Armillaria gallica
Encyclopedia
Armillaria gallica is a species of honey mushroom in the Physalacriaceae
family of the Agaricales
order. 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 has a widespread distribution, being found in temperate regions of Asia, North America, and Europe, and 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 (37.1 acre), weigh at least 9500 kilograms (20,943.9 lb), and be 1,500 years old. This individual is popularly known as the "humungous fungus", and is a tourist attraction and inspiration for an annual mushroom-themed festival in Crystal Falls
.
Armillaria gallica is a largely subterranean fungus, and it produces fruit bodies that are up to about 10 cm (3.9 in) in diameter, yellow-brown, and covered with small scales. On the underside of the caps
are gills that are white to creamy or pale orange. The stem
may be up to 10 cm (3.9 in) long, with a white cobwebby ring
that divides the color of the stem into pale orange to brown above, and lighter-colored below. The fungus can develop an extensive system of underground root-like structures, called rhizomorphs, that help it to efficiently decompose dead wood in temperate broadleaf and mixed forests
. It has been the subject of considerable scientific research due to its importance as a plant pathogen, its ability to bioluminesce
, its unusual life cycle
, and its ability to form large and long-lived colonies
.
and taxonomy
of the species now known as Armillaria gallica, paralleling that surrounding the genus Armillaria. The type species
, Armillaria mellea
, was until the 1970s believed to be a pleiomorphic species with a wide distribution, variable pathogenicity, and one of the broadest host
ranges known for the fungi. In 1973, Veikko Hintikka reported a technique to distinguish between Armillaria species by growing them together as single spore
isolates on petri dish
es and observing changes in the morphology
of the cultures. Using a similar technique, Kari Korhonen
showed in 1978 that the European Armillaria mellea species complex
could be separated into five reproductively isolated species, which he named "European Biological Species" (EBS) A through E. About the same time, the North American A. mellea was shown to be ten different species (North American Biological Species, or NABS I through X); NABS VII was demonstrated shortly after to be the same species as EBS E. Because several research groups had worked with this widely distributed species, it was assigned several different names.
The species that Korhonen called EBS B was named A. bulbosa by Helga Marxmüller in 1982, as it was thought to be equivalent to Armillaria mellea var. bulbosa, first described by Joseph Barla in 1887, and later raised to species status by Josef Velenovský in 1927. In 1973, the French mycologist Henri Romagnesi
, unaware of Velenovský's publication, published a description of the species he called Armillariella bulbosa, based on specimens he had found near Compiègne
and Saint-Sauveur-le-Vicomte
in France. These specimens were later demonstrated to be the same species as the EBS E of Korhonen; EBS B was later determined to be A. cepistipes
. Therefore, the name A. bulbosa was a misapplied name for EBS E. In 1987 Romagnesi and Marxmüller renamed EBS E to Armillaria gallica. Another synonym
, A. lutea, had originally been described by Claude Casimir Gillet
in 1874, and proposed as a name for EBS E. Although the name had priority
due to its early publication date, it was rejected as a nomen ambiguum because of a lack of supporting evidence to identify the fungus, including a specimen, type locality, and incomplete collection notes. A. inflata (Velenovský, 1920) may represent another synonym, but the type specimens were not preserved, so it is considered a dubious name (nomen dubium
). As of 2010, both the Index Fungorum
and MycoBank
consider Armillaria gallica Marxm. & Romagn. to be the current name, with A. bulbosa and A. lutea as synonyms.
Phylogenetic analysis of North American Armillaria species based on analysis of amplified fragment length polymorphism
data suggests that A. gallica is most closely related to A. sinapina, A. cepistipes, and A. calvescens. These results are similar to those reported in 1992 that compared sequences of nuclear ribosomal DNA
.
The specific epithet gallica is botanical Latin
for "French" (from Gallia, "Gaul"), and refers to the type locality. The prior name bulbosa is Latin for "bulb-bearing, bulbous" (from bulbus and the suffix -osa). Armillaria is derived from the Latin armilla, or "bracelet".
of Armillaria gallica have caps
that are 2.5 – broad, and depending on their age, may range in shape from conical to convex to flattened. The caps are brownish-yellow to brown when moist, often with a darker-colored center; the color tends to fade upon drying. The cap surface is covered with slender fibers (same color as the cap) that are erect, or sloping upwards.
When the fruit bodies are young, the underside of the caps have a cottony layer of tissue stretching from the edge of the cap to the stem—a partial veil
—which serves to protect the developing gills. As the cap grows in size the membrane is eventually pulled away from the cap to expose the gills. The gills have an adnate (squarely attached) to somewhat decurrent (extending down the length of the stem) attachment to the stem. They are initially white, but age to a creamy or pale orange covered with rust-colored spots. The stem
is 4 – long and 0.6 – thick, and almost club-shaped with the base up to 1.3 – thick. Above the level of the ring
, the stem is pale orange to brown, while below it is whitish or pale pink, becoming grayish-brown at the base. The ring is positioned about 0.4 – below the level of the cap, and may be covered with yellowish to pale-brownish woolly cottony mycelia
. The base of the stem is attached to rhizomorphs, black root-like structures 1–3 mm in diameter. While the primary function of the below-ground mycelia is to absorb nutrients from the soil, the rhizomorphs serve a more exploratory function, to locate new food bases.
, they appear whitish. They have an ellipsoid or oblong shape, usually contain an oil droplet, and have dimensions of 7–8.5 by 5–6 µm
. The spore-bearing cells, the basidia
, are club-shaped, four-spored (rarely two-spored), and measure 32–43 by 7–8.7 µm. Other cells present in the fertile hymenium
include the cheilocystidia (cystidia
present on the edge of a gill), which are club-shaped, roughly cylindrical and 15–25 by 5.0–12 µm. Cystidia are also present on the stem (called caulocystidia), and are broadly club-shaped, measuring 20–55 by 11–23 µm. The cap cuticle
is made of hypha
e that are irregularly interwoven and project upward to form the scales seen on the surface. The hyphae that make up the surface scales typically measure 26–88 µm long by 11–27 µm thick and can be covered with a crust of pigment
. Clamp connection
s are present in the hyphae of most tissues.
cheese.
is rather similar in appearance, and can only be reliably distinguished from A. gallica by observing microscopic characteristics. A. calvescens has a more northern distribution, and in North America, is rarely found south of the Great Lakes
. A. mellea
has a thinner stem than A. gallica, but can be more definitively distinguished by the absence of clamps at the base of the basidia. Similarly, A. cepistipes and A. gallica are virtually identical in appearance (especially older fruit bodies), and are identified by differences in geographical distribution, host range, and microscopic characteristics. Molecular
methods have been developed to discriminate between the two species by comparing DNA sequence
s in the gene
coding translation elongation factor 1-alpha.
