Lactarius indigo
Encyclopedia
Lactarius indigo, commonly known as the indigo milk cap, the indigo (or blue) Lactarius, or the blue milk mushroom, is a species of fungus
in the Russulaceae
family of mushroom
s. A widely distributed species, it grows naturally in eastern North America, East Asia, and Central America; it has also been reported from southern France. L. indigo grows on the ground in both deciduous
and coniferous forests, where it forms mycorrhiza
l associations with a broad range of trees. The fruit body
color ranges from dark blue in fresh specimens to pale blue-gray in older ones. The milk, or latex
, that oozes when the mushroom tissue is cut or broken—a feature common to all members of the Lactarius
genus—is also indigo
blue, but slowly turns green upon exposure to air. The cap
is typically between 5 to 15 cm (2 to 5.9 ) broad, and the stem
2 to 8 cm (0.78740157480315 to 3.1 in) tall by 1 to 2.5 cm (0.393700787401575 to 0.984251968503937 in) thick. It is an edible mushroom
, and is sold in rural markets in Mexico, Guatemala, and China.
. German botanist Otto Kuntze
called it Lactifluus indigo in his 1891 treatise Revisio Generum Plantarum
, but the suggested name change was not adopted by others. Hesler
and Smith in their 1960 study of North American species of Lactarius defined L. indigo as the type species
of subsection Caerulei, a group characterized by blue latex and a sticky, blue cap. In 1979, they revised their opinions on the organization of subdivisions in the genus Lactarius, and instead placed L. indigo in subgenus
Lactarius based on the color of latex, and the subsequent color changes observed after exposure to air. As they explained:
The specific epithet indigo is derived from the Latin
word meaning "indigo blue". Its names in the English vernacular
include the "indigo milk cap", the "indigo Lactarius", the "blue milk mushroom", and the "blue Lactarius". In central Mexico, it is known as añil, azul, hongo azul, zuin, and zuine; it is also called quexque (meaning "blue") in Veracruz
and Puebla
.
, a mass of threadlike fungal cells called hypha
e that make up the bulk of the organism. Under appropriate environmental conditions of temperature, humidity, and nutrient availability, the visible reproductive structures (fruit bodies
) are formed. The cap
of the fruit body, measuring between 5 – in diameter, is initially convex and later develops a central depression; in age it becomes even more deeply depressed, becoming somewhat funnel-shaped as the edge of the cap lifts upward. The margin of the cap is rolled inwards when young, but unrolls and elevates as it matures. The cap surface is indigo blue when fresh, but fades to a paler grayish- or silvery-blue, sometimes with greenish splotches. It is often zonate: marked with concentric lines that form alternating pale and darker zones, and the cap may have dark blue spots, especially towards the edge. Young caps are sticky to the touch.The flesh
is pallid to bluish in color, slowly turning greenish after being exposed to air; its taste is mild to slightly acrid. The flesh of the entire mushroom is brittle, and the stem, if bent sufficiently, will snap open cleanly. The latex exuded from injured tissue is indigo
blue, and stains the wounded tissue greenish; like the flesh, the latex has a mild taste. Lactarius indigo is noted for not producing as much latex as other Lactarius species, and older specimens in particular may be too dried out to produce any latex.
The gills of the mushroom range from adnate (squarely attached to the stem) to slightly decurrent (running down the length of the stem), and crowded close together. Their color is an indigo blue, becoming paler with age or staining green with damage. The stem
is 2 – tall by 1 – thick, and the same diameter throughout or sometimes narrowed at base. Its color is indigo blue to silvery- or grayish blue. The interior of the stem is solid and firm initially, but develops a hollow with age. Like the cap, it is initially sticky or slimy to the touch when young, but soon dries out. Its attachment to the cap is usually in a central position, although it may also be off-center. Fruit bodies of L. indigo have no distinguishable odor.
Lactarius indigo var. diminutivus (the "smaller indigo milk cap") is a smaller variant of the mushroom, with a cap diameter between 3 –, and a stem that is 1.5 – long and 0.3 – thick. It is often seen in Virginia
. Hesler and Smith, who first described the variant based on specimens found in Brazoria County, Texas
, described its typical habitat as "along [the] sides of a muddy ditch under grasses and weeds, [with] loblolly pine
nearby".
