Chemical tests in mushroom identification are methods that aid in determining the variety of some fungi. The most useful tests are
Melzer's reagent
Melzer's reagent (also known as Melzer's iodine reagent, Melzer's solution or informally as Melzer's) is a chemical reagent used by mycologists to assist with the identification of fungi, and by phytopathologists for fungi that are plant pathogens ...
and
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
.
Ammonia
Household
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
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
''Russula'' is a very large genus composed of around 750 worldwide species of ectomycorrhizal mushrooms. They are typically common, fairly large, and brightly colored – making them one of the most recognizable genera among mycologists and mushr ...
'' and
Bolete
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A bolete is a type of mushroom, or fungal fruiting body. It can be identified thanks to a unique mushroom cap. The cap is clearly different from the stem. On the underside of the cap there is usually a spongy surf ...
identification. It is best to dissolve the salts in water (typically a 10% solution) and then apply to the
flesh
Flesh is any aggregation of soft tissues of an organism. Various multicellular organisms have soft tissues that may be called "flesh". In mammals, including humans, ''flesh'' encompasses muscles, fats and other loose connective tissues, but ...
, but it is sometimes possible to apply the dry salts directly to see a color change. For example, the white flesh of ''
Boletus chrysenteron
''Xerocomellus chrysenteron'', formerly known as ''Boletus chrysenteron'' or ''Xerocomus chrysenteron'', is a small, edible, wild mushroom in the family Boletaceae. These mushrooms have tubes and pores instead of gills beneath their caps. It i ...
'' 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.
Meixner test for amatoxins
The Meixner test (also known as the Wieland test) uses concentrated
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
and newspaper to test for the deadly
amatoxin Amatoxin is the collective name of a subgroup of at least nine related toxic compounds found in three genera of poisonous mushrooms (''Amanita'', '' Galerina'' and '' Lepiota'') and one species ( Conocybe filaris) of the genus '' Conocybe''. Amatoxi ...
s found in some species of ''
Amanita
The genus ''Amanita'' contains about 600 species of agarics, including some of the most toxic known mushrooms found worldwide, as well as some well-regarded edible species. This genus is responsible for approximately 95% of the fatalities resul ...
'', ''
Lepiota
''Lepiota'' is a genus of gilled mushrooms in the family Agaricaceae. All ''Lepiota'' species are ground-dwelling saprotrophs with a preference for rich, calcareous soils. Basidiocarps (fruit bodies) are agaricoid with whitish spores, typically ...
'', and ''
Galerina
''Galerina'' is a genus of small brown-spore saprobic fungi (colloquially often ''mushrooms''), with over 300 species found throughout the world from the far north to remote Macquarie Island in the Southern Ocean. The genus is most noted for some ...
''. The test yields false positives for some compounds, such as
psilocin
Psilocin (also known as 4-HO-DMT, 4-hydroxy DMT, psilocine, psilocyn, or psilotsin) is a substituted tryptamine alkaloid and a serotonergic psychedelic substance. It is present in most psychedelic mushrooms together with its phosphorylated cou ...
.
Melzer's reagent
Melzer's reagent
Melzer's reagent (also known as Melzer's iodine reagent, Melzer's solution or informally as Melzer's) is a chemical reagent used by mycologists to assist with the identification of fungi, and by phytopathologists for fungi that are plant pathogens ...
can be used to test whether spores are
amyloid
Amyloids are aggregates of proteins characterised by a fibrillar morphology of 7–13 nm in diameter, a beta sheet (β-sheet) secondary structure (known as cross-β) and ability to be stained by particular dyes, such as Congo red. In the huma ...
,
nonamyloid, or
dextrinoid
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 staini ...
.
* Spores that stain bluish-gray to bluish-black are amyloid
* Spores that stain brown to reddish-brown are 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
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
''
Lyophyllum
''Lyophyllum'' is a genus of about 40 species of fungi, widespread in north temperate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the ...
'' the
lamellae
Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to:
Biology
* Lamella (mycology), a papery rib beneath a mushroom cap
* Lamella (botany)
* Lamella (surface anatomy), a plate-like structure in an animal
* ...
usually turn blue with the application of
para-Dimethylaminobenzaldehyde (PDAB or pDAB).