-containing metabolite
s such as arnamiol, a natural product
that is classified as a sesquiterpenoid
aryl
ester
. Although the specific function of arnamiol is not definitively known, similar chemicals present in other Armillaria species are thought to play a role in inhibiting the growth of antagonistic bacteria or fungi, or in killing cells of the host plant prior to infection.
) of Armillaria gallica are known to be bioluminescent. Experiments have shown that the intensity of the luminescence is enhanced when the mycelia are disturbed during growth or when they are exposed to fluorescent light. Bioluminescence is caused by the action of luciferase
s, enzymes that produce light by the oxidation of a luciferin
(a pigment
). The biological purpose of bioluminescence in fungi is not definitively known, although several hypotheses have been suggested: it may help attract insects to help with spore dispersal, it may be a by-product of other biochemical functions, or it may help deter heterotroph
s that might consume the fungus.
in the early 1990s, during an unrelated research project to study the possible biological effects of extremely low frequency
radio stations, which were being investigated as a means to communicate with submerged submarines. In one particular forest stand, Armillaria-infected oak
trees had been harvested, and their stumps were left to rot in the field. Later, when red pines were planted in the same location, the seedlings were killed by the fungus, identified as A. gallica (then known as A. bulbosa). Using molecular genetics
, they determined that the underground mycelia
of one individual fungal colony
covered 15 ha (37.1 acre), weighing over 9500 kilograms (20,943.9 lb), with an estimated age of 1,500 years. The analysis used restriction fragment length polymorphism
(RFLP) and random amplification of polymorphic DNA
(RAPD) to examine isolates
collected from fruit bodies and rhizomorphs (underground aggregations of fungal cells that resemble plant roots) along 1 kilometre (0.621372736649807 mi) transect
s in the forest. The 15-hectare area yielded isolates that had identical mating type
alleles and mitochondrial DNA
restriction fragment
patterns; this degree of genetic similarity indicated that the samples were all derived from a single genetic individual, or clone
, that had reached its size through vegetative growth
. In their conclusion the authors noted: "This is the first report estimating the minimum size, mass, and age of an unambiguously defined fungal individual. Although the number of observations for plants and animals is much greater, members of the fungal kingdom should now be recognized as among the oldest and largest organisms on earth." After the Nature
paper was published, major media outlets from around the world visited the site where the specimens were found; as a result of this publicity, the individual acquired the common name
"humongous fungus". There was afterward some scholarly debate as to whether the fungus qualified to be considered in the same category as other large organisms such as the blue whale
or the giant redwood.
The fungus has since become a popular tourist attraction in Michigan, and has inspired a "Humongous Fungus Fest" held annually in August in Crystal Falls
. The organism was the subject of a Late Show Top Ten List on Late Night with David Letterman
, and an advertising campaign by the rental company U-Haul
.
of A. gallica includes two diploidization–haploidization events. The first of these is the usual process of cell fusion
(forming a diploid) followed by meiosis
during the formation of haploid basidiospore
s. The second event is more cryptic, and occurs before fruit body formation. In most basidiomycetous fungi, the hyphae of compatible mating type
s will fuse to form a two-nucleate
, or dikaryotic stage; this stage is not observed in Armillaria species, which have cells that are mostly monokaryotic and diploid. Genetic analyses suggest that the dikaryotic mycelia undergo an extra haploidization event prior to fruit body formation to create a genetic mosaic. These regular and repeating haploidization events result in increased genetic diversity
, which helps the fungus to adapt to unfavorable changes in environmental conditions, like drought.
The growth rate of A. gallica rhizomorphs is between 0.3 and 0.6 m (0.984251968503937 and 2 ft) per year. Population genetic
studies of the fungus conducted in the 1990s demonstrated that genetic individuals grow mitotically
from a single point of origin to eventually occupy territories that may include many adjacent root systems over large areas (several hectare
s) of forest floor. Based on the low mutation rate
s observed in large, long-lived individuals, A. gallica appears to have an especially stable genome
. It has also been hypothesized that genetic stability may result from self-renewing mycelial repositories of nuclei with stem cell
-like properties.
Province of South Africa, where it is thought to have been introduced
from potted plants imported from Europe during the early colonization of Cape Town. In Scandinavia, it is absent in areas with very cold climates, like Finland or Norway, but it is found in southern Sweden. It is thought to be the most prevalent low altitude species of Armillaria in Great Britain and France. The upper limits of its altitude vary by region. In the French Massif Central
, it is found up to 1100 m (3,608.9 ft), while in Bavaria, which has a more continental climate
, the upper limit of distribution reaches 600 m (1,968.5 ft). In Serbia
n forests, it is the most common Armillaria between elevations of 70 to 1450 m (229.7 to 4,757.2 ft). Field studies suggest that A. gallica prefers sites that are low in organic matter
and have high soil pH
s.
In North America, it is common east of the Rocky Mountains
, but rare in the Pacific Northwest
. In California, where it is widely distributed, the fungus is found in a variety of plant communities, including aspen, coastal oak woodland, Douglas Fir, Klamath mixed conifer
, montane hardwood, montane hardwood-conifer, montane riparian
, Redwood, Sierran mixed conifer, valley oak
woodland, valley-foothill riparian, and White Fir
. It was found to be the most common Armillaria species in hardwood and mixed oak forests in western Massachusetts
.
