There is a company in Czechia that produces a product called Symbivit that contains the spores of the Glomus fungus:
http://www.inoculumplus.eu/nos-produits-en/symbivit.
A specialist of this company in the answer to my question whether Glomus can protect the underground bodies of the terrestrial orchids answered me:
Arbuscular mycorrhizal fungi of the genus Glomus wait in the soil (or substrate) in the form of sleeping spores. In the moment when they will germinate and the won´t find the roots of a proper herbal partner, that orchids surely are not, they will die. Any effect to the plant (consequently to the suppression of a patogene) is fully vanishing.
What is then the protecting effect of Neudohum? Maybe that Neudohum contains the bark humus that contains different fungi and they protect the orchid roots (according Berthold´s theory).
Stanislav, Neudohum doesn't contain Glomus fungi. It must be the combination of fungi and micro organisms.
There are a lot of other fungi in the garden and the forest which show a protection effect at the orchid roots. Some fungi mycelium protects orchid roots against rotting but also strangles the plant.