Glomus aureum, a new sporocarpic arbuscular mycorrhizal fungal species from European grasslands

Glomus aureum forms irregular sporocarps, 450-1200 x 510-1600 pm in size, without a peridium. Spores are randomly embedded between interwoven hyphae and amorphous material which stains purple in Melzer's reagent. Spores are subglobose to ovoid, seldom globose; (36-)55-65 x (30-)45-52 pm, or (27-)40-60 pm in diameter when round. Spores have two wall layers, in total 1.5-3(-4) μm thick. The innermost lamina of the laminated inner wall layer often closes the pore of the thick-walled hyphal attachment. Glomus aureum has some morphological similarities with G. pallidum from which it can be distinguished by its golden brown spore colour, differences in the wall structure, and the thickening of the inner wall layer of the subtending hypha for 10-30 μm from the spore base, forming a narrow pore channel in mature spores. Glomus aureum was isolated from grasslands in Germany, France, Switzerland and Italy.