Chemical test in mushroom identification

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Chemical tests in mushroom identification are methods that aid in determining the variety of some fungi. The most useful tests are Melzer's reagent and potassium hydroxide.

Contents

Ammonia

Household ammonia can be used. A couple of drops are placed on the flesh. For example, Boletus spadiceus gives a fleeting blue to blue-green reaction.

Iron salts

Iron salts are used commonly in Russula and Bolete identification. It is best to dissolve the salts in water (typically a 10% solution) and then apply to the flesh, but it is sometimes possible to apply the dry salts directly to see a color change. For example, the white flesh of Boletus chrysenteron stains lemon-yellow or olive. Three results are expected with the iron salts tests: no change indicates a negative reaction; a color change to olive, green or blackish green; or a color change to reddish-pink. [1]

Meixner test for amatoxins

The Meixner test (also known as the Wieland test) uses concentrated hydrochloric acid and newspaper to test for the deadly amatoxins found in some species of Amanita , Lepiota , and Galerina . The test yields false positives for some compounds, such as psilocin. [2]

Melzer's reagent

Melzer's reagent can be used to test whether spores are amyloid, nonamyloid, or dextrinoid.

This test is normally performed on white spored mushrooms. If the spores are not light colored, a change will not be readily apparent. It is easiest to see the color change under a microscope, but it is possible to see it with the naked eye with a good spore print.

Paradimethylaminobenzaldehyde

In the genus Lyophyllum the lamellae usually turn blue with the application of para-Dimethylaminobenzaldehyde (PDAB or pDAB).

Phenol

A 2–3% aqueous solution of phenol gives a color change in some species when applied to the cap or stem.

Potassium hydroxide

A 3–10% solution of potassium hydroxide (KOH) gives a color change in some species of mushrooms:

Schaeffer reaction

Developed by Julius Schäffer to help with the identification of Agaricus species. A positive reaction of Schaeffer's test, which uses the reaction of aniline and nitric acid on the surface of the mushroom, is indicated by an orange to red color; it is characteristic of species in the section Flavescentes. The compounds responsible for the reaction were named schaefferal A and B to honor Schäffer. [3]

Two intersecting lines are drawn on the surface of the cap, the first with aniline or aniline water, the second with an aqueous solution of 65% nitric acid. The test is considered positive when a bright orange color forms where the lines cross. [4] [5] [6]

Agaricus placomyces and Agaricus xanthodermus produce false negative reactions. [4] [5]

Sometimes referred to as "Schaeffer's reaction", "Schaeffer's cross reaction" or "Schaeffer's test".

Aniline + acid(s)

Kerrigan's 2016 Agaricus of North America P45: (Referring to Schaffer's reaction) "In fact I recommend switching to the following modified test. Frank (1988) developed an alternative formulation in which aniline oil is combined with glacial acetic acid (GAA, essentially distilled vinegar) in a 50:50 solution. GAA is a much safer, less reactive acid. This single combined reagent is relatively stable over time. A single spot or line applied to the pileus (or other surface). In my experience the newer formulation works as well as Schaffer's while being safer and more convenient." [7]

Sulfo-vanillin

Made from sulfuric acid (H2SO4) and vanillin (vanilla). Used in Russula and Panaeolus identification.

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<i>Agaricus bisporus</i> Species of fungus

Agaricus bisporus, commonly known as the cultivated mushroom, is a basidiomycete mushroom native to grasslands in Eurasia and North America. It has two color states while immature – white and brown – both of which have various names, with additional names for the mature state, including portobello.

<span class="mw-page-title-main">Melzer's reagent</span> Stain for fungus parts to identify them

Melzer's reagent is a chemical reagent used by mycologists to assist with the identification of fungi, and by phytopathologists for fungi that are plant pathogens.

<i>Russula emetica</i> Species of fungus in the family Russulaceae with a wide distribution in the Northern Hemisphere

Russula emetica, commonly known as the sickener, emetic russula, or vomiting russula, is a basidiomycete mushroom, and the type species of the genus Russula. It has a red, convex to flat cap up to 8.5 cm (3.3 in) in diameter, with a cuticle that can be peeled off almost to the centre. The gills are white to pale cream, and closely spaced. A smooth white stem measures up to 10.5 cm (4.1 in) long and 2.4 cm (0.9 in) thick. First described in 1774, the mushroom has a wide distribution in the Northern Hemisphere, where it grows on the ground in damp woodlands in a mycorrhizal association with conifers, especially pine.

<i>Russula xerampelina</i> Species of fungus

Russula xerampelina, also commonly known as the shrimp russula, crab brittlegill, or shrimp mushroom, is a basidiomycete mushroom of the brittlegill genus Russula. Two subspecies are recognised. The fruiting bodies appear in coniferous woodlands in autumn in northern Europe and North America. Their caps are coloured various shades of wine-red, purple to green. Mild tasting and edible, it is one of the most highly regarded brittlegills for the table. It is also notable for smelling of shellfish or crab when fresh.

