In vitro-propagation of Nigritella (Orchidaceae-Orchideae) from seeds withthe help of mycorrhizal fungi

Two strains of the form genus Rhizoctonia, isolated from Nigritella rhellic ani roots stimulated germination and further development not only of Nigrit ella, but also that of Gymnadenia and Dactylorhiza. Seeds were sterilised b riefly in an adapted sterilization apparatus and put on media, which were i noculated with Rhizocronia before. Typical fungal coils (peloton) were visi ble only after swelling of the seeds, after the fungus had entered the prot ocorm through the rhizoids. Approximately one year after germination, the p rotocorms, which had developed shoots and roots, were established successfu lly in mineral soil. The investigation of roots of Nigritella from nature has shown that they we re infected more or less heavily throughout the year.