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Symbionts of Orchid Mycorrhiza

The Plants

All members of the family Orchidaceae are thought to form orchid mycorrhizas.

The Fungi

Most orchids associate with members of the form genus Rhizoctonia sensu lato. A few achlorophyllous orchid species have been recorded to associate with a variety of other genera, which may also form ectomycorrhizas or are known wood-rotting fungi or pathogens. The perfect stages of many Rhizoctonia have been determined and these are in the genera Ceratobasidium, Sebacina, Thanatephorus, Tulasnella, Waitea, and Ypsilonidium. The remaining fungi have been placed in the genera Armillarea, Marasmius, Hymenochaete, Xerotus, Fomes, Coriolus, Thelephora and Tomentella.



With more than 15,000 species, the orchid family is large and diverse. The fungi found in their roots include beneficial symbionts and some of no known function. Traditionally, the fungi were grouped into the anamorphic genus Rhizoctonia, because they were difficult to fruit. Use of modern techniques indicates that the symbionts include fungi from a variety of backgrounds.



Smith SE & Read DJ (2008) Mycorrhizal Symbiosis. Academic press, London.


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