Arbuscular mycorrhizal fungi in Georgia, the Caucasus region: the first report of species diversity and root colonization

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.