| Inonotus obliquus | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Agaricomycetes |
| Order: | Hymenochaetales |
| Family: | Hymenochaetaceae |
| Genus: | Inonotus |
| Species: | I. obliquus |
| Binomial name | |
| Inonotus obliquus | |
| Synonyms[2] | |
Boletus obliquusAch. ex Pers. (1801) | |
Inonotus obliquus, commonly calledchaga (/ˈtʃɑːɡə/; aLatinization of the Russian wordча́га), is afungus in the familyHymenochaetaceae. It isparasitic onbirch and other trees. The sterileconk is irregularly formed and resembles burnt charcoal. It is not thefruiting body of the fungus, but asclerotium or mass ofmycelium, mostly black because of a substantial amount ofmelanin.[3][4] It is commonly marketed as adietary supplement for various health benefits but lacks sufficientscientific evidence for safety or effectiveness, and quality can vary due to inconsistent processing and labeling.[5]
Inonotus obliquus causes a whiteheart rot to develop in the host tree. The chaga spores enter the tree through wounds, particularly poorly healed branch stubs. The white rot decay will spread throughout theheartwood of the host. During the infection cycle, penetration of thesapwood occurs only around the sterile exteriormycelium mass.[6] The chaga fungus will continue to cause decay within the living tree for 10–80+ years. While the tree is alive, only sterile mycelial masses are produced (the black exterior conk). The sexual stage begins after the tree, or some portion of the tree, is killed by the infection.I. obliquus will begin to produce fertile fruiting bodies underneath the bark. These bodies begin as a whitish mass that turn to brown with time. Since the sexual stage occurs almost entirely under the bark, the fruiting body is rarely seen.[7] These fruiting bodies producebasidiospores which will spread the infection to other vulnerable trees.
The mycelialcanker is about 10–25 centimetres (4–10 in) wide, while the underlying crust can be 5–50 cm (2–19+1⁄2 in) long.[8]
The blacksclerotium has large concentrations ofmelanin.[9][10] Chaga contains extremely high concentrations ofoxalate, 2800–11200 mg total oxalates/100 g sclerotium, one of the highest reported in any organism.[11]
Similar species includeApiosporina morbosa,Diplodia tumefaciens, andEchinodontium tinctorium, as well as species ofFulvifomes andFomitiporia.[8]
Inonotus obliquus is found most commonly in theCircumboreal Region of the Northern Hemisphere, where it is distributed in birch forests.[6]
Generally found growing on birch (Betula spp.) trees, it has also been found on alder (Alnus spp.), beech (Fagus spp.) and poplar (Populus spp.).[12]
Attempts atcultivating this fungus onpotato dextrose agar and other simulatedmedia resulted in a reduced and markedly different production of metabolites.[13][14] Cultivated chaga developed a reduced number ofphytosterols, particularlylanosterol, an intermediate in the synthesis ofergosterol andlanostane-typetriterpenes.[13]
| Inonotus obliquus | |
|---|---|
| Mycological characteristics | |
 | Smoothhymenium |
 | No distinctcap |
 | Hymenium attachment is not applicable |
| Lacks astipe |
 | Ecology isparasitic |
 | Edibility ischoice |
It is commonly marketed as adietary supplement for various health benefits but lacks sufficientscientific evidence for safety or effectiveness, and quality can vary due to inconsistent processing and labeling.[5]
Chaga is traditionally grated into a fine powder and used to brew a beverage resemblingcoffee ortea which tastes strongly ofChinese herbal tea. However, caution is warranted with chronic use due to the extremely high concentrations ofoxalates in chaga.[15]
Hot water extraction is a common preparation. A decoction is created by simmering blocklike pieces of the chaga in numerous quarts of water until the water is reduced and the remaining liquid contains a portion of the chaga's concentrated water-soluble compounds. Such preparations, produced in China and Japan, are exported worldwide.[16] Theβ-D-glucans may have a content of approximately 35% in a pure extract.[17] If chaga tea is prepared at home, the chaga chunks can be reused multiple times.
Potawatomi people use the fungus, calledshkitagen in theirlanguage, as afirekeepingtinder. According to Potawatomi biologistRobin Wall Kimmerer, "Once an ember meetsshkitagen it will not go out but smolders slowly in the fungal matrix, holding its heat. Even the smallest spark, so fleeting and easily lost, will be held and nurtured if it lands on a cube ofshkitagen."[18]
The namechaga comes from theRussian name of the fungus,ча́га,čága, which in turn is borrowed from the word for "mushroom" inKomi,тшак,tšak, the language of theindigenous peoples in theKama River Basin, west of theUral Mountains. It is also known as theclinkerpolypore, cinder conk, black mass and birch canker polypore.[19] InEngland and officially inCanada, it is known as the sterile conk trunk rot ofbirch.[20]
Media related toInonotus obliquus at Wikimedia Commons
