Armillaria mellea, commonly known as honey fungus, is an edible basidiomycetefungus in the genusArmillaria. It is a plant pathogen and part of a cryptic species complex of closely related and morphologically similar species. It causes Armillaria root rot in many plant species and produces mushrooms around the base of trees it has infected. The symptoms of infection appear in the crowns of infected trees as discoloured foliage, reduced growth, dieback of the branches and death. The mushrooms are edible but some people may be intolerant to them. This species is capable of producing light via bioluminescence in its mycelium.
Armillaria mellea is widely distributed in temperate regions of the Northern Hemisphere. The fruit body or mushroom, commonly known as stump mushroom, stumpie, honey mushroom, pipinky or pinky, grows typically on hardwoods but may be found around and on other living and dead wood or in open areas.
Taxonomy
This section is missing information about links from subtaxa to current species pages (e.g. obscura → ostoyae); #Similar species ref may help. Please expand the section to include this information. Further details may exist on the talk page.(March 2021)
The species was originally named Agaricus melleus by Danish-Norwegian botanist Martin Vahl in 1790; it was transferred to the genus Armillaria in 1871 by Paul Kummer.[1] Numerous subtaxa have been described:
Armillaria mellea once included a range of species with similar features that have since been reclassified. The following are reassigned subtaxa, mostly variety-level entries from the 19th century:[6]
Illustration from James Sowerby's Coloured Figures of English Fungi or MushroomsHoney fungus rhizomorphs
The basidiocarp of each has a smooth cap 3 to 15cm (1 to 6in) in diameter,[15] convex at first but becoming flattened with age often with a central raised umbo, later becoming somewhat dish-shaped. The margins of the cap are often arched at maturity and the surface is sticky when wet. Though typically honey-coloured, this fungus is rather variable in appearance and sometimes has a few dark, hairy scales near the centre somewhat radially arranged. The gills are white at first, sometimes becoming pinkish-yellow or discoloured with age, broad and fairly distant, attached to the stipe at right angles or are slightly decurrent. The stipe is of variable length, up to about 20cm (8in) long and 3.5cm (1+1⁄2in) in diameter. It is fibrillose and of a firm spongy consistency at first but later becomes hollow. It is cylindrical and tapers to a point at its base where it is fused to the stipes of other mushrooms in the clump. It is whitish at the upper end and brownish-yellow below, often with a very dark-coloured base. There is a broad persistent skin-like ring attached to the upper part of the stipe. This has a velvety margin and yellowish fluff underneath and extends outwards as a white partial veil protecting the gills when young. The flesh of the cap is whitish and has a sweetish odour and flavour with a tinge of bitterness. Under the microscope, the spores are approximately elliptical, 7–9 by 6–7μm, inamyloid with prominent apiculi (short, pointed projections) at the base. The spore print is white. The basidia (spore-producing structures) lack basal clamps.[16][17]
The main part of the fungus is underground where a mat of mycelial threads may extend for great distances. They are bundled together in rhizomorphs that are black in this species.[17] The fungal body is not bioluminescent but its mycelia are luminous when in active growth.[18]
Hosts, signs, and symptoms
Armillaria mellea typically is symbiotic with hardwood trees and conifers,[19] this includes orchards, planted forests, vineyards,[20] and a few herbaceous plants.[21] There are few signs, and the ones that do exist are often hard to find. The most prominent sign is honey-coloured mushrooms at the base of the infected plant.[22] Additional signs include white, fan-shaped mycelia and black rhizomorphs with diameters between 1/32nd of an inch and 1/8th of an inch.[21] These usually are not as noticeable because they occur beneath the bark and in the soil, respectively.[21] The symptoms are much more numerous, including slower growth, dieback of branches, yellowing foliage,[22] rotted wood at base and/or roots, external cankers, cracking bark, bleeding stem, leaf wilting, defoliation, and rapid death.[21] Leaf wilting, defoliation, and dieback occur after the destruction of the cambium.[21]
Disease cycle
Armillaria mellea infects both through basidiospore[23] and penetration of host species by rhizomorphs[22] which can grow up to 1 meter (39in) long per year[24] to find new, living tissue to infect.[23] However, infection of living host tissue through basidiospores is quite rare.[21] Two basidiospores must germinate and fuse to be viable and produce mycelium.[21] In the late summer and autumn, Armillaria mellea produces mushrooms with notched gills, a ring near the cap base, and a white to golden color.[19] They do not always appear,[21] but when they do they can be found on both living and dead trees near the ground.[21] These mushrooms produce and release the sexually created basidiospore which is dispersed by the wind.[21] This is the only spore-bearing phase. The fungus overwinters as either rhizomorphs or vegetative mycelium.[25] Infected wood is weakened through decay in roots and tree base after destruction of the vascular cambium and underlying wood.[21]
Environment