, the spores
appear cream to yellow colored. Viewed with a light microscope, the spores are translucent (hyaline
), elliptical to nearly spherical in shape, with amyloid
warts, and have dimensions of 7–9 by 5.5–7.5 µm
. Scanning electron microscopy reveals reticulations on the spore surface. The hymenium
is the spore-producing tissue layer of the fruit body, and consists of hypha
e that extend into the gills and terminate as end cells. Various cell types can be observed in the hymenium, and the cells have microscopic characteristics that may be used to help identify or distinguish species in cases where the macroscopic characters may be ambiguous. The spore-bearing cells, the basidia, are 4-spored and measure 37–45 µm long by 8–10 µm wide at the thickest point. Cystidia are terminal cells of hyphae in the hymenium which do not produce spores, and function in aiding spore dispersal, and maintaining favorable humidity around developing spores. The pleurocystidia are cystidia that are found on the face of a gill; they are 40–56 by 6.4–8 µm, roughly spindle-shaped, and have a constricted apex. The cheilocystidia—located on the edge of a gill—are abundant, and are 40–45.6 by 5.6–7.2 µm.
), found in eastern North America, which has a grayish-blue cap when young, but it has reddish-brown to purple-brown latex and gills. L. chelidonium
has a yellowish to dingy yellow-brown to bluish-gray cap and yellowish to brown latex. L. quieticolor
has blue-colored flesh in the cap and orange to red-orange flesh in the base of the stem. Although the blue discoloration of L. indigo is thought to be rare in the genus Lactarius, in 2007 five new species were reported from Peninsular Malaysia
with bluing latex or flesh, including L. cyanescens
, L. lazulinus
, L. mirabilis
, and two species still unnamed.
considers it a "superior edible", while a field guide
on Kansas
fungi rates it as "mediocre in quality". It may have a slightly bitter, or peppery taste, and has a coarse, grainy texture. The firm flesh is best prepared by cutting the mushroom in thin slices. The blue color disappears with cooking, and the mushroom becomes grayish. Because of the granular texture of the flesh, it does not lend itself well to drying. Specimens producing copious quantities of milk may be used to add color to marinades.
In Mexico, individuals harvest the wild mushrooms for sale at farmers' markets, typically from June to November, where they are considered a "second class" species for consumption. L. indigo is also sold in Guatemalan markets from May to October. It is one of thirteen Lactarius species sold at rural markets in Yunnan
in southwestern China.
of Mexican specimens has shown L. indigo to contain 95.1% moisture
, 4.3 mg of fat
per gram of mushroom (mg/g), and 13.4 mg/g protein
. There is 18.7 mg/g of dietary fiber
, much higher in comparison to the common button mushroom, which contains 6.6 mg/g. Compared to three other wild edible mushroom species also tested in the study (Amanita rubescens, Boletus frostii
, and Ramaria flava
), L. indigo contained the highest saturated fatty acids content, including stearic acid
with 32.1 mg/g—slightly over half of the total free fatty acid content.
The blue color of Lactarius indigo is due to (7-isopropenyl-4-methylazulen-1-yl)methyl stearate, an organic compound
known as an azulene
. It is unique to this species, but similar to a compound found in L. deliciosus
.
throughout southern and eastern North America, but is most common along the Gulf Coast and in Mexico. Its frequency of appearance in the Appalachian Mountains
of the United States has been described as "occasional to locally common". Mycologist David Arora
notes that in the United States, the species is found with ponderosa pine
in Arizona
, but is absent in California
's ponderosa pine forests. It has also been collected from China, India, Guatemala, and Costa Rica (in forests dominated by oak). In Europe, it has so far only been found in southern France. A study on the seasonal appearance of fruiting bodies in the subtropical forests of Xalapa
, Mexico, confirmed that maximal production coincided with the rainy season
between June and September.
Lactarius indigo is a mycorrhizal
fungus, and as such, establishes a mutualistic relationship with the roots of certain trees ("hosts"), in which the fungi exchange minerals
and amino acids extracted from the soil for fixed carbon
from the host. The subterranean hyphae of the fungus grow a sheath of tissue around the rootlets of a broad range of tree species, forming so-called ectomycorrhizae—an intimate association that is especially beneficial to the host, as the fungus produces enzyme
s that mineralize
organic compounds and facilitate the transfer of nutrients to the tree.
