Comparison of radial growth rate of mycorrhizal fungi isolated from 43 species of northern orchids

Authors: Lindén, Ben R.
Journal: Karstenia, Volume 28 (1988), Issue 1, pages 19-25.
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Abstract:  The investigation is part of a study devoted to the propagation of Scandinavian orchids. Endophytes from the roots of 43 orchid populations and, for comparison, from Moneses uniflora and four saprophytic fungi were isolated and the growth rates measured. The rates recorded ranged from 1.1 to 9.6 mm per 24 hours. The growth-retarding effect of tannin was also investigated. The response varied from total inhibition to no retarding effect. It is suggested that the differences in growth rates and response to retardants, which both seem to be dependent on the host taxonomy and ecology, can be of use in identifying the mycorrhizal endophytes.
Instead of the conventional isolating methods involving prolonged disinfection, the orchid roots were merely washed in soapy water, subjected to a high-pressure water jet, cut into segments and plated on plain water-agar medium. Contaminant-free cultures were easily achieved in this manner. Water-agar was also used for maintenance of cultures and growth rate observations.