Armillaria mellea prefers moist soil and lower soil temperatures[21] but it can also withstand extreme temperatures, such as forest fires, due to the protection of the soil.[19] It is found in many kinds of landscapes, including gardens, parks, vineyards, tree production areas, and natural landscapes.[21]
Distribution
Armillaria mellea is widespread in northern temperate zones. It has been found in North America, Europe and northern Asia, and It has been introduced to South Africa. The fungus grows parasitically on a large number of broadleaf trees. It fruits in dense clusters at the base of trunks or stumps.[26]
Ecology
Trees become infected by Armillaria mellea when rhizomorphs growing through the soil encounter uninfected roots. Alternatively, when infected roots come into contact with uninfected ones the fungal mycelium may grow across. The rhizomorphs invade the trunk, growing between the bark and the wood and causing wood decay, growth reduction and mortality. Trees that are already under stress are more likely to be attacked but healthy trees may also be parasitized. The foliage becomes sparse and discoloured, twig growth slows down and branches may die back. When they are attacked, the Douglas-fir, western larch and some other conifers often produce an extra large crop of cones shortly before dying. Coniferous trees also tend to ooze resin from infected areas whereas broad-leaved trees sometimes develop sunken cankers. A growth of fruiting bodies near the base of the trunk confirms the suspicion of Armillaria root rot.[27]
In 1893, the American mycologist Charles Horton Peck reported finding Armillaria fruiting bodies that were "aborted", in a similar way to specimens of Entoloma abortivum. It was not until 1974 that Roy Watling showed that the aborted specimens included cells of both Armillaria mellea and Entoloma abortivum. He thought that the Armillaria was parasitizing the Entoloma, a plausible hypothesis given its pathogenic behaviour.[28] However, a 2001 study by Czederpiltz, Volk and Burdsall showed that the Entoloma was in fact the microparasite. The whitish-grey malformed fruit bodies known as carpophoroids were the result of E.abortivumhyphae penetrating the Armillaria and disrupting its normal development.[29]
The main part of the fungus is underground where a mat of mycelial threads may extend for great distances. The rhizomorphs of A. mellea are initiated from mycelium into multicellular apices of rhizomorphs, which are multicellular vegetative organs that exclude soil from the interior of the rhizomorph tissues. The rhizomorphs spread through far greater distances through the ground than the mycelium. The rhizomorphs are black in this species.[17] The fungal body is not bioluminescent but its mycelia and rhizomorphs are luminous when in active growth.[18] A. mellea producing rhizomorphs is parasitic on woody plants of many species, including especially shrubs, hardwood and evergreen trees. In one example, A. mellea spread by rhizomorphs from an initially infected tree killed 600 trees in a prune orchard in 6 years. Each infected tree was immediately adjacent to an already infected one, the spread by rhizomorphs through the tree roots and soil. (Piper and Fletcher, 1903, Wash. Age. Exp. Sat. But., 59: 1–14); cited in Rhizomorph Development in A. mellea, Ph.D. thesis, by Philip Snider(1957), Farlow Herbarium Library Harvard Univ., 20 Divinity Ave., Cambridge, Mass.
Management
There are fungicides or management practices that will kill Armillariamellea after infection without damaging the infected plant, but these practicies are still being studied.[30] There are practices that can extend the life of the plant and prevent further spreading. The best way to extend the plant life is to improve the host condition through supplemental watering and fertilization.[22] To prevent further spread, regulate irrigation to avoid water stress, keep the root collar dry, control defoliating pathogens, remove stumps, fertilize adequately, avoid physical root damage and soil compaction, and don't plant trees that are especially susceptible to the disease in places where Armillaria mellea has been recorded.[21] There is also some evidence that biological control using the fungus genus Trichoderma may help. Trichoderma is a predator of Armillaria mellea and is often found in woodchips.[21] Therefore, chipping or grinding dead and infected roots will give Trichoderma its preferred habitat and help it proliferate. Solarization will also create an ideal habitat as dry soil and higher soil temperatures are preferable for Trichoderma but poor conditions for Armillaria mellea.[21]
Edibility
Parboiling honey fungus
Armillaria mellea mushroom are considered good edibles, though not preferred by some, and the tough stalks are usually excluded.[15] Some individuals have reported "allergic" reactions that result in stomach upsets. Some authors suggest not collecting mushrooms from the wood of various trees, including hemlock, buckeye, eucalyptus, and locust.[citation needed] They may have been used medicinally by indigenous peoples as a laxative.[31]
The mushrooms have a taste that has been described as slightly sweet and nutty, with a texture ranging from chewy to crunchy, depending on the method of preparation. Parboiling mushrooms before consuming removes the bitter taste present in some specimens, and may reduce the amount of gastrointestinal irritants.[32] According to one guide, they must be cooked before eating.[33] Drying the mushrooms preserves and intensifies their flavour, although reconstituted mushrooms tend to be tough to eat.[34] The mushrooms can also be pickled and roasted.