Reflecting their close relationships with trees, the fruit bodies of Lactarius indigo are typically found growing on the ground, scattered or in groups, in both deciduous
and coniferous forests. They are also commonly found in floodplain
areas that have been recently submerged. In Mexico, associations have been noted with Mexican alder, American Hornbeam, American Hophornbeam
, and Liquidambar macrophylla, while in Guatemala the mushroom associates with Smooth-bark Mexican Pine
and other pine
and oak
species. In Costa Rica
, the species forms associations with several native oaks of the Quercus genus. Under controlled laboratory conditions, L. indigo was shown to be able to form ectomycorrhizal associations with the neotropical pine species Mexican White Pine, Hartweg's Pine, Mexican yellow pine
, Smooth-bark Mexican Pine
, and also with the Eurasia
n pines Aleppo Pine, European Black Pine, Maritime Pine
and Scots Pine
.
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
in the Russulaceae
Russulaceae
The Russulaceae are a family of fungi in the order Russulales. According to a 2008 estimate, the family contains 1243 species. Its species typically have fruit bodies with friable, chalk-like stalks, that break with a distinct crack, somewhat like a carrot but with porous flesh...
family of mushroom
Mushroom
A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...
s. A widely distributed species, it grows naturally in eastern North America, East Asia, and Central America; it has also been reported from southern France. L. indigo grows on the ground in both deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
and coniferous forests, where it forms mycorrhiza
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
l associations with a broad range of trees. The fruit body
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...
color ranges from dark blue in fresh specimens to pale blue-gray in older ones. The milk, or latex
Latex
Latex is the stable dispersion of polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.Latex as found in nature is a milky fluid found in 10% of all flowering plants . It is a complex emulsion consisting of proteins, alkaloids, starches, sugars, oils, tannins, resins,...
, that oozes when the mushroom tissue is cut or broken—a feature common to all members of the Lactarius
Lactarius
Lactarius is a genus of mushroom-producing fungi. The genus, collectively known commonly as milk-caps, are characterized by the fact that they exude a milky fluid if cut or damaged...
genus—is also indigo
Indigo
Indigo is a color named after the purple dye derived from the plant Indigofera tinctoria and related species. The color is placed on the electromagnetic spectrum between about 420 and 450 nm in wavelength, placing it between blue and violet...
blue, but slowly turns green upon exposure to air. The cap
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...
is typically between 5 to 15 cm (2 to 5.9 ) broad, and 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...
2 to 8 cm (0.78740157480315 to 3.1 in) tall by 1 to 2.5 cm (0.393700787401575 to 0.984251968503937 in) thick. It is an edible mushroom
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...
, and is sold in rural markets in Mexico, Guatemala, and China.
Taxonomy and nomenclature
Originally described in 1822 as Agaricus indigo by American mycologist Lewis David de Schweinitz, the species was later transferred to the genus Lactarius in 1838 by the Swede Elias Magnus FriesElias Magnus Fries
-External links:*, Authors of fungal names, Mushroom, the Journal of Wild Mushrooming.*...
. German botanist Otto Kuntze
Otto Kuntze
Otto Carl Ernst Kuntze was a German botanist.-Biography:Otto Kuntze was born in Leipzig.An apothecary in his early career, he published an essay entitled Pocket Fauna of Leipzig. Between 1863 and...
called it Lactifluus indigo in his 1891 treatise Revisio Generum Plantarum
Revisio Generum Plantarum
Revisio Generum Plantarum, also known by its standard botanical abbreviation Revis. Gen. Pl., is a botanic treatise by Otto Kuntze...
, but the suggested name change was not adopted by others. Hesler
Lexemuel Ray Hesler
-External links:* Finding Aid for the Lexemuel Ray Hesler Collection, 1899-1982...
and Smith in their 1960 study of North American species of Lactarius defined L. indigo as 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...
of subsection Caerulei, a group characterized by blue latex and a sticky, blue cap. In 1979, they revised their opinions on the organization of subdivisions in the genus Lactarius, and instead placed L. indigo in subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...
