A TECHNIQUE FOR THE ESTABLISHMENT OF MYCORRHIZAL INFECTION IN ORCHID TISSUE GROWN IN ASEPTIC CULTURE

Abstract

SUMMARYTwo techniques for producing large quantities of mycorrhizal and non‐mycorrhizal orchid tissue for experimental purposes are described.Protocorm‐like masses of Dactylorhiza purpurella (T. & T. A. Steph.) Soó, were grown axenically in darkness on 2 % sucrose mineral salts medium with growth supplements at 22 °C. These cultures, derived from seed, were substantially larger than the original protocorms.Mycorrhizal infection of this tissue was achieved successfully in 100 ml conical flasks in which the protocorm‐like tissue was suspended on water agar only and the fungus inoculated on an adjoining cellulose, mineral salts slope.Infection, using several Rhizoctonia strains in this double‐culture system gave consistent mycorrhizas characteristic of natural protocorms and with extensive colonization of cortical tissue. Alternative inoculation methods using a single aqueous or agar medium and with recognized mycorrhizal strains, gave variable infection, frequently resulting in pathogenicity and host death. The advantage of the double culture system in providing large quantities of orchid mycorrhizal tissue for experimental studies is discussed.