A Chinese study published in 2001 used the molecular biological
technique restriction fragment length polymorphism
to analyze the differences in DNA sequence
between 23 A. gallica specimens collected from the Northern Hemisphere. The results suggest that based on the restriction fragment length polymorphism patterns observed, there are four global A. gallica subpopulations: the Chinese, European, North American–Chinese, and North American–European geographical lineages
. A 2007 study on the northeastern and southwestern Chinese distribution of Armillaria, using fruit body and pure culture morphology, concluded that there are several unnamed species (Chinese biological species C, F, H, J and L) that are similar to the common A. gallica.
Armillaria gallica is a weaker pathogen than the related A. mella or A. solidipes, and is considered a secondary parasite—typically initiating infection only after the host's defenses have been weakened by insect defoliation, drought, or infection by another fungus. Fungal infection can lead to root rot
or butt rot
. As the diseased trees die, the wood dries, increasing the chance of catching fire after being struck by lightning. The resulting forest fire may in turn kill the species that killed the trees. Plants that are under water stress
caused by dry soils or waterlogging
are more susceptible to infection by A. gallica. It has been shown to be one of several Armillaria species responsible for widespread mortality of oak
trees in the Arkansas Ozarks. The fungus has also been shown to infect Daylily
in South Carolina
, Northern highbush blueberry
(Vaccinium corymbosum) in Italy and vineyards (Vitis
species) of Rías Baixas
in northwestern Spain. The latter infestation "may be related to the fact that the vineyards from which they were isolated were located on cleared forestry sites". When A. solidipes and A. gallica co-occur in the same forest, infection of root systems by A. gallica may reduce damage or prevent infection from A. solidipes.
Armillaria gallica can develop an extensive subterranean system of rhizomorphs, which helps it to compete with other fungi for resources or to attack trees weakened by other fungi. A field study in an ancient broadleaved woodland in England showed that of five Armillaria species present in the woods, A. gallica was consistently the first to colonize tree stumps that had been coppiced
the previous year. Fractal geometry has been used to model the branching patterns of the hyphae of various Armillaria species. Compared to a strongly pathogenic species like A. solidipes, A. gallica has a relatively sparse branching pattern that is thought to be "consistent with a foraging strategy in which acceptable food bases may be encountered at any distance, and which favours broad and divisive distribution of potential inoculum." Because the rhizomorphs form regular networks
, mathematical concepts of graph theory
have been employed to describe fungal growth and interpret ecological strategies, suggesting that the specific patterns of network attachments allow the fungus "to respond opportunistically to spatially and temporally changing environments".
Armillaria gallica may itself be parasitized by other soil flora
. Several species of the fungus Trichoderma
, including Trichoderma polysporum, T. harzianum
and T. viride
, are able to attack and penetrate and the outer tissue of A. gallica rhizomorphs and parasitize the internal hyphae. The infected rhizomorphs become devoid of living hyphae about one week after the initial infection. Entoloma abortivum
is another fungus that can live parasitically upon A. gallica. The whitish-gray malformed fruit bodies that may result are due to the E. abortivum hyphae penetrating the mushroom and disrupting its normal development.
Physalacriaceae
Physalacriaceae are a family of fungi in the order Agaricales. Species in the genus have a widespread distribution, but most are found in the tropics, particularly in South-East Asia and Australasia. Molecular studies suggested that Physalacria, formerly the sole genus in this family, is related to...
family of the Agaricales
Agaricales
The fungal order Agaricales, also known as gilled mushrooms , or euagarics, contains some of the most familiar types of mushrooms. The order has 33 extant families, 413 genera, and over 13000 described species, along with five extinct genera known only from the fossil record...
order. The species is a common and ecologically important wood-decay fungus
Wood-decay fungus
A wood-decay fungus is a variety of fungus that digests moist wood, causing it to rot. Some wood-decay fungi attack dead wood, such as brown rot, and some, such as Armillaria , are parasitic and colonize living trees. Fungi that not only grow on wood but actually cause it to decay, are called...
that can live as a saprobe, or as an opportunistic parasite
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
in weakened tree hosts to cause root
Root rot
Root rot is a condition found in both indoor and outdoor plants, although more common in indoor plants with poor drainage. As the name states, the roots of the plant rot. Usually, this is a result of overwatering. In houseplants, it is a very common problem, and is slightly less common in outdoor...
or butt rot
Butt rot
thumb|Butt rot of palm, caused by [[Ganoderma zonatum]]Butt rot is a disease of plants, mostly trees, caused by fungi. The fungus attacks the moist, poorly protected undersurface of tree trunk's thickest part , where the end of the stem makes contact with the soil. It may affect the roots as...
. It has a widespread distribution, being found in temperate regions of Asia, North America, and Europe, and forms fruit bodies
Basidiocarp
In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...
singly or in groups in soil or rotting wood. The fungus has been inadvertently introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
to South Africa. Armillaria gallica has had a confusing taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
, 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
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
living in a Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....
forest was reported to cover an area of 15 hectares (37.1 acre), weigh at least 9500 kilograms (20,943.9 lb), and be 1,500 years old. This individual is popularly known as the "humungous fungus", and is a tourist attraction and inspiration for an annual mushroom-themed festival in Crystal Falls
Crystal Falls, Michigan
-Demographics:As of the census of 2000, there were 1,791 people, 795 households, and 470 families residing in the city. The population density was 530.6 per square mile . There were 913 housing units at an average density of 270.5 per square mile...
.
Armillaria gallica is a largely subterranean fungus, and it produces fruit bodies that are up to about 10 cm (3.9 in) in diameter, yellow-brown, and covered with small scales. On the underside of the caps
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
are gills that are white to creamy or pale orange. The stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
may be up to 10 cm (3.9 in) long, with a white cobwebby ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
that divides the color of the stem into pale orange to brown above, and lighter-colored below. The fungus can develop an extensive system of underground root-like structures, called rhizomorphs, that help it to efficiently decompose dead wood in temperate broadleaf and mixed forests
Temperate broadleaf and mixed forests
Mixed forests are a temperate and humid biome. The typical structure of these forests includes four layers. The uppermost layer is the canopy composed of tall mature trees ranging from 33 to 66 m high. Below the canopy is the three-layered, shade-tolerant understory that is roughly 9 to...