Lactarius based on the color of latex, and the subsequent color changes observed after exposure to air. As they explained:
The gradual development of blue to violet pigmentation as one progresses from species to species is an interesting phenomenon deserving further study. The climax is reached in L. indigo which is blue throughout. L. chelidonium and its variety chelidonioides, L. paradoxus, and L. hemicyaneus may be considered as mileposts along the road to L. indigo.
The specific epithet indigo is derived from the 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...
word meaning "indigo blue". Its names in the English vernacular
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...
include the "indigo milk cap", the "indigo Lactarius", the "blue milk mushroom", and the "blue Lactarius". In central Mexico, it is known as añil, azul, hongo azul, zuin, and zuine; it is also called quexque (meaning "blue") in Veracruz
Veracruz
Veracruz, formally Veracruz de Ignacio de la Llave officially Estado Libre y Soberano de Veracruz de Ignacio de la Llave , is one of the 31 states that, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided in 212 municipalities and its capital city is...
and Puebla
Puebla
Puebla officially Estado Libre y Soberano de Puebla is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 217 municipalities and its capital city is Puebla....
.
Description
Like many other mushrooms, Lactarius indigo develops from a nodule, or pinhead, that forms within the underground myceliumMycelium
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...
, a mass of threadlike fungal cells called 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 make up the bulk of the organism. Under appropriate environmental conditions of temperature, humidity, and nutrient availability, the visible reproductive structures (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...
) are formed. The cap
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...
of the fruit body, measuring between 5 – in diameter, is initially convex and later develops a central depression; in age it becomes even more deeply depressed, becoming somewhat funnel-shaped as the edge of the cap lifts upward. The margin of the cap is rolled inwards when young, but unrolls and elevates as it matures. The cap surface is indigo blue when fresh, but fades to a paler grayish- or silvery-blue, sometimes with greenish splotches. It is often zonate: marked with concentric lines that form alternating pale and darker zones, and the cap may have dark blue spots, especially towards the edge. Young caps are sticky to the touch.The flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....
is pallid to bluish in color, slowly turning greenish after being exposed to air; its taste is mild to slightly acrid. The flesh of the entire mushroom is brittle, and the stem, if bent sufficiently, will snap open cleanly. The latex exuded from injured tissue is indigo
Indigo
Indigo is a color named after the purple dye derived from the plant Indigofera tinctoria and related species. The color is placed on the electromagnetic spectrum between about 420 and 450 nm in wavelength, placing it between blue and violet...
blue, and stains the wounded tissue greenish; like the flesh, the latex has a mild taste. Lactarius indigo is noted for not producing as much latex as other Lactarius species, and older specimens in particular may be too dried out to produce any latex.
The gills of the mushroom range from adnate (squarely attached to the stem) to slightly decurrent (running down the length of the stem), and crowded close together. Their color is an indigo blue, becoming paler with age or staining green with damage. 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 2 – tall by 1 – thick, and the same diameter throughout or sometimes narrowed at base. Its color is indigo blue to silvery- or grayish blue. The interior of the stem is solid and firm initially, but develops a hollow with age. Like the cap, it is initially sticky or slimy to the touch when young, but soon dries out. Its attachment to the cap is usually in a central position, although it may also be off-center. Fruit bodies of L. indigo have no distinguishable odor.
Lactarius indigo var. diminutivus (the "smaller indigo milk cap") is a smaller variant of the mushroom, with a cap diameter between 3 –, and a stem that is 1.5 – long and 0.3 – thick. It is often seen in Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
. Hesler and Smith, who first described the variant based on specimens found in Brazoria County, Texas
Brazoria County, Texas
Brazoria County[p] is a county in the U.S. state of Texas, located on the Gulf Coast within the Houston–Sugar Land–Baytown metropolitan area. Regionally, parts of the county are within the extreme southern-most fringe of the regions locally known as Southeast Texas. Brazoria County is among a...
, described its typical habitat as "along [the] sides of a muddy ditch under grasses and weeds, [with] loblolly pine
Loblolly Pine
Pinus taeda is one of several pines native to the Southeastern United States, from central Texas east to Florida, and north to Delaware. It is particularly dominant in the eastern half of North Carolina, where there are huge expanses consisting solely of Loblolly Pine trees...
nearby".
