Glomus badium, a new sporocarpic mycorrhizal fungal species from European grasslands with higher soil pH

Glomus badium forms small sporocarps with about 180-280 μm in diameter. The sporocarps have no peridum and contain 5-30 spores. The spores are situated around and partly within a whitish to yellowish gleba of interwoven intras porocarpic hyphae. Spores are reddish brown to dark brown to black, globose, subglobose to ovoid, 51- 90 x 75-120 μm in diameter. Spores have three wall layers, in total (5.5-)7-14 μm thick. The innermost layer usually closes the pore at the spore base together with a bridging septum formed by the middle layer. The subtending hypha of each spore is usually very short (<1- 2.5 μm) and, thus , the spore base is difficult to observe. The new species can easily be differentiated from other sporocarp-forming Glomus spp. by the structure and the size of the sporocarps and spores, the organisation of the spores in the sporocarps, the colour of the spore walls and in particular through the c1rnractetistics of the intrasporocarpic hyphae and the short subtending hypha at the spore base. A partial DNA sequence of the I SS ribosomal small subunit gene of spores of G. badium was determined. Phylogenetic analyses firmly placed the sequence into Glomus spp. of group A of the Glomeraceae, with no close matches among named sequences obtained from spores of other Glomus species. Several sequences from field collected roots infected with AMF showed a hi gh similarity to G. badium. Glomus badium is a frequent member of the arbuscular mycorrhizal fungi community of grasslands, grass-intercropped vineyards or olive fields, or no-till arable lands in Germany, F rance, Switzerland and Italy. It has been found in grasslands up to the tree line in the Alps, but so far, only in soils with pH 6-8.