. It has been the subject of considerable scientific research due to its importance as a plant pathogen, its ability to bioluminesce
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
, its unusual life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
, and its ability to form large and long-lived colonies
Clonal colony
A clonal colony or genet is a group of genetically identical individuals that have grown in a given location, all originating vegetatively from a single ancestor. In plants, an individual in such a population is referred to as a ramet...
.
Phylogeny, taxonomy and naming
Confusion has surrounded the nomenclatureBinomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...
and taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
of the species now known as Armillaria gallica, paralleling that surrounding the genus Armillaria. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Armillaria mellea
Armillaria mellea
Armillaria mellea is a plant pathogen and a species of Honey fungus. It causes Armillaria root rot in many plant species. The mushrooms are edible but some people may be intolerant to them. The fungus produces mushrooms around the base of trees it has infected...
, was until the 1970s believed to be a pleiomorphic species with a wide distribution, variable pathogenicity, and one of the broadest host
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
ranges known for the fungi. In 1973, Veikko Hintikka reported a technique to distinguish between Armillaria species by growing them together as single spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
isolates on petri dish
Petri dish
A Petri dish is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells or small moss plants. It was named after German bacteriologist Julius Richard Petri, who invented it when working as an assistant to Robert Koch...
es and observing changes in the morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of the cultures. Using a similar technique, Kari Korhonen
Kari Korhonen
Kari Korhonen is a Finnish cartoonist known for his stories about Donald Duck.- References :...
showed in 1978 that the European Armillaria mellea species complex
Species complex
A species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...
could be separated into five reproductively isolated species, which he named "European Biological Species" (EBS) A through E. About the same time, the North American A. mellea was shown to be ten different species (North American Biological Species, or NABS I through X); NABS VII was demonstrated shortly after to be the same species as EBS E. Because several research groups had worked with this widely distributed species, it was assigned several different names.
The species that Korhonen called EBS B was named A. bulbosa by Helga Marxmüller in 1982, as it was thought to be equivalent to Armillaria mellea var. bulbosa, first described by Joseph Barla in 1887, and later raised to species status by Josef Velenovský in 1927. In 1973, the French mycologist Henri Romagnesi
Henri Romagnesi
Henri Charles Louis Romagnesi was a French mycologist who was notable for a thorough review and monograph of the agaric genus Entoloma , as well as extensive work on the large genus Russula, of which he described several new species.-References:...
, unaware of Velenovský's publication, published a description of the species he called Armillariella bulbosa, based on specimens he had found near Compiègne
Compiègne
Compiègne is a city in northern France. It is designated municipally as a commune within the département of Oise.The city is located along the Oise River...
and Saint-Sauveur-le-Vicomte
Saint-Sauveur-le-Vicomte
Saint-Sauveur-le-Vicomte is a commune in the Manche department in Normandy in north-western France.It is situated in the Cotentin Peninsula near Valognes in the Manche département.Population : 2,242 .-History:...
in France. These specimens were later demonstrated to be the same species as the EBS E of Korhonen; EBS B was later determined to be A. cepistipes
Armillaria cepistipes
Armillaria cepistipes is a species of mushroom in the Physalacriaceae family. This is a weakly plant pathogenic species that is typically found growing at the base of deciduous trees that have previously been stressed by another pathogen....
. Therefore, the name A. bulbosa was a misapplied name for EBS E. In 1987 Romagnesi and Marxmüller renamed EBS E to Armillaria gallica. Another synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
, A. lutea, had originally been described by Claude Casimir Gillet
Claude Casimir Gillet
Claude Casimir Gillet, born 19 May 1806, died 1896, was a French botanist and mycologist. He initially trained as a medical doctor and veterinarian.-Publications:* Claude-Casimir Gillet, * Claude-Casimir Gillet, , 230 pp...
in 1874, and proposed as a name for EBS E. Although the name had priority
Principle of Priority
thumb|270px|Boa manditraIn zoology, the scientific study of animals, the Principle of Priority is one of the guiding principles of the International Code of Zoological Nomenclature, defined by Article 23....
due to its early publication date, it was rejected as a nomen ambiguum because of a lack of supporting evidence to identify the fungus, including a specimen, type locality, and incomplete collection notes. A. inflata (Velenovský, 1920) may represent another synonym, but the type specimens were not preserved, so it is considered a dubious name (nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
). As of 2010, both the Index Fungorum
Index Fungorum
Index Fungorum, an international project to index all formal names in the Fungi Kingdom. Somewhat comparable to the IPNI, but with more contributing institutions....
and MycoBank
MycoBank
MycoBank is an online database, documenting new mycological names and combinations, eventually combined with descriptions and illustrations. It is run by the Centraalbureau voor Schimmelcultures fungal biodiversity center in Utrecht....
consider Armillaria gallica Marxm. & Romagn. to be the current name, with A. bulbosa and A. lutea as synonyms.
Phylogenetic analysis of North American Armillaria species based on analysis of amplified fragment length polymorphism
Amplified fragment length polymorphism
Amplified Fragment Length Polymorphism PCR is a PCR-based tool used in genetics research, DNA fingerprinting, and in the practice of genetic engineering. Developed in the early 1990s by Keygene, AFLP uses restriction enzymes to digest genomic DNA, followed by ligation of adaptors to the sticky...
data suggests that A. gallica is most closely related to A. sinapina, A. cepistipes, and A. calvescens. These results are similar to those reported in 1992 that compared sequences of nuclear ribosomal DNA
Ribosomal DNA
Ribosomal DNA codes for ribosomal RNA. The ribosome is an intracellular macromolecule that produces proteins or polypeptide chains. The ribosome itself consists of a composite of proteins and RNA. As shown in the figure, rDNA consists of a tandem repeat of a unit segment, an operon, composed of...
.
The specific epithet gallica is botanical Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "French" (from Gallia, "Gaul"), and refers to the type locality. The prior name bulbosa is Latin for "bulb-bearing, bulbous" (from bulbus and the suffix -osa). Armillaria is derived from the Latin armilla, or "bracelet".