Microscopic features
When viewed in mass, as in 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...
, the spores
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...
appear cream to yellow colored. Viewed with a light microscope, the spores are translucent (hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
), elliptical to nearly spherical in shape, with amyloid
Amyloid (mycology)
In mycology the term amyloid refers to a crude chemical test using iodine in either Melzer's reagent or Lugol's solution, to produce a black to blue-black positive reaction. It is called amyloid because starch gives a similar reaction, and that reaction for starch is also called an amyloid reaction...
warts, and have dimensions of 7–9 by 5.5–7.5 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...
. Scanning electron microscopy reveals reticulations on the spore surface. The 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...
is the spore-producing tissue layer of the fruit body, and consists 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 extend into the gills and terminate as end cells. Various cell types can be observed in the hymenium, and the cells have microscopic characteristics that may be used to help identify or distinguish species in cases where the macroscopic characters may be ambiguous. The spore-bearing cells, the basidia, are 4-spored and measure 37–45 µm long by 8–10 µm wide at the thickest point. Cystidia are terminal cells of hyphae in the hymenium which do not produce spores, and function in aiding spore dispersal, and maintaining favorable humidity around developing spores. The pleurocystidia are cystidia that are found on the face of a gill; they are 40–56 by 6.4–8 µm, roughly spindle-shaped, and have a constricted apex. The cheilocystidia—located on the edge of a gill—are abundant, and are 40–45.6 by 5.6–7.2 µm.
Similar species
The characteristic blue color of the fruiting body and the latex make this species easily recognizable. Other Lactarius species with some blue color include the "silver-blue milky" (L. paradoxusLactarius paradoxus
Lactarius paradoxus is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described in 1940....
), found in eastern North America, which has a grayish-blue cap when young, but it has reddish-brown to purple-brown latex and gills. L. chelidonium
Lactarius chelidonium
Lactarius chelidonium is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described by American mycologist Charles Horton Peck in 1870....
has a yellowish to dingy yellow-brown to bluish-gray cap and yellowish to brown latex. L. quieticolor
Lactarius quieticolor
Lactarius quieticolor is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described scientifically by French mycologist Henri Romagnesi in 1958....
has blue-colored flesh in the cap and orange to red-orange flesh in the base of the stem. Although the blue discoloration of L. indigo is thought to be rare in the genus Lactarius, in 2007 five new species were reported from Peninsular Malaysia
Peninsular Malaysia
Peninsular Malaysia , also known as West Malaysia , is the part of Malaysia which lies on the Malay Peninsula. Its area is . It shares a land border with Thailand in the north. To the south is the island of Singapore. Across the Strait of Malacca to the west lies the island of Sumatra...
with bluing latex or flesh, including L. cyanescens
Lactarius cyanescens
Lactarius cyanescens is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described as new to science in 2007....
, L. lazulinus
Lactarius lazulinus
Lactarius lazulinus is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described scientifically in 2007....
, L. mirabilis
Lactarius mirabilis
Lactarius mirabilis is a member of the large milk-cap genus Lactarius in the order Russulales. It was first described in 2007....
, and two species still unnamed.
Edibility
Although Lactarius indigo is a well-known edible species, opinions vary on its desirability. For example, American mycologist David AroraDavid Arora
David Arora is an American mycologist, naturalist, and writer. He is the author of two popular books on mushroom identification, Mushrooms Demystified and All That the Rain Promises and More.......
considers it a "superior edible", while a field guide
Field guide
A field guide is a book designed to help the reader identify wildlife or other objects of natural occurrence . It is generally designed to be brought into the 'field' or local area where such objects exist to help distinguish between similar objects...
on Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...
fungi rates it as "mediocre in quality". It may have a slightly bitter, or peppery taste, and has a coarse, grainy texture. The firm flesh is best prepared by cutting the mushroom in thin slices. The blue color disappears with cooking, and the mushroom becomes grayish. Because of the granular texture of the flesh, it does not lend itself well to drying. Specimens producing copious quantities of milk may be used to add color to marinades.