Chemistry
Several bioactive compounds have been isolated and identified from the fruit bodies. The triterpenes 3β-hydroxyglutin-5-ene, friedelane-2α,3β-diol, and friedelin were reported in 2011.[35]Indole compounds include tryptamine, L-tryptophan and serotonin.[36]
The fungus produces cytotoxic compounds known as melleolides. Melleolides are made from orsellinic acid and protoilludane sesquiterpene alcohols via esterification. A polyketide synthase gene, termed ArmB, was identified in the genome of the fungus, which was found expressed during melleolide production. The gene shares c. 42% similarity with the orsellinic acid synthase gene (OrsA) in Aspergillus nidulans. Characterization of the gene proved it to catalyze orsillinic acid in vitro. It is a non-reducing iterative type 1 polyketide synthase. Co-incubation of free orsellinic acid with alcohols and ArmB showed cross-coupling activity. Therefore, the enzyme has transesterification activity. Also, there are other auxiliary factors suspected to control substrate specificity.[37] Additionally, halogen modifications have been observed. Overexpression of annotated halogenases (termed ArmH1-5) and characterization of the subsequent enzymes revealed in all five enzymes the chlorination of mellolide F. In vitro reactions of free standing substrates showed that the enzymes do not require auxiliary carrier proteins for substrate delivery.[38]
Importance
Armillaria mellea has been reported in almost every state with the continental United States.[39] It is one of the most common causes of death in trees and shrubs in both natural and human cultivated habitats, and cause steady and substantial losses.[39]
Pathogenesis
Armillaria mellea infects new hosts through rhizomorphs[22][23] and basidiospores.[40] It is rare for basidiospores to be successful in infecting new hosts and often colonize woody debris instead,[21] but rhizomorphs, however, can grow up to ten feet long in order to find a new host.[23]
Armillaria is a genus of fungi that includes the A. mellea species known as honey fungi that live on trees and woody shrubs. It includes about 10 species formerly categorized summarily as A. mellea. Armillarias are long-lived and form the largest living fungi in the world. The largest known organism covers more than 3.4 square miles (8.8 km2) in Oregon's Malheur National Forest and is estimated to be 2,500 years old. Some species of Armillaria display bioluminescence, resulting in foxfire.
Trichoderma viride is a fungus and a biofungicide.
Entoloma is a genus of fungi in the order Agaricales. Called pinkgills in English, basidiocarps are typically agaricoid, though a minority are gasteroid. All have salmon-pink basidiospores which colour the gills at maturity and are angular (polyhedral) under a microscope. The genus is large, with almost 2000 species worldwide. Most species are saprotrophic, but some are ectomycorrhizal, and a few are parasitic on other fungi. The type, Entoloma sinuatum, is one of several Entoloma species that are poisonous, typically causing mild to severe gastrointestinal illness.
Mycelial cords are linear aggregations of parallel-oriented hyphae. The mature cords are composed of wide, empty vessel hyphae surrounded by narrower sheathing hyphae. Cords may look similar to plant roots, and also frequently have similar functions; hence they are also called rhizomorphs. As well as growing underground or on the surface of trees and other plants, some fungi make mycelial cords which hang in the air from vegetation.
Armillaria luteobubalina, commonly known as the Australian honey fungus, is a species of mushroom in the family Physalacriaceae. Widely distributed in southern Australia, the fungus is responsible for a disease known as Armillaria root rot, a primary cause of Eucalyptus tree death and forest dieback. It is the most pathogenic and widespread of the six Armillaria species found in Australia. The fungus has also been collected in Argentina and Chile. Fruit bodies have cream- to tan-coloured caps that grow up to 10 cm (4 in) in diameter and stems that measure up to 20 cm (8 in) long by 1.5 cm (1 in) thick. The fruit bodies, which appear at the base of infected trees and other woody plants in autumn (March–April), are edible, but require cooking to remove the bitter taste. The fungus is dispersed through spores produced on gills on the underside of the caps, and also by growing vegetatively through the root systems of host trees. The ability of the fungus to spread vegetatively is facilitated by an aerating system that allows it to efficiently diffuse oxygen through rhizomorphs—rootlike structures made of dense masses of hyphae.