<i>Caloboletus calopus</i> Species of fungus in the family Boletaceae found in Asia, Northern Europe and North America

Caloboletus calopus, commonly known as the bitter beech bolete or scarlet-stemmed bolete, is a fungus of the bolete family, found in Asia, Northern Europe and North America. Appearing in coniferous and deciduous woodland in summer and autumn, the stout fruit bodies are attractively coloured, with a beige to olive cap up to 15 cm (6 in) across, yellow pores, and a reddish stipe up to 15 cm (6 in) long and 5 cm (2 in) wide. The pale yellow flesh stains blue when broken or bruised.

<i>Tylopilus felleus</i> Species of fungus

Tylopilus felleus, commonly known as the bitter bolete or the bitter tylopilus, is a fungus of the bolete family. Its distribution includes east Asia, Europe and eastern North America, extending south into Mexico and Central America. A mycorrhizal species, it grows in deciduous and coniferous woodland, often fruiting under beech and oak. Its fruit bodies have convex to flat caps that are some shade of brown, buff or tan and typically measure up to 15 cm (6 in) in diameter. The pore surface is initially white before turning pinkish with age. Like most boletes it lacks a ring and it may be distinguished from Boletus edulis and other similar species by its unusual pink pores and the prominent dark-brown net-like pattern on its stalk.

In mycology a tissue or feature is said to be amyloid if it has a positive amyloid reaction when subjected to a crude chemical test using iodine as an ingredient of either Melzer's reagent or Lugol's solution, producing a blue to blue-black staining. The term "amyloid" is derived from the Latin amyloideus ("starch-like"). It refers to the fact that starch gives a similar reaction, also called an amyloid reaction. The test can be on microscopic features, such as spore walls or hyphal walls, or the apical apparatus or entire ascus wall of an ascus, or be a macroscopic reaction on tissue where a drop of the reagent is applied. Negative reactions, called inamyloid or nonamyloid, are for structures that remain pale yellow-brown or clear. A reaction producing a deep reddish to reddish-brown staining is either termed a dextrinoid reaction or a hemiamyloid reaction.

<i>Suillus variegatus</i> Species of fungus

Suillus variegatus, commonly called the velvet bolete or variegated bolete, is a species of edible mushroom in the genus Suillus. Like all bolete-like species it has tubes, and pores, instead of gills under its cap. The mushroom forms a mycorrhizal relationship with pine and occurs in North America and Eurasia.

<i>Russula heterophylla</i> Species of fungus

The edible wild mushroom Russula heterophylla, that has lately been given the common name of the greasy green brittlegill is placed in the genus Russula, the members of which are mostly known as brittlegills. It is a variably colored mushroom, found in deciduous forests, and woods in Britain, Europe, and Scandinavia. Appearing with broad-leaved trees in summer to early autumn, it usually has a greenish coloration.

<i>Butyriboletus appendiculatus</i> Species of fungus

Butyriboletus appendiculatus is an edible pored mushroom that grows under oaks and other broad leaved trees such as beech. It is commonly known as the butter bolete. It often grows in large colonies beneath the oak trees, and is frequently found cohabiting with old oaks in ancient woodland. It is relatively rare in Britain. Its stipe and pores are often bright yellow and its flesh stains bright blue when cut or bruised.

<i>Aureoboletus mirabilis</i> Species of fungus

Aureoboletus mirabilis, commonly known as the admirable bolete, the bragger's bolete, and the velvet top, is an edible species of fungus in the Boletaceae mushroom family. The fruit body has several characteristics with which it may be identified: a dark reddish-brown cap; yellow to greenish-yellow pores on the undersurface of the cap; and a reddish-brown stem with long narrow reticulations. Aureoboletus mirabilis is found in coniferous forests along the Pacific Coast of North America, and in Asia. Unusual for boletes, A. mirabilis sometimes appears to fruit on the wood or woody debris of Hemlock, suggesting a saprobic lifestyle. Despite occasional appearances to the contrary, Aureoboletus mirabilis is mycorrhizal, and forms close mutualistic associations with hemlock roots.

<i>Leccinum manzanitae</i> Species of fungus

Leccinum manzanitae is an edible species of bolete fungus in the family Boletaceae. Described as new to science in 1971, it is commonly known as the manzanita bolete for its usual mycorrhizal association with manzanita trees. Its fruit bodies (mushrooms) have sticky reddish to brown caps up to 20 cm (8 in), and its stipes are up to 16 cm (6.3 in) long and 3.5 cm (1.4 in) thick. They have a whitish background color punctuated with small black scales known as scabers. Found only in the Pacific Northwest region of the United States and Canada, it is the most common Leccinum species in California. The mushroom is edible, although opinions vary as to its quality. L. manzanitae can be usually distinguished from other similar bolete mushrooms by its large size, reddish cap, dark scabers on a whitish stipe, and association with manzanita and madrone.