Description
The fruit bodiesBasidiocarp
In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...
of Armillaria gallica have caps
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
that are 2.5 – broad, and depending on their age, may range in shape from conical to convex to flattened. The caps are brownish-yellow to brown when moist, often with a darker-colored center; the color tends to fade upon drying. The cap surface is covered with slender fibers (same color as the cap) that are erect, or sloping upwards.
When the fruit bodies are young, the underside of the caps have a cottony layer of tissue stretching from the edge of the cap to the stem—a partial veil
Partial veil
thumb|150px|right|Developmental stages of [[Agaricus campestris]] showing the role and evolution of a partial veilPartial veil is a mycological term used to describe a temporary structure of tissue found on the fruiting bodies of some basidiomycete fungi, typically agarics...
—which serves to protect the developing gills. As the cap grows in size the membrane is eventually pulled away from the cap to expose the gills. The gills have an adnate (squarely attached) to somewhat decurrent (extending down the length of the stem) attachment to the stem. They are initially white, but age to a creamy or pale orange covered with rust-colored spots. The stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
is 4 – long and 0.6 – thick, and almost club-shaped with the base up to 1.3 – thick. Above the level of the ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
, the stem is pale orange to brown, while below it is whitish or pale pink, becoming grayish-brown at the base. The ring is positioned about 0.4 – below the level of the cap, and may be covered with yellowish to pale-brownish woolly cottony mycelia
Mycelium
thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...
. The base of the stem is attached to rhizomorphs, black root-like structures 1–3 mm in diameter. While the primary function of the below-ground mycelia is to absorb nutrients from the soil, the rhizomorphs serve a more exploratory function, to locate new food bases.
Microscopic features
When the spores are seen in deposit, such as with a spore printSpore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
, they appear whitish. They have an ellipsoid or oblong shape, usually contain an oil droplet, and have dimensions of 7–8.5 by 5–6 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
. The spore-bearing cells, the basidia
Basidium
thumb|right|500px|Schematic showing a basidiomycete mushroom, gill structure, and spore-bearing basidia on the gill margins.A basidium is a microscopic, spore-producing structure found on the hymenophore of fruiting bodies of basidiomycete fungi. The presence of basidia is one of the main...
, are club-shaped, four-spored (rarely two-spored), and measure 32–43 by 7–8.7 µm. Other cells present in the fertile hymenium
Hymenium
The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia or...
include the cheilocystidia (cystidia
Cystidium
A cystidium is a relatively large cell found on the hymenium of a basidiomycete , often between clusters of basidia. Since cystidia have highly varied and distinct shapes that are often unique to a particular species or genus, they are a useful micromorphological characteristic in the...
present on the edge of a gill), which are club-shaped, roughly cylindrical and 15–25 by 5.0–12 µm. Cystidia are also present on the stem (called caulocystidia), and are broadly club-shaped, measuring 20–55 by 11–23 µm. The cap cuticle
Pileipellis
thumb|300px||right|The cuticle of some mushrooms, such as [[Russula mustelina]] shown here, can be peeled from the cap, and may be useful as an identification feature....
is made of hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e that are irregularly interwoven and project upward to form the scales seen on the surface. The hyphae that make up the surface scales typically measure 26–88 µm long by 11–27 µm thick and can be covered with a crust of pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
. Clamp connection
Clamp connection
A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...
s are present in the hyphae of most tissues.
Edibility
Like all Armillaria species, A. gallica is considered edible. Thorough cooking is usually recommended, as the raw mushroom tastes acrid when fresh or undercooked. One author advises to consume only a small portion initially, as some people may experience an upset stomach. The taste is described as "mild to bitter", and the odor "sweet", or reminiscent of camembertCamembert
Camembert is a commune in the Orne department in north-western France.It is most famous as the place where camembert cheese originated.Camembert has been called "The largest small village in France." This is because the area of the commune itself is out of proportion to the center of the village...
cheese.
Similar species
Armillaria calvescensArmillaria calvescens
Armillaria calvescens is a species of mushroom in the Physalacriaceae family. Similar in appearance to Armillaria gallica, this species is often found on maple in Canada and New England, as well as other hardwoods in the western United States....
is rather similar in appearance, and can only be reliably distinguished from A. gallica by observing microscopic characteristics. A. calvescens has a more northern distribution, and in North America, is rarely found south of the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
. A. mellea
Armillaria mellea
Armillaria mellea is a plant pathogen and a species of Honey fungus. It causes Armillaria root rot in many plant species. The mushrooms are edible but some people may be intolerant to them. The fungus produces mushrooms around the base of trees it has infected...
has a thinner stem than A. gallica, but can be more definitively distinguished by the absence of clamps at the base of the basidia. Similarly, A. cepistipes and A. gallica are virtually identical in appearance (especially older fruit bodies), and are identified by differences in geographical distribution, host range, and microscopic characteristics. Molecular
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
methods have been developed to discriminate between the two species by comparing DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
s in the gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
coding translation elongation factor 1-alpha.
Metabolites
Armillaria gallica can produce cyclobutaneCyclobutane
Cyclobutane is an organic compound with the formula 4. Cyclobutane is a colourless gas and commercially available as a liquefied gas. Derivatives of cyclobutane are called cyclobutanes...
-containing metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
s such as arnamiol, a natural product
Natural product
A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...
that is classified as a sesquiterpenoid
Terpenoid
The terpenoids , sometimes called isoprenoids, are a large and diverse class of naturally occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures that differ from one another not only in...
aryl
Aryl
In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....
ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
. Although the specific function of arnamiol is not definitively known, similar chemicals present in other Armillaria species are thought to play a role in inhibiting the growth of antagonistic bacteria or fungi, or in killing cells of the host plant prior to infection.
Bioluminescence
The mycelia (but not the fruit bodiesBasidiocarp
In fungi, a basidiocarp, basidiome or basidioma , is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not produce such structures...