In Mexico, individuals harvest the wild mushrooms for sale at farmers' markets, typically from June to November, where they are considered a "second class" species for consumption. L. indigo is also sold in Guatemalan markets from May to October. It is one of thirteen Lactarius species sold at rural markets in Yunnan
Yunnan
Yunnan is a province of the People's Republic of China, located in the far southwest of the country spanning approximately and with a population of 45.7 million . The capital of the province is Kunming. The province borders Burma, Laos, and Vietnam.Yunnan is situated in a mountainous area, with...
in southwestern China.
Chemical composition
A chemical analysisAnalytical chemistry
Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials. Qualitative analysis gives an indication of the identity of the chemical species in the sample and quantitative analysis determines the amount of...
of Mexican specimens has shown L. indigo to contain 95.1% moisture
Water content
Water content or moisture content is the quantity of water contained in a material, such as soil , rock, ceramics, fruit, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 to the value of the materials' porosity at...
, 4.3 mg of fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
per gram of mushroom (mg/g), and 13.4 mg/g protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
. There is 18.7 mg/g of dietary fiber
Dietary fiber
Dietary fiber, dietary fibre, or sometimes roughage is the indigestible portion of plant foods having two main components:* soluble fiber that is readily fermented in the colon into gases and physiologically active byproducts, and* insoluble fiber that is metabolically inert, absorbing water as it...
, much higher in comparison to the common button mushroom, which contains 6.6 mg/g. Compared to three other wild edible mushroom species also tested in the study (Amanita rubescens, Boletus frostii
Boletus frostii
Boletus frostii, commonly known as Frost's bolete or the apple bolete, is a bolete mushroom first described scientifically in 1874. A member of the Boletaceae family, the mushrooms produced by the fungus have tubes and pores instead of gills on the underside of its cap...
, and Ramaria flava
Ramaria flava
Ramaria flava , also known by its local name Changle, is a yellow edible coral mushroom native to temperate areas of southern Chile....
), L. indigo contained the highest saturated fatty acids content, including stearic acid
Stearic acid
Stearic acid is the saturated fatty acid with an 18 carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid, and its chemical formula is CH316CO2H. Its name comes from the Greek word στέαρ "stéatos", which means tallow. The salts and esters of stearic acid are called stearates...
with 32.1 mg/g—slightly over half of the total free fatty acid content.
The blue color of Lactarius indigo is due to (7-isopropenyl-4-methylazulen-1-yl)methyl stearate, an organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
known as an azulene
Azulene
Azulene is an organic compound and an isomer of naphthalene. Whereas naphthalene is colourless, azulene is dark blue. Its name is derived from the Spanish word azul, meaning "blue"...
. It is unique to this species, but similar to a compound found in L. deliciosus
Lactarius deliciosus
Lactarius deliciosus, commonly known as the Saffron milk cap, Red pine mushroom, is one of the best known members of the large milk-cap genus Lactarius in the order Russulales...
.
Distribution, habitat, and ecology
Lactarius indigo is distributedRange (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
throughout southern and eastern North America, but is most common along the Gulf Coast and in Mexico. Its frequency of appearance in the Appalachian Mountains
Appalachian Mountains
The Appalachian Mountains #Whether the stressed vowel is or ,#Whether the "ch" is pronounced as a fricative or an affricate , and#Whether the final vowel is the monophthong or the diphthong .), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians...
of the United States has been described as "occasional to locally common". Mycologist David Arora
David Arora
David Arora is an American mycologist, naturalist, and writer. He is the author of two popular books on mushroom identification, Mushrooms Demystified and All That the Rain Promises and More.......
notes that in the United States, the species is found with ponderosa pine
Ponderosa Pine
Pinus ponderosa, commonly known as the Ponderosa Pine, Bull Pine, Blackjack Pine, or Western Yellow Pine, is a widespread and variable pine native to western North America. It was first described by David Douglas in 1826, from eastern Washington near present-day Spokane...
in Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, but is absent in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
's ponderosa pine forests. It has also been collected from China, India, Guatemala, and Costa Rica (in forests dominated by oak). In Europe, it has so far only been found in southern France. A study on the seasonal appearance of fruiting bodies in the subtropical forests of Xalapa
Xalapa
Xalapa-Enríquez, commonly Xalapa or Jalapa, is the capital city of the Mexican state of Veracruz and the name of the surrounding municipality. In the year 2005 census the city reported a population of 387,879 and the municipality of which it serves as municipal seat reported a population of...