Phenol
A 2–3% aqueous solution of
phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...
gives a color change in some species when applied to the cap or stem.
Potassium hydroxide
A 3–10% solution of
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
(KOH) gives a color change in some species of mushrooms:
* In ''
Agaricus
''Agaricus'' is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom ('' Agaricus bi ...
'', some species such as ''
A. xanthodermus'' turn yellow with KOH, many have no reaction, and ''
A. subrutilescens'' turns green.
* Distinctive change occurs for some species of ''
Cortinarius
''Cortinarius'' is a globally distributed genus of mushrooms in the family Cortinariaceae. It is suspected to be the largest genus of agarics, containing over 2,000 widespread species. A common feature among all species in the genus ''Cortinari ...
'' and
Boletes
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A bolete is a type of mushroom, or fungal fruiting body. It can be identified thanks to a unique mushroom cap. The cap is clearly different from the stem. On the underside of the cap there is usually a spongy surfa ...
Schaeffer reaction
Developed by
Julius Schäffer Julius Schäffer (3 June 1882 – 21 October 1944) was a German mycologist. His contributions include studies on the Agaricales
The fungal order Agaricales, also known as gilled mushrooms (for their distinctive gills) or euagarics, contains some ...
to help with the identification of ''
Agaricus
''Agaricus'' is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom ('' Agaricus bi ...
'' species. A positive reaction of Schaeffer's test, which uses the reaction of
aniline
Aniline is an organic compound with the formula C6 H5 NH2. Consisting of a phenyl group attached to an amino group, aniline is the simplest aromatic amine. It is an industrially significant commodity chemical, as well as a versatile starti ...
and
nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
on the surface of the mushroom, is indicated by an orange to red color; it is characteristic of species in the
section
Section, Sectioning or Sectioned may refer to:
Arts, entertainment and media
* Section (music), a complete, but not independent, musical idea
* Section (typography), a subdivision, especially of a chapter, in books and documents
** Section sig ...
''Flavescentes''. The compounds responsible for the reaction were named schaefferal A and B to honor Schäffer.
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.
''
Agaricus placomyces'' and ''
Agaricus xanthodermus
''Agaricus xanthodermus'', commonly known as the yellow-staining mushroom or simply the yellow-stainer, is a mushroom of the
genus ''Agaricus'', which displays a strong yellow colouration at the base of the stem when cut. It is poisonous for mos ...
'' produce false negative reactions.
Sometimes referred to as "Schaeffer's reaction", "Schaeffer's cross reaction" or "Schaeffer's test".
Sulfo-vanillin
Made from
sulfuric acid (H
2SO
4) and
vanillin
Vanillin is an organic compound with the molecular formula . It is a phenolic aldehyde. Its functional groups include aldehyde, hydroxyl, and ether. It is the primary component of the extract of the vanilla bean. Synthetic vanillin is now u ...
(vanilla). Used in ''
Russula
''Russula'' is a very large genus composed of around 750 worldwide species of ectomycorrhizal mushrooms. They are typically common, fairly large, and brightly colored – making them one of the most recognizable genera among mycologists and mushr ...
'' and ''
Panaeolus
''Panaeolus'' is a genus of small, black-spored, saprotrophic agarics. The word ''Panaeolus'' is Greek for "all variegated", alluding to the spotted gills of the mushrooms produced.
Characteristics
These fungi are mostly dung and grassland sp ...
'' identification.
References
{{reflist
* Arora, David "Mushrooms Demystified" 2nd Edition, Ten Speed Press, Berkeley, 1986
* Jordan, Michael "The Encyclopedia of Fungi of Britain and Europe" Frances Lincoln 2004
* Kuo, Michael "100 Edible Mushrooms", University of Michigan Press, Ann Arbor 2007
* Largent, David L., Baroni, Timothy J. "How to Identify Mushrooms to Genus VI: Modern Genera" Mad River Press 1988
External links
MushroomExpert.com
Mycology
Mushroom identification