Glomus compressum, a new arbuscular mycorrhizal fungus from different agro-ecosystems in Central Europe

A new arbuscular mycorrhizal (AM) fungus, Glomus compressum, was isolated from several agricultural systems all over Switzerland, southwestern Germany and northeastern France. It was also cultivated in trap cultures and in a monosporic pot culture using Hieracium pilosella as host plant. The new fungus differentiates golden-yellow to yellow brown, bi-layered spores, (50-)68-94(-103) pm in diameter, formed singly, in small clusters of 2-10 spores or in loose non-organized sporocarps with up to 34-50 spores. Glomus compressum can be distinguished from all other glomeromycotean fungal species by the combination of spore size and color, non-staining in Melzer's reagent, and its subtending hyphae that generally form a narrow, often irregular pore channel up to 5-40 pm long from the spore base. Phylogenetically, it forms a distinct clade within the Glomeraceae. The fungus is a good example for an AM fungus that could first be described unequivocally after a monosporic culture had successfully been established.