) of Armillaria gallica are known to be bioluminescent. Experiments have shown that the intensity of the luminescence is enhanced when the mycelia are disturbed during growth or when they are exposed to fluorescent light. Bioluminescence is caused by the action of luciferase
Luciferase
Luciferase is a generic term for the class of oxidative enzymes used in bioluminescence and is distinct from a photoprotein. One famous example is the firefly luciferase from the firefly Photinus pyralis. "Firefly luciferase" as a laboratory reagent usually refers to P...
s, enzymes that produce light by the oxidation of a luciferin
Luciferin
Luciferins are a class of light-emitting biological pigments found in organisms that cause bioluminescence...
(a pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
). The biological purpose of bioluminescence in fungi is not definitively known, although several hypotheses have been suggested: it may help attract insects to help with spore dispersal, it may be a by-product of other biochemical functions, or it may help deter heterotroph
Heterotroph
A heterotroph is an organism that cannot fix carbon and uses organic carbon for growth. This contrasts with autotrophs, such as plants and algae, which can use energy from sunlight or inorganic compounds to produce organic compounds such as carbohydrates, fats, and proteins from inorganic carbon...
s that might consume the fungus.
Humongous fungus
Researchers reported finding Armillaria gallica in the Upper Peninsula of MichiganUpper Peninsula of Michigan
The Upper Peninsula of Michigan is the northern of the two major land masses that make up the U.S. state of Michigan. It is commonly referred to as the Upper Peninsula, the U.P., or Upper Michigan. It is also known as the land "above the Bridge" linking the two peninsulas. The peninsula is bounded...
in the early 1990s, during an unrelated research project to study the possible biological effects of extremely low frequency
Extremely low frequency
Extremely low frequency is a term used to describe radiation frequencies from 3 to 300 Hz. In atmosphere science, an alternative definition is usually given, from 3 Hz to 3 kHz...
radio stations, which were being investigated as a means to communicate with submerged submarines. In one particular forest stand, Armillaria-infected oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
trees had been harvested, and their stumps were left to rot in the field. Later, when red pines were planted in the same location, the seedlings were killed by the fungus, identified as A. gallica (then known as A. bulbosa). Using molecular genetics
Molecular genetics
Molecular genetics is the field of biology and genetics that studies the structure and function of genes at a molecular level. The field studies how the genes are transferred from generation to generation. Molecular genetics employs the methods of genetics and molecular biology...
, they determined that the underground mycelia
Mycelium
thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...
of one individual fungal colony
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
covered 15 ha (37.1 acre), weighing over 9500 kilograms (20,943.9 lb), with an estimated age of 1,500 years. The analysis used restriction fragment length polymorphism
Restriction fragment length polymorphism
In molecular biology, restriction fragment length polymorphism, or RFLP , is a technique that exploits variations in homologous DNA sequences. It refers to a difference between samples of homologous DNA molecules that come from differing locations of restriction enzyme sites, and to a related...
(RFLP) and random amplification of polymorphic DNA
RAPD
RAPD stands for random amplification of polymorphic DNA. It is a type of PCR reaction, but the segments of DNA that are amplified are random. The scientist performing RAPD creates several arbitrary, short primers , then proceeds with the PCR using a large template of genomic DNA, hoping that...
(RAPD) to examine isolates
Genetic isolate
A genetic isolate is population of organisms that has little genetic mixing with other organisms within the same species. This may result in speciation, but this is not necessarily the case...
collected from fruit bodies and rhizomorphs (underground aggregations of fungal cells that resemble plant roots) along 1 kilometre (0.621372736649807 mi) transect
Transect
A transect is a path along which one records and counts occurrences of the phenomena of study .It requires an observer to move along a fixed path and to count occurrences along the path and, at the same time, obtain the distance of the object from the path...
s in the forest. The 15-hectare area yielded isolates that had identical mating type
Mating type
Mating types occur in eukaryotes that undergo sexual reproduction via isogamy. Since the gametes of different mating types look alike, they are often referred to by numbers, letters, or simply "+" and "-" instead of "male" and "female." Mating can only take place between different mating...
alleles and mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
restriction fragment
Restriction fragment
A restriction fragment is a DNA fragment resulting from the cutting of a DNA strand by a restriction enzyme , a process called restriction. Each restriction enzyme is highly specific, recognising a particular short DNA sequence, or restriction site, and cutting both DNA strands at specific points...
patterns; this degree of genetic similarity indicated that the samples were all derived from a single genetic individual, or clone
Clone (cell biology)
A clone is a group of identical cells that share a common ancestry, meaning they are derived from the same mother cell.Clonality implies the state of a cell or a substance being derived from one source or the other...
, that had reached its size through vegetative growth
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...
. In their conclusion the authors noted: "This is the first report estimating the minimum size, mass, and age of an unambiguously defined fungal individual. Although the number of observations for plants and animals is much greater, members of the fungal kingdom should now be recognized as among the oldest and largest organisms on earth." After the Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
paper was published, major media outlets from around the world visited the site where the specimens were found; as a result of this publicity, the individual acquired the common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
"humongous fungus". There was afterward some scholarly debate as to whether the fungus qualified to be considered in the same category as other large organisms such as the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....
or the giant redwood.
The fungus has since become a popular tourist attraction in Michigan, and has inspired a "Humongous Fungus Fest" held annually in August in Crystal Falls
Crystal Falls, Michigan
-Demographics:As of the census of 2000, there were 1,791 people, 795 households, and 470 families residing in the city. The population density was 530.6 per square mile . There were 913 housing units at an average density of 270.5 per square mile...
. The organism was the subject of a Late Show Top Ten List on Late Night with David Letterman
Late Night with David Letterman
Late Night with David Letterman is a nightly hour-long comedy talk show on NBC that was created and hosted by David Letterman. It premiered in 1982 as the first incarnation of the Late Night franchise and went off the air in 1993, after Letterman left NBC and moved to Late Show on CBS. Late Night...
, and an advertising campaign by the rental company U-Haul
U-Haul
U-Haul International, Inc. is an American equipment rental company, based in Phoenix, Arizona, that has been in operation since 1945. The company was founded by Leonard Shoen U-Haul International, Inc. is an American equipment rental company, based in Phoenix, Arizona, that has been in operation...
