Glomus perpusillum, a new arbuscular mycorrhizal fungus

A new arbuscular mycorrhizal fungal species of genus Glomus, G. perpusillum (Glomeromycota) I forming small, hyaline spores is described and illustrated. Spores of G. perpusillum. were formed ill hypogeous aggregates and occasionally inside roots. They are globose to subglobose, (10-)24(-30) pin diam, rarely egg-shaped, oblong to irregular, 18-25 X 25-63 mu m. The single spore wall of G. perpusillum, consists 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 perpusillum. was associated with roots of Ammophila arenaria, colonizing 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 lanceolata as host plant, G. perpusillum formed vesicular-arbuscular mycorrhiza. Phylogenetic analyses of partial SSU sequences of nrDNA placed the species in Glomus group A with no affinity to its subgroups. The sequences of G. perpusillum unambiguously separated from the sequences of described Glomus species and formed a distinct clade together with in planta arbuscular mycorrhizal fungal sequences found in alpine plants.