Acaulospora ignota and Claroideoglomus hanlinii, two new species of arbuscular mycorrhizal fungi (Glomeromycota) from Brazil and Cuba

Morphological studies of spores and mycorrhizal structures and phylogenetic analyses of sequences of the partial small subunit rRNA gene, the whole internal transcribed spacer rDNA region, including the 5.8S rRNA gene, and the partial large subunit rRNA gene of two arbuscular mycorrhizal fungi (Glomeromycota) have indicated that they are undescribed species, one of the genus Acaulospora and the second of Claroideoglomus. The first species, here named A. ignota, is distinguished morphologically by yellow-coloured, relatively small (65–80 μm diam when globose) spores, whose upper surface of the structural laminate spore wall layer is ornamented with inconspicuous warts or flattened elevations, usually deteriorating and disappearing with age. The most distinguishing features of the second species, C. hanlinii, are its relatively small (45–90 μm diam when globose) and dark-coloured (olive yellow) spores, with a simple two-layered spore wall, of which the inner structural laminate layer 2 may be much thicker than that in other known Claroideoglomus species. The occasional pale staining of spore wall layer 1 in Melzer’s reagent is also distinctive in the species. Both species were grown in single-species pot cultures established from spores extracted from pot trap cultures with mixtures of rhizosphere soils and roots of plants colonizing maritime sand dunes near Natal, Brazil (A. ignota), and Varadero, Cuba (C. hanlinii). To date, these are the only sites in the world where these two fungi are known to occur, as confirmed by comparisons of their sequences with those deposited in available databases.