.
Life cycle and growth
The life cycleBiological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
of A. gallica includes two diploidization–haploidization events. The first of these is the usual process of cell fusion
Karyogamy
Karyogamy is the fusion of pronuclei of two cells, as part of syngamy, fertilization, or true bacterial conjugation.It is one of the two major modes of reproduction in fungi...
(forming a diploid) followed by meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
during the formation of haploid basidiospore
Basidiospore
A basidiospore is a reproductive spore produced by Basidiomycete fungi. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. In grills under a cap of one common species in the phylum of...
s. The second event is more cryptic, and occurs before fruit body formation. In most basidiomycetous fungi, the hyphae of compatible mating type
Mating type
Mating types occur in eukaryotes that undergo sexual reproduction via isogamy. Since the gametes of different mating types look alike, they are often referred to by numbers, letters, or simply "+" and "-" instead of "male" and "female." Mating can only take place between different mating...
s will fuse to form a two-nucleate
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
, or dikaryotic stage; this stage is not observed in Armillaria species, which have cells that are mostly monokaryotic and diploid. Genetic analyses suggest that the dikaryotic mycelia undergo an extra haploidization event prior to fruit body formation to create a genetic mosaic. These regular and repeating haploidization events result in increased genetic diversity
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
, which helps the fungus to adapt to unfavorable changes in environmental conditions, like drought.
The growth rate of A. gallica rhizomorphs is between 0.3 and 0.6 m (0.984251968503937 and 2 ft) per year. Population genetic
Population genetics
Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...
studies of the fungus conducted in the 1990s demonstrated that genetic individuals grow mitotically
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
from a single point of origin to eventually occupy territories that may include many adjacent root systems over large areas (several hectare
Hectare
The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
s) of forest floor. Based on the low mutation rate
Mutation rate
In genetics, the mutation rate is the chance of a mutation occurring in an organism or gene in each generation...
s observed in large, long-lived individuals, A. gallica appears to have an especially stable genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
. It has also been hypothesized that genetic stability may result from self-renewing mycelial repositories of nuclei with stem cell
Stem cell
This article is about the cell type. For the medical therapy, see Stem Cell TreatmentsStem cells are biological cells found in all multicellular organisms, that can divide and differentiate into diverse specialized cell types and can self-renew to produce more stem cells...
-like properties.
Habitat and distribution
Armillaria gallica can normally be found on the ground, but sometimes on stumps and logs. Mushrooms that appear to be terrestrial are attached to plant roots underneath the surface. It is widely distributed and has been collected in North America, Europe, and Asia (China, Iran, and Japan). The species has also been found in the Western CapeWestern Cape
The Western Cape is a province in the south west of South Africa. The capital is Cape Town. Prior to 1994, the region that now forms the Western Cape was part of the much larger Cape Province...
Province of South Africa, where it is thought to have been introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
from potted plants imported from Europe during the early colonization of Cape Town. In Scandinavia, it is absent in areas with very cold climates, like Finland or Norway, but it is found in southern Sweden. It is thought to be the most prevalent low altitude species of Armillaria in Great Britain and France. The upper limits of its altitude vary by region. In the French Massif Central
Massif Central (geology)
The Massif Central forms together with the Armorican Massif one of the two big basement massifs in France. Its geological evolution started in the late Neoproterozoic and continues to this day. It has been shaped mainly by the Caledonian orogeny and the Variscan orogeny. The Alpine orogeny has...
, it is found up to 1100 m (3,608.9 ft), while in Bavaria, which has a more continental climate
Continental climate
Continental climate is a climate characterized by important annual variation in temperature due to the lack of significant bodies of water nearby...
, the upper limit of distribution reaches 600 m (1,968.5 ft). In Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...
n forests, it is the most common Armillaria between elevations of 70 to 1450 m (229.7 to 4,757.2 ft). Field studies suggest that A. gallica prefers sites that are low in organic matter
Organic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
and have high soil pH
Soil pH
The soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
s.
In North America, it is common east of the Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
, but rare in the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
. In California, where it is widely distributed, the fungus is found in a variety of plant communities, including aspen, coastal oak woodland, Douglas Fir, Klamath mixed conifer
Klamath National Forest
Klamath National Forest is a national forest, in the Klamath Mountains, located in Siskiyou County in northern California, but with a tiny extension into southern Jackson County in Oregon. The forest contains continuous stands of ponderosa pine, Jeffrey pine, Douglas fir, red fir, white fir and...
, montane hardwood, montane hardwood-conifer, montane riparian
Riparian zone
A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth. Plant habitats and communities along the river margins and banks are called riparian vegetation, characterized by...
, Redwood, Sierran mixed conifer, valley oak
Valley Oak
Quercus lobata, commonly called the Valley oak, grows into the largest of North American oaks. It is endemic to California, growing in the interior valleys and foothills. Mature specimens may attain an age of up to 600 years. This deciduous oak requires year-round access to groundwater.Its thick,...
woodland, valley-foothill riparian, and White Fir
White Fir
White Fir is a fir native to the mountains of western North America, occurring at altitudes of 900-3,400 m. It is a medium to large evergreen coniferous tree growing to 25–60 m tall and with a trunk diameter of up to 2 m . It is popular as an ornamental landscaping tree and as a Christmas Tree...
. It was found to be the most common Armillaria species in hardwood and mixed oak forests in western Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
.
A Chinese study published in 2001 used the molecular biological
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
technique restriction fragment length polymorphism
Restriction fragment length polymorphism
In molecular biology, restriction fragment length polymorphism, or RFLP , is a technique that exploits variations in homologous DNA sequences. It refers to a difference between samples of homologous DNA molecules that come from differing locations of restriction enzyme sites, and to a related...
to analyze the differences in DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
between 23 A. gallica specimens collected from the Northern Hemisphere. The results suggest that based on the restriction fragment length polymorphism patterns observed, there are four global A. gallica subpopulations: the Chinese, European, North American–Chinese, and North American–European geographical lineages
Lineage (evolution)
An evolutionary lineage is a sequence of species, that form a line of descent, each new species the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics.-...