<i>Suillellus amygdalinus</i> Species of fungus

Suillellus amygdalinus is a fungus of the bolete family found in western North America. The fruit bodies, or mushrooms, are characterized by their thick, red to brown caps, red pores, and the strong bluing reaction observed when the mushroom tissue is injured or cut. The cap can reach diameters of up to 12 cm (4.7 in) and the stipe 9 cm (3.5 in) long by 3 cm (1.2 in) thick at maturity. This mushroom has been found in manzanita and madrone woodlands of central California north to southern Oregon. Although the edibility of the mushroom is not known with certainty, it may be poisonous, and is not recommended for consumption. Other similar red-pored, bluing boletes from North America, including Rubroboletus eastwoodiae, Boletus luridiformis, and B. subvelutipes, can be distinguished from S. amygdalinus either by the color of the cap, the degree of reticulation on the stipe, or by location.

<i>Agaricus deserticola</i> Species of fungus in the family Agaricaceae endemic to southwestern and western North America

Agaricus deserticola, commonly known as the gasteroid agaricus, is a species of fungus in the family Agaricaceae. Found only in southwestern and western North America, A. deserticola is adapted for growth in dry or semi-arid habitats. The fruit bodies are secotioid, meaning the spores are not forcibly discharged, and the cap does not fully expand. Unlike other Agaricus species, A. deserticola does not develop true gills, but rather a convoluted and networked system of spore-producing tissue called a gleba. When the partial veil breaks or pulls away from the stem or the cap splits radially, the blackish-brown gleba is exposed, which allows the spores to be dispersed.

<i>Gyroporus cyanescens</i> Species of fungus

Gyroporus cyanescens, commonly known as the bluing bolete or the cornflower bolete, is a species of bolete fungus in the family Gyroporaceae. First described from France in 1788, the species is found in Asia, Australia, Europe, and eastern North America, where it grows on the ground in coniferous and mixed forests.

Julius Schäffer was a German mycologist. His contributions include studies on the Agaricales, especially the genus Russula, about which he wrote a monograph in 1933. Later, he revised the genus in the series Die Pilze Mitteleuropas (1926–1967); his notes were published posthumously by his wife Liesel in 1952 with the help of other mycologists. The work was considered the "authoritative treatment of the group for Central Europe". One of the Russula species that was first described in this publication was R. laeta. Schäffer developed a chemical test to help with the identification of Agaricus species. A positive reaction of Schaeffer's test, which uses the reaction of aniline and nitric acid on the surface of the mushroom, is indicated by an orange to red color; it is characteristic of species in the section Flavescentes. The compounds responsible for the reaction were named schaefferal A and B to honor Schäffer.

<i>Boletus rubroflammeus</i> Species of fungus

Boletus rubroflammeus is a species of bolete fungus in the family Boletaceae. First described from Michigan in 1971, it is found in the eastern United States and Mexico, where it grows in a mycorrhizal association with hardwood trees. The fruit bodies (mushrooms) of the fungus have caps that are deep red to purplish red, and dark red pores. The stem has coarse, dark red reticulations and a narrow yellow area at the top. All parts of the mushroom quickly stain blue when injured or cut. Lookalikes include Boletus flammans, a lighter-colored species that grows with conifers. Other similar species can be distinguished by differences in distribution, morphology, staining reaction, and microscopic characteristics. Boletus rubroflammeus mushrooms are poisonous, and can cause gastrointestinal distress if consumed.

<i>Boletus abruptibulbus</i> Species of fungus

Boletus abruptibulbus is a species of bolete mushroom in the family Boletaceae. Described as new to science in 2009, it is found only in the Gulf Coast of the Florida Panhandle, where it grows on the ground in coastal sand dunes, one of only three North American boletes known to favor this habitat. The fruit bodies have convex brownish caps up to 8 cm (3.1 in) in diameter, supported by solid yellowish to reddish stems measuring 3–5 cm (1.2–2.0 in) long by 10–15 mm (0.4–0.6 in) thick. The pores on the underside of the cap measure about 1–2 mm in diameter and are initially pale yellow before developing a greenish tinge in age. The mushroom's spores, about 20 micrometers long, are unusually long for a member of the Boletaceae. The stem base is bulbous, a diagnostic feature for which the species is named.

<i>Boletus subluridellus</i> Species of fungus

Boletus subluridellus is a species of bolete fungus in the family Boletaceae. Described as new to science in 1971 by American mycologists, the bolete is found in the eastern United States and Canada. It grows on the ground in coniferous and mixed forests in a mycorrhizal association with deciduous trees, especially oak. The fruit bodies (mushrooms) have orangish-red, broadly convex caps that are up to 10 cm (3.9 in) in diameter, with small, dark reddish pores on the underside. The pale yellow stipe measures 4–9 cm (1.6–3.5 in) long by 1.5–2.3 cm (0.6–0.9 in) thick. All parts of the fruit body will quickly stain blue when injured or touched.

References

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  2. Beuhler, M; Lee, DC; Gerkin, R (2004). "The Meixner test in the detection of alpha-amanitin and false-positive reactions caused by psilocin and 5-substituted tryptamines". Annals of Emergency Medicine. 44 (2): 114–20. doi:10.1016/j.annemergmed.2004.03.017. PMID   15278082.
  3. Kileci-Ksoll R, Winklhoer C, Steglich W (2010). "Synthesis of schaefferals A and B, unusual phenylhydrazine derivatives from mushrooms of the genus Agaricus". Synthesis. 2010 (13): 2287–91. doi:10.1055/s-0029-1218790.
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