Racocetra beninensis from sub-Saharan savannas : a new species in the Glomeromycetes with ornamented spores

A new fungal species is described under the epithet Racocetra beninensis (Racocetraceae, Glomeromycota). It forms white to creamy-white, globose to sub-globose (sometimes oval) glomerospores terminally on sporogenous Cells. Spores measure 195-335 mu m diam and have two spore walls: a three-layered outer wall and a three-layered inner wall. The Outer spore surface is ornamented with rounded wart-like projections that measure 0.9-2.8 x 0.9-3.8 mu m and are spaced (2.2-)4.0-11.0 mu m apart. The germination shield that forms on the outer surface of the inner wall is multiple-lobed (6-10 lobes) and (sub-)hyaline or occasionally yellowing with age. The lobes regularly bear a single germ tube initiation. The fungus differs from other Racocetra species by spore size and color, ornamentation type, and outer spore wall staining reaction. It has been frequently recovered from sites under natural vegetation and newly cultivated or post-harvest yam (Dioscorea spp.) fields in the sub-Saharan Sudan and Guinea savannas of Benin (West Africa).