. A 2007 study on the northeastern and southwestern Chinese distribution of Armillaria, using fruit body and pure culture morphology, concluded that there are several unnamed species (Chinese biological species C, F, H, J and L) that are similar to the common A. gallica.
Ecology
Root rot
Root rot is a condition found in both indoor and outdoor plants, although more common in indoor plants with poor drainage. As the name states, the roots of the plant rot. Usually, this is a result of overwatering. In houseplants, it is a very common problem, and is slightly less common in outdoor...
or butt rot
Butt rot
thumb|Butt rot of palm, caused by [[Ganoderma zonatum]]Butt rot is a disease of plants, mostly trees, caused by fungi. The fungus attacks the moist, poorly protected undersurface of tree trunk's thickest part , where the end of the stem makes contact with the soil. It may affect the roots as...
. As the diseased trees die, the wood dries, increasing the chance of catching fire after being struck by lightning. The resulting forest fire may in turn kill the species that killed the trees. Plants that are under water stress
Water stress
Researchers define water stress and water scarcity in different ways. For example, some have presented maps showing the physical existence of water in nature to show nations with lower or higher volumes of water available for use. Others have related water availability to population...
caused by dry soils or waterlogging
Waterlogging (agriculture)
Waterlogging refers to the saturation of soil with water. Soil may be regarded as waterlogged when the water table of the groundwater is too high to conveniently permit an anticipated activity, like agriculture....
are more susceptible to infection by A. gallica. It has been shown to be one of several Armillaria species responsible for widespread mortality of oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
trees in the Arkansas Ozarks. The fungus has also been shown to infect Daylily
Daylily
Daylily is the general nonscientific name of a species, hybrid or cultivar of the genus Hemerocallis . Daylily cultivar flowers are highly diverse in colour and form, as a result of hybridization efforts of gardening enthusiasts and professional horticulturalists...
in South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
, Northern highbush blueberry
Northern highbush blueberry
Northern highbush blueberry, Vaccinium corymbosum, is a species of blueberry native to eastern North America, from Nova Scotia and Ontario south to Alabama, and west to Wisconsin...
(Vaccinium corymbosum) in Italy and vineyards (Vitis
Vitis
Vitis is a genus of about 60 species of vining plants in the flowering plant family Vitaceae. The genus is made up of species predominantly from the Northern hemisphere. It is economically important as the source of grapes, both for direct consumption of the fruit and for fermentation to produce...
species) of Rías Baixas
Rías Baixas (DO)
Rías Baixas is a Spanish Denominación de Origen for wines located in the province of Pontevedra and the south of the province of A Coruña in the autonomous community of Galicia, Spain...
in northwestern Spain. The latter infestation "may be related to the fact that the vineyards from which they were isolated were located on cleared forestry sites". When A. solidipes and A. gallica co-occur in the same forest, infection of root systems by A. gallica may reduce damage or prevent infection from A. solidipes.
Armillaria gallica can develop an extensive subterranean system of rhizomorphs, which helps it to compete with other fungi for resources or to attack trees weakened by other fungi. A field study in an ancient broadleaved woodland in England showed that of five Armillaria species present in the woods, A. gallica was consistently the first to colonize tree stumps that had been coppiced
Coppicing
Coppicing is a traditional method of woodland management which takes advantage of the fact that many trees make new growth from the stump or roots if cut down. In a coppiced wood, young tree stems are repeatedly cut down to near ground level...
the previous year. Fractal geometry has been used to model the branching patterns of the hyphae of various Armillaria species. Compared to a strongly pathogenic species like A. solidipes, A. gallica has a relatively sparse branching pattern that is thought to be "consistent with a foraging strategy in which acceptable food bases may be encountered at any distance, and which favours broad and divisive distribution of potential inoculum." Because the rhizomorphs form regular networks
Network theory
Network theory is an area of computer science and network science and part of graph theory. It has application in many disciplines including statistical physics, particle physics, computer science, biology, economics, operations research, and sociology...
, mathematical concepts of graph theory
Graph theory
In mathematics and computer science, graph theory is the study of graphs, mathematical structures used to model pairwise relations between objects from a certain collection. A "graph" in this context refers to a collection of vertices or 'nodes' and a collection of edges that connect pairs of...
have been employed to describe fungal growth and interpret ecological strategies, suggesting that the specific patterns of network attachments allow the fungus "to respond opportunistically to spatially and temporally changing environments".
Armillaria gallica may itself be parasitized by other soil flora
Soil life
Soil life or soil biota is a collective term for all the organisms living within the soil.-Overview:In balanced soil, plants grow in an active and steady environment. The mineral content of the soil and its heartiful structure are important for their well-being, but it is the life in the earth that...
. Several species of the fungus Trichoderma
Trichoderma
Trichoderma is a genus of fungi that is present in all soils, where they are the most prevalent culturable fungi. Many species in this genus can be characterized as opportunistic avirulent plant symbionts.-Species:...
, including Trichoderma polysporum, T. harzianum
Trichoderma harzianum
Trichoderma harzianum is a fungus that is also used as a fungicide. It is used for foliar application, seed treatment and soil treatment for suppression of various disease causing fungal pathogens. Commercial biotechnological products such as 3Tac have been useful for treatment of Botrytis,...
and T. viride
Trichoderma viride
Trichoderma viride is a fungus and a biofungicide.It is used for seed and soil treatment for suppression of various diseases caused by fungal pathogens. It is also a pathogen in its own right, causing green mould rot of onion.-Biology:...
, are able to attack and penetrate and the outer tissue of A. gallica rhizomorphs and parasitize the internal hyphae. The infected rhizomorphs become devoid of living hyphae about one week after the initial infection. Entoloma abortivum
Entoloma abortivum
Entoloma abortivum, commonly known as the aborted entoloma, is an edible mushroom in the Entolomataceae family of fungi. 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....
is another fungus that can live parasitically upon A. gallica. The whitish-gray malformed fruit bodies that may result are due to the E. abortivum hyphae penetrating the mushroom and disrupting its normal development.