Conservation Potentials of Mycorrhizal Fungi Root Cultures of 23 North American Orchids from Herbarium Specimens

Jay A Yoder, Mallory P Dame

Abstract

Root samples from 23 species of preserved orchid specimens dating back to 1884, and housed in the Jacobs Herbarium at Wittenberg University (Ohio, USA), were sampled for culturable mycorrhizal fungi to determine if herbarium specimens could be enlisted as a source of fungi for conservation purposes (e.g., symbiotic seed germination). Root segments were detached from the specimens, soaked one hour in water, macerated, and immersed in three different types of standard culture media. To verify that this sampling technique was effective, a positive control was established that involved living roots of a greenhouse specimen. After >one week incubation at ambient temperature, seven of 33 orchid herbarium specimens yielded fungal colonies. None of the 800+ Petri plates prepared in this manner yielded living fungus cultures assignable to typical orchid mycorrhizal genera. We conclude that herbarium specimens are generally void of living Rhizoctonia-like fungi, thereby placing a heavier burden on fresh material as a source of these fungi for orchid conservation.