What You Should Know
Rubroboletus dupainii is a bolete fungus of the genus Rubroboletus. It is characterized by its sticky, bright red cap; its blue-bruising, red pore surface; and its yellow stem, which is covered with tiny flecks of red. Although the cap dries out quickly, its former stickiness is usually still in evidence in the form of adhering leaves and debris and a glossy sheen.
It is rare, but widespread in central-southern Europe and the Russian Caucasus, and Turkey. The species is reported to be in decline in some countries and is included in Red Lists in most countries of occurrence.
It also occurs in North America, although it is rare there. It was first recorded from North Carolina, and then from Iowa in 2009. It was reported from Belize in 2007, growing under Quercus peduncularis and other oaks.
Other names: Dupain's Bolete, Hríb Dupainov (Slovenia), Bolet de Dupain (France), Blutroter Purpurröhrling (Austria).
Rubroboletus dupainii Mushroom Identification
Mycorrhizal with oaks; growing alone, scattered, or gregariously; early summer through fall; possibly widely distributed east of the Great Plains.
4.5–10 cm across; convex, becoming broadly convex or nearly flat; sticky when fresh; bald; shiny when dry, and often covered with adhering leaves or debris; deep, bright red, fading somewhat with age; when very young with a dull pinkish bloom overall (later the bloom can sometimes be seen on the margin); when fresh bruising dark blue; staining waxed paper yellow.
Initially deep red to bright orangish-red, with deep yellow marginal areas; becoming reddish-orange, then orangish brown to olive; bruising promptly dark blue or nearly black; 3-4 round pores per mm; tubes to 1 cm deep.
3–9 cm long; 1–2 cm thick; more or less equal; not reticulate; yellow, decorated with fine red flecks and scales that are more densely packed towards the base; bright yellow at the apex; bruising blue; basal mycelium white, bruising dark purplish red.
Pale yellow in the cap; deep bright yellow to red in the stem; bluing when sliced.
Odor and Taste
Odor is not distinctive; tastes slightly acidic, or not distinctive.
Ammonia negative to orangish or yellow on cap surface; negative (but erasing blue) to yellow or orangish on flesh. KOH negative to orange or dull, pale olive on cap surface; negative to orangish on flesh. Iron salts are negative to grayish or dark gray on cap surface; negative to gray on flesh.
Caps retain the bright red shade for several years, but after about 10 years become dull brownish-red.
Spores 10–13 x 3–5 µm; smooth; subfusiform; yellow in KOH. Hymenial cystidia inconspicuous; hyaline in KOH; fusoid-ventricose to fusiform; to about 35 µ long. Pileipellis is a cutis of hyphae 2–4 µm wide; golden yellow in KOH (but after about 10 years of preservation merely yellowish or nearly hyaline); terminal elements cylindric with rounded apices.
Rubroboletus dupainii Look-Alikes
Imperator torosus, Rubroboletus legaliae, Boletus luteocupreus, Boletus splendidus, Rubroboletus eastwoodiae, Boletus satanoides, Rubroboletus purpureus, Rubroboletus rhodoxanthus, Rubroboletus rubrosanguineus, Rubroboletus satanas.
Boletus calopus, Boletus permagnificus.
Boletus erythropus, Boletus luridus, Boletus pulverulentus.
Rubroboletus dupainii Taxonomy
The binomial name was determined by the French mycologist Émile Boudier in volume 18 of the mycological journal Bulletin de la Société Mycologique de France from 1902, which was the current name until 2015, and is listed under this taxon in most current books.
In 2014 Chinese mycologists K. Zhao & Z.L.Yang described the new genus Rubroboletus. This taxon is the current valid name (2020).
René Maire's name Tubiporus dupainii from 1937 as well as that of Jaime Blanco-Dios from 2015, namely Suillellus dupainii, are accepted synonymously.
The epithet was created by Emile Boudier in honor of his compatriot Victor Augustin Dupain (1857-1940), a pharmacist and mycologist.
Rubroboletus dupainii Synonyms
Boletus dupainii Boud. (1902)
Tubiporus dupainii (Boud.) Maire (1937)
Suillellus dupainii (Boud.) Blanco-Dios
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