What You Should Know
Suillus americanus is a species of fungus in the mushroom family Suillaceae. It grows in a mycorrhizal association with eastern white pine and is found where this tree occurs in eastern North America and China. The mushroom can be recognized by the bright yellow cap with red to reddish-brown scales embedded in slime, the large yellow angular pores on the underside of the cap, and the narrow yellow stem marked with dark reddish dots.
It is edible, although opinions vary as to its palatability; some susceptible individuals may suffer contact dermatitis after touching the fruit bodies. The fruit bodies contain a beta-glucan carbohydrate shown in laboratory tests to have anti-inflammatory properties.
Other names: American Slippery Cap, American Slippery Jack, Chicken-Fat Suillus, Eastern Pine Bolete.
Suillus americanus Mushroom Identification
Mycorrhizal with eastern white pine; typically growing gregariously; summer and fall; widely distributed east of the Rocky Mountains (reported from the Southwest but possibly confused with Suillus sibiricus-assuming the two species are indeed distinct).
3-10 cm; convex with an inrolled margin when young, but soon broadly convex to wavy to, well, rather shapeless; white to yellow-brown veil tissue hanging from the margin; slimy; bright yellow, sometimes dingy yellow; frequently with reddish-brown patches and markings.
Yellow, darker with age; bruising reddish-brown; pores angular and vaguely radially arranged (but not boletinoid), 1-2 mm across; tubes 7-10 mm deep.
3-10 cm long; up to about 1 cm thick; frequently crooked or bent; with reddish-brown glandular dots; occasionally with a ring or ring zone, but usually bare; frequently bruising reddish brown.
Yellow throughout, staining purplish brown.
Odor and Taste
Ammonia on cap surface with a pink flash, then red, then black; on flesh brown or black. KOH on cap surface black; on flesh dark brown. Iron salts on flesh olive.
Cinnamon to brown.
Spores 8-12 x 3-4 µ; smooth; fusoid.
Suillus americanus Look-Alikes
Is distributed in western North America and western and central Asia but the latter species is associates with Pinus monticola and Pinus flexilis rather than Pinus strobus. One field guide suggests that Suillus sibiricus has a thicker stem than S. americanus, brown spots on the cap, and is a darker, more dingy yellow. Molecular phylogenetics analysis has shown, however, that specimens of S. sibricus collected from China and western North America, as well as S. americanus from eastern North America, are most likely "a single circumboreal taxon".
Distinguished microscopically by slightly smaller, hyaline (translucent) spores (typically 7.5–8.5 by 3 µm), and an association with Quaking Aspen (Populus tremuloides).
Suillus americanus Allergenicity
Some susceptible individuals have experienced an allergic reaction after touching Suillus americanus. The symptoms of allergic contact dermatitis generally develop one to two days after initial contact, persist for roughly a week, then disappear without treatment. Cooking the fruit bodies inactivates the responsible allergens.
Suillus americanus Bioactive Compounds
Suillus americanus contains a polysaccharide known as a beta-glucan that laboratory tests suggest may have anti-inflammatory activity. Known specifically as a (1→3)-, (1→4)-β-D-glucan, its natural function is as a component of the fungal cell wall, where it forms microcrystalline fibrils in the wall that give it rigidity and strength. The anti-inflammatory activity results from the polysaccharide's ability to inhibit the production of nitric oxide in activated macrophages, a cell of the immune system.
Suillus americanus Taxonomy and Etymology
Suillus americanus was first described scientifically by American mycologist Charles Horton Peck in 1888, based on specimens he had originally collected as far back as 1869, in New York state, near Sand Lake, Albany, and Port Jefferson. In his 1888 publication, he indicated that he had originally listed these collections as Boletus flavidus (now known as Suillus flavidus) in his 1869 Report of the State Botanist (published in 1872). However, as was pointed out nearly a century later in 1986, the 1869 report does not mention the species; rather, Peck's field notes that year (which served as the basis for the report) reference a collection at Sand Lake upon which the original (1888) description was most likely based. Because Peck failed to designate a type specimen, one of the Sand Lake specimens was lectotypified in 1986.
In 1931, French mycologist Édouard-Jean Gilbert transferred the species to the genus Ixocomus, a now-defunct taxon that has since been subsumed into Suillus. In 1959, Walter H. Snell, collaborating with Rolf Singer and Esther A. Dick, transferred the species to Suillus. In his 1986 version of the authoritative monograph The Agaricales in Modern Taxonomy, Singer included the species in the subsection Latiporini of genus Suillus, an infrageneric grouping (below the taxonomic level of genus) characterized by a cinnamon-colored spore print without an olive tinge, and wide pores, typically greater than 1 mm when mature.
Common names for the species include the American slippery cap, the American suillus, or the chicken-fat mushroom. The latter name is a reference to its yellow color. The specific epithet americanus means "of America".
Suillus americanus Synonyms
Boletus americanus Peck (1887)
Ixocomus americanus (Peck) E.-J. Gilbert (1931)
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