, Mexico, confirmed that maximal production coincided with the rainy season
Wet season
The the wet season, or rainy season, is the time of year, covering one or more months, when most of the average annual rainfall in a region occurs. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the...
between June and September.
Lactarius indigo is a mycorrhizal
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
fungus, and as such, establishes a mutualistic relationship with the roots of certain trees ("hosts"), in which the fungi exchange minerals
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
and amino acids extracted from the soil for fixed carbon
Carbon fixation
In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...
from the host. The subterranean hyphae of the fungus grow a sheath of tissue around the rootlets of a broad range of tree species, forming so-called ectomycorrhizae—an intimate association that is especially beneficial to the host, as the fungus produces enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s that mineralize
Mineralization (biology)
In biology, mineralization refers to the process where an organic substance is converted to an inorganic substance.This may also be a normal biological process which takes place during the life of an organism such as the formation of bone tissue or egg shells, largely with calcium.This term may...
organic compounds and facilitate the transfer of nutrients to the tree.
Reflecting their close relationships with trees, the fruit bodies of Lactarius indigo are typically found growing on the ground, scattered or in groups, in both deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
and coniferous forests. They are also commonly found in floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
areas that have been recently submerged. In Mexico, associations have been noted with Mexican alder, American Hornbeam, American Hophornbeam
Ostrya virginiana
Ostrya virginiana , is a species of Ostrya native to eastern North America, from Nova Scotia west to southern Manitoba and eastern Wyoming, southeast to northern Florida and southwest to eastern Texas and northeastern Mexico...
, and Liquidambar macrophylla, while in Guatemala the mushroom associates with Smooth-bark Mexican Pine
Pinus pseudostrobus
Smooth-bark Mexican Pine , distinctive names in Spanish, tree endemic to Mexico.It is 8 to 25 m tall, dense and round top, the bark is brown and fissured and smooth when young. It grows between 1300-3250 m. From 26° to 15° north latitude, from Sinaloa, Mexico to Honduras. It occurs within a...
and other pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
and 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...
species. In Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
, the species forms associations with several native oaks of the Quercus genus. Under controlled laboratory conditions, L. indigo was shown to be able to form ectomycorrhizal associations with the neotropical pine species Mexican White Pine, Hartweg's Pine, Mexican yellow pine
Pinus oocarpa
Pinus oocarpa is a species of pine tree native to Mexico and Central America. It is the national tree of Honduras, where it is known as Ocote. Common names include Pino Amarillo, Pino Avellano, Mexican Yellow Pine, and Hazelnut Pine...
, Smooth-bark Mexican Pine
Pinus pseudostrobus
Smooth-bark Mexican Pine , distinctive names in Spanish, tree endemic to Mexico.It is 8 to 25 m tall, dense and round top, the bark is brown and fissured and smooth when young. It grows between 1300-3250 m. From 26° to 15° north latitude, from Sinaloa, Mexico to Honduras. It occurs within a...
, and also with the Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
n pines Aleppo Pine, European Black Pine, Maritime Pine
Maritime Pine
Pinus pinaster, the Maritime Pine, is a pine native to the western and southwestern Mediterranean region. The pejorative name 'pinaster' is derived from pinus + aster, translating as 'a poor imitation of a pine' Pinus pinaster, the Maritime Pine, is a pine native to the western and southwestern...
and Scots Pine
Scots Pine
Pinus sylvestris, commonly known as the Scots Pine, is a species of pine native to Europe and Asia, ranging from Scotland, Ireland and Portugal in the west, east to eastern Siberia, south to the Caucasus Mountains, and as far north as well inside the Arctic Circle in Scandinavia...
.
External links
- YouTube Video:Hongos del Parque "El Haya" - Lactarius indigo by Armando López and Juventino García, Instituto de Genética Forestal Universidad VeracruzanaUniversidad VeracruzanaUniversidad Veracruzana a public autonomous university located in the Mexican state of Veracruz. Established in 1944, the university is one of the most important in the south-east region of México and has a good projection in all México...