Molecular Systematics of Ganoderma: What Is Reishi?

Abstract

Volume 7, Issue 3, 2005 353 Ganoderma is a very distinctive genus of whiterot polypore fungi that is primarily characterized by the formation of a double-walled, generally echinulate basidiospore. Most Ganoderma species are very variable macromorphologically and lack micromorphological distinctiveness. As a consequence, earlier taxonomic studies in the genus have created many synonymous names and have resulted in largely ambiguous species delimitation and identifi cation systems, making species identifi cation in the genus virtually impossible. Ganoderma strains used in oriental folk medicine refer to Reishi and have traditionally been labeled Ganoderma lucidum (W.Curt.: Fr.) P. Karst. in the scientifi c literature. However, there is now accumulative evidence that most species reported as G. lucidum in most of the pharmacological and phytopathological studies were wrongly identifi ed. G. lucidum was fi rst described as Boletus lucidus by William Curtis in 1781 from a fi lbert plant (= Corylus avellana) in London, UK. Curtis’s original collection (i.e., the type specimen) has been lost. Th e actual type is represented in a color plate, which is in agreement with the International Code of Botanical Nomenclature. However, the typifi ed plate is of no use for providing cultural characteristics and genetic information that would be useful for distinguishing G. lucidum from the other British laccate Ganoderma. Over the years, at least 166 laccate Ganoderma species have been described worldwide, of which at least 48 names were, at some point, considered to be synonyms of others. Th ere is nevertheless a strong consensus about the true identity of G. lucidum among contemporary European mycologists. Molecular phylogenetic studies indicate that Ganoderma is a young genus in agreement with earlier morphological evidence as pointed out by the Norwegian mycologist Leif Ryvarden. DNA studies have shown that the G. lucidum species complex is composed of several species that can be diffi cult to distinguish from one another. Th ese species include the European G. valesiacum Boud.; G. ahamdii Stey., described from Pakistan; North American G. tsugae Murrill and G.oregonense Murrill; and other taxa variously labeled G. resinaceum Boud., G. oerstedii Fr., and G. praelongum Murrill. Recent genetic and biogeographic studies have indicated that most Ganoderma species are geographically restricted. G. lucidum is probably restricted to western parts of Europe, although its distribution range can possibly also include parts of Siberia and of north western regions of China. Based on molecular phylogenetic evidence, it appears that most collections labeled G. lucidum in North America do in fact best correspond to the taxon labeled G. resinaceum in Europe, whereas G. tsugae in North America is genetically very close to the “true” G. lucidum from Europe. Th is leads to the question of what is the Oriental Reishi? A nonexhaustive molecular survey of taxa labeled G. lucidum in Asia, including strains comMolecular Systematics of Ganoderma: What Is Reishi?