Lingzhi (mushroom)

Lingzhi (Ganoderma sichuanense), also known as reishi, is a polypore fungus ("bracket fungus") native to East Asia belonging to the genus Ganoderma. Its reddish brown, varnished, kidney-shaped cap with bands and peripherally inserted stem give it a distinct fan-like appearance. When fresh, the lingzhi is soft, cork-like, and flat. It lacks gills on its underside, and instead releases its spores via fine pores (80–120 μm) in yellow colors. In nature, it grows at the base and stumps of deciduous trees, especially maples. Lingzhi may be cultivated on hardwood logs, sawdust, or woodchips. The lingzhi mushroom is used in traditional Chinese medicine.

Taxonomy Lingzhi, also known as reishi from its Japanese pronunciation, is the ancient "mushroom of immortality", revered for over 2,000 years (with some evidence suggesting use in Neolithic China 6,800 years ago). However, as of 2023 there is an ongoing debate on which one of the described Ganoderma species is the true lingzhi mushroom. It is also likely that a few similar Ganoderma species were considered interchangeable. In the scientific literature, the lingzhi mushroom is ambiguously referred to as:

Ganoderma sichuanense — the currently accepted name, described by Zhao and Zhang (1983). Ganoderma lingzhi — described by Cao et al. (2012) as a novel species that may be the best fit for traditional definitions of the lingzhi mushroom. However, Du et al. (2023) found that it is the same species as G. sichuanense, so it is now treated as a later synonym. Ganoderma lucidum — the type species of Ganoderma was first described in 1781 by Curtis as Boletus lucidus based on European collections. In 1881 Karst designated it as the type species of his new genus Ganoderma, as Ganoderma lucidum. Early literature used G. lucidum for collections from China, but it was later established that Asian populations are distinct from European, both morphologically and phylogenetically. As the lingzhi fungus is strongly rooted in culture, the old name persists, even though it is well established that G. sichuanense and G. lucidum are distinct species. One source employed to solve the task of identifying the traditional lingzhi mushroom is the 16th century Chinese herbal compendium, the Bencao Gangmu (1578). There, a number of different lingzhi-like mushrooms defined by color were used for different purposes. No exact current species can be attached to these ancient lingzhi for certain, but according to Dai et al. (2017), as well as other researchers, and based on molecular work, red lingzhi is most likely to be Ganoderma sichuanense. Ganoderma sichuanense is the most widely found species in Chinese herb shops today, and the fruiting bodies are widely cultivated in China and shipped to many other countries. About 7–10 other Ganoderma species are also sold in some shops, but have different Chinese and Latin names, and are considered different in their activity and functions. The differences are based on concentrations of triterpenes such as ganoderic acid and its derivatives, which vary widely among species. Research on the genus is ongoing, but a number of recent phylogenetic analyses have been published in recent years.

Nomenclature Petter Adolf Karsten first described the genus Ganoderma in 1881. He designated as its type species a European fungus named Boletus lucidus by English botanist William Curtis in 1781. Since then, many other Ganoderma species have been described. The lingzhi's botanical names have Greek and Latin roots. Ganoderma derives from the Greek ganos (γανος; 'brightness'), and derma (δερμα; 'skin; together; shining skin'). The specific epithet, sichuanense, comes from the Sichuan Chinese province. The common name, lingzhi, comes from Chinese, meaning 'divine mushroom'.

Varieties It was once thought that G. lingzhi generally occurred in two growth forms: a large, sessile, specimen with a small or nonexistent stalk, found in North America, and a smaller specimen with a long, narrow stalk, found mainly in the tropics. However, recent molecular evidence has identified the former, stalkless, form as a distinct species called G. sessile, a name given to North American specimens by William Alfonso Murrill in 1902. Environmental conditions play a substantial role in the lingzhi's manifest morphological characteristics. For example, elevated carbon dioxide levels result in stem elongation in lingzhi. Other formations include antlers without a cap, which may also be related to carbon dioxide levels. The three main factors that influence fruit body development morphology are light, temperature, and humidity. While water and air quality play a role in fruit body development morphology, they do so to a lesser degree.

Distribution and habitat Ganoderma lingzhi is found in East Asia growing as a parasite or saprotroph on a variety of trees. Ganoderma curtisii and Ganoderma ravenelii are the closest relatives of the lingzhi mushroom in North America. In the wild, lingzhi grows at the base and stumps of deciduous trees, especially maples. Today, lingzhi is effectively cultivated on sawdust, woodchips, and hardwood logs.

Uses

Chemistry

Ganoderma lucidum contains diverse chemicals, including triterpenes (ganoderic acids), which have a molecular structure similar to that of steroid hormones. It also contains phytochemicals found in fungal materials, including polysaccharides (such as beta-glucan), coumarin, mannitol, and alkaloids. Sterols isolated from the mushroom include ganoderol, ganoderenic acid, ganoderiol, ganodermanontriol, lucidadiol, and ganodermadiol.

Folk medicine Because of its bitter taste, lingzhi is traditionally prepared as a hot water extract product for use in folk medicine. Thinly sliced or pulverized lingzhi (either fresh or dried) is added to boiling water which is then reduced to a simmer, covered, and left for 2 hours. The resulting liquid is dark and fairly bitter in taste. The red lingzhi is often more bitter than the black. The process is sometimes repeated to increase the concentration. Alternatively, it can be used as an ingredient in a formula decoction, or used to make an extract (in liquid, capsule, or powder form).

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