhizae coming from one-species cultures of this fungus are illustrated and presented in the emended description.

The morphological features of spores of Glomus pustulatum found in Poland are described and illustrated, and the worldwide occurrence of this species is characterized. Spores of G. pustulatum from Poland do not differ from those originally found in Canada and the United States of America. They were found in only one of more than 300 soil samples taken from over 100 localities in Poland. G. pustulatum was associated with roots of Ammophila arenaria colonizing maritime sand dunes of the Slowinski National Park, with a mean spore density of 12 in 100?g dry soil. Associated species of G. pustulatum were Acaulospora dilatata and Scutellospora dipurpurascens. G. pustulatum was found in Poland for the first time and is probably a species new to Europe.

Spores of Acaulospora dilatataand Scutellospora dipurpurascensfound in Poland are described and illustrated and their occurrence and distribution are characterized and mapped. Spores of Acaulospora dilatatafrom Poland do not differ from those originally described in the United States of America. The germination shield found in a number of spores is described and illustrated, and compared with that occurring in members of the genus Scutellospora. Acaulospora dilatatawas found in five of the 303 soil samples taken from around the roots of Ammophila arenariacolonizing maritime sand dunes of the Slowinski National Park. Polish specimens of S. dipurpurascensare similar in size, wall structure, and reaction in Melzer’s reagent to those described from the type localized in the United States of America. However, some spores from Poland have a thicker wall, greater sporogenous cells, and are somewhat darker coloured. They were recovered from 34 soils sampled from forests, gardens, sand dunes, and both cultivated and uncultivated soils. S. dipurpurascenswas commonly associated with different plants of the Hel Peninsula and occurred regularly among the roots of Ammophila arenariagrowing in the Slowinski National Park. Both species were found for the first time in Poland and are probably new to Europe.