Armillaria tabescens is a species of fungus in the family Physalacriaceae. It is a plant pathogen. The mycelium of the fungus is bioluminescent.
Heterobasidion annosum is a basidiomycete fungus in the family Bondarzewiaceae. It is considered to be the most economically important forest pathogen in the Northern Hemisphere. Heterobasidion annosum is widespread in forests in the United States and is responsible for the loss of one billion U.S. dollars annually. This fungus has been known by many different names. First described by Fries in 1821, it was known by the name Polyporus annosum. Later, it was found to be linked to conifer disease by Robert Hartig in 1874, and was renamed Fomes annosus by H. Karsten. Its current name of Heterobasidion annosum was given by Brefeld in 1888. Heterobasidion annosum causes one of the most destructive diseases of conifers. The disease caused by the fungus is named annosus root rot.
Rigidoporus microporus is a plant pathogen, known to cause white root rot disease on various tropical crops, such as cacao, cassava, tea, with economical importance on the para rubber tree.
Pyrrhoderma noxium is a species of plant pathogen. It attacks a wide range of tropical plants, and is the cause of brown root rot disease. It has been described as "an aggressive and destructive pathogen". The pathogen invades roots with contact between roots of a potential host with the substrate on which the fungus is growing.
Armillaria fuscipes is a plant pathogen that causes Armillaria root rot on Pinus, coffee plants, tea and various hardwood trees. It is common in South Africa. The mycelium of the fungus is bioluminescent.
Armillaria novae-zelandiae is a species of mushroom-forming fungus in the family Physalacriaceae. This plant pathogen species is one of four Armillaria species that have been identified in Aotearoa New Zealand the others are A. limonea,A. hinnulea, A. aotearoa).
Armillaria gallica is a species of honey mushroom in the family Physalacriaceae of the order Agaricales. The species is a common and ecologically important wood-decay fungus that can live as a saprobe, or as an opportunistic parasite in weakened tree hosts to cause root or butt rot. It is found in temperate regions of Asia, North America, and Europe. The species forms fruit bodies singly or in groups in soil or rotting wood. The fungus has been inadvertently introduced to South Africa. Armillaria gallica has had a confusing taxonomy, due in part to historical difficulties encountered in distinguishing between similar Armillaria species. The fungus received international attention in the early 1990s when an individual colony living in a Michigan forest was reported to cover an area of 15 hectares, weigh at least 9.5 tonnes, and be 1,500 years old. This individual is popularly known as the "humongous fungus", and is a tourist attraction and inspiration for an annual mushroom-themed festival in Crystal Falls. Recent studies have revised the fungus's age to 2,500 years and its size to about 400 tonnes, four times the original estimate.
Armillaria nabsnona is a species of fungus in the family Physalacriaceae. The species is found in the west coast of North America, Hawaii, and Japan, where it grows on decaying hardwoods, particularly species of alder. Its fruit bodies have convex to flattened orange-brown caps up to 7 cm in diameter, brown stipes, and whitish to pinkish-tan gills.
Mycoforestry is an ecological forest management system implemented to enhance forest ecosystems and plant communities, by introducing the mycorrhizal and saprotrophic fungi. Mycoforestry is considered a type of permaculture and can be implemented as a beneficial component of an agroforestry system. It can enhance the yields of tree crops and produce edible mushrooms, an economically valuable product. By integrating plant-fungal associations into a forestry management system, native forests can be preserved, wood waste can be recycled back into the ecosystem, carbon sequestration can be increased, planted restoration sites are enhanced, and the sustainability of forest ecosystems are improved. Mycoforestry is an alternative to the practice of clearcutting, which removes dead wood from forests, thereby diminishing nutrient availability and reducing soil depth.
Entoloma abortivum, commonly known as the aborted entoloma or shrimp of the woods, is an edible mushroom in the Entolomataceae family of fungi. In Mexico they are called “Totlcoxcatl”, meaning “turkey wattle”, due to its irregular shape. Caution should be used in identifying the species before eating. First named Clitopilus abortivus by Miles Joseph Berkeley and Moses Ashley Curtis, it was given its current name by the Dutch mycologist Marinus Anton Donk in 1949.
Armillaria root rot is a fungal root rot caused by several different members of the genus Armillaria. The symptoms are variable depending on the host infected, ranging from stunted leaves to chlorotic needles and dieback of twigs and branches. However, all infected hosts display symptoms characteristic of being infected by a white rotting fungus. The most effective ways of management focus on limiting the spread of the fungus, planting resistant species, and removing infected material. This disease poses a threat to the lumber industry as well as affecting recreational areas.
Armillaria ostoyae is a species of fungus (mushroom), pathogenic to trees, in the family Physalacriaceae. In the western United States, it is the most common variant of the group of species under the name Armillaria mellea. A. ostoyae is common on both hardwood and conifer wood in forests west of the Cascade Range in Oregon, United States. It has decurrent gills and the stipe has a ring. The mycelium invades the sapwood and is able to disseminate over great distances under the bark or between trees in the form of black rhizomorphs ("shoestrings"). In most areas of North America, Armillaria ostoyae can be separated from other species by its physical features: cream-brown colors, prominent cap scales, and a well-developed stem ring distinguish it from other Armillaria. Like several other Armillaria, the mycelium of Armillaria ostoyae can display bioluminescence, resulting in foxfire.
Roy Watling is a Scottish mycologist who has made significant contributions to the study of fungi both in the identification of new species and correct taxonomic placement, as well as in fungal ecology.
Agroathelia rolfsii is a corticioid fungus in the order Amylocorticiales. It is a facultative plant pathogen and is the causal agent of "southern blight" disease in crops.
↑ Peck CH. (1891). "Report of the Botanist (1890)". Annual Report on the New York State Museum of Natural History. 44: 117–87 (see p. 150).
1 2 3 4 5 Barla JB. (1887). "Liste des champignons nouvellement observés dans le département des Alpes-Maritimes". Bulletin de la Société Mycologique de France (in French). 3 (2): 138–44.
↑ Cha JY, Igarashi T (1995). "A note on Armillaria mellea subsp. nipponica subsp. nov. in Japan". Mycoscience. 36 (2): 143–6. doi:10.1007/BF02268548. S2CID84793024.
↑ Calonge FD, Menezes de Sequeira M (2003). "Contribución al catálogo de los hongos de Madeira (Portugal)". Boletín de la Sociedad Micológica de Madrid (in Spanish). 27: 277–308.
↑ Ross-Davis AL, Hanna JW, Kim MS, Klopfenstein NB (2012). "Advances toward DNA-based identification and phylogeny of North American Armillariaspecies using elongation factor-1 alpha gene". Mycoscience. 53 (2): 161–5. doi:10.1007/s10267-011-0148-x. S2CID83996766.
↑ Hennings P. (1895). "Fungi camerunenses I". Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie (in German). 22: 72–111 (see p. 107).
↑ Peck CH. (1893). "Report of the Botanist (1892)". Annual Report on the New York State Museum of Natural History. 46: 85–149 (see p. 134).
↑ Peck CH. (1896). "Report of the Botanist (1894)". Annual Report on the New York State Museum of Natural History. 48: 103–337 (see p. 265).
1 2 Gillet CC. (1874). Les Hyménomycètes ou Description de tous les Champignons qui Croissent en France (in French). Vol.1. Alençon: Ch. Thomas. p.84.
↑ Hennings P. (1900). "Fungi monsunenses". Monsunia. 1: 1–38.
↑ Karsten PA. (1879). "Rysslands, Finlands och den Skandinaviska halföns Hattsvampar. Förra Delen: Skifsvampar". Bidrag till Kännedom av Finlands Natur och Folk (in German). 32: 22.
↑ Not supported by mycobank, which reports a Agaricus sulphureus Weinm. taxon.
↑ Roberts P, Evans S (2011). The Book of Fungi. Chicago, Illinois: University of Chicago Press. p.63. ISBN978-0-226-72117-0.
↑ Williams, RE; Shaw, CG; Wargo, PM; Sites, WH (1989-04-01). "Armillaria Root Disease". Forest Insect & Disease Leaflet 78. US Department of Agriculture Forest Service. Retrieved 2013-10-17.
↑ Kuo, Michael (2004-10-01). "Entoloma abortivum". MushroomExpert.Com. Retrieved 2013-10-19.
↑ Czederpiltz DL, Volk TJ, Burdsall HH Jr (2001). "Field observations and inoculation experiments to determine the nature of the carpophoroids associated with Entoloma abortivum and Armillaria". Mycologia. 93 (5): 841–51. doi:10.2307/3761750. JSTOR3761750.
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