Suillellus rhodoxanthus (Krombh.) Blanco-Dios 2015

Rubroboletus rhodoxanthus is a species of bolete in the family Boletaceae, native to Europe. Previously known as Boletus rhodoxanthus, it was transferred in 2014 to the newly erected genus Rubroboletus, based on DNA data.

It produces large, colourful fruit bodies with pink patches on the cap, red pores in the hymenial surface and has a robust stem decorated in a dense, red-coloured network pattern. When longitudinally sliced, its flesh is distinctly bright yellow in the stem and discolours blue only in the cap, an excellent diagnostic feature distinguishing it from similar species.

The fungus is more widespread in warm broad-leaved forests of southern Europe, where it grows in mycorrhizal symbiosis with trees of the family Fagaceae, particularly oak (Quercus) and beech (Fagus). However, it is rare in northern regions and regarded as critically endangered or extinct in some countries.

Rubroboletus rhodoxanthus is generally regarded as inedible and may cause adverse gastrointestinal symptoms if consumed.

Taxonomy and phylogeny

The fungus was first described in 1836 by Czech mycologist Julius Vincenz von Krombholz, who considered it to be a variety of Boletus sanguineus.^[1] In 1925, it was recombined as a distinct species by German mycologist Franz Joseph Kallenbach,^[2] and the fungus remained in genus Boletus until 2014. The species epithet is derived from the Ancient Greek words ρόδο (rhódo, "rose" or "pink") and ξανθός (xanthós, "blonde" or "fair").

The first extensive phylogenetic studies on Boletaceae in 2006^[3] and 2013,^[4] indicated that Boletus was not monophyletic and hence an artificial arrangement. A 2014 study by Wu and colleagues recognised 22 generic clades within Boletaceae, concluding that Boletus dupainii and some closely related red-pored species belong to a distinct clade, distant from the core clade of Boletus (comprising Boletus edulis and allied taxa).^[5] The new genus Rubroboletus was therefore described to accommodate species in this clade and B. rhodoxanthus was transferred to this genus.^[6] The placement of the species in genus Suillellus, following an online recombination by Blanco-Dios,^[7] was not supported by molecular data and has been subsequently rejected by later authors.^{[8][9][10][11]}

Description

The cap is at first hemispherical, gradually becoming convex to almost flat as the fungus expands, with a diameter of 10 to 20 cm (4 to 8 in), but can sometimes grow up to 30 cm (12 in). It is at first slightly velvety and coloured mostly whitish-grey, but soon becomes smooth, pinkish-grey, pinkish-beige or pinkish-red, especially towards the margin or when handled.^[12][13][14]

The tubes are adnate to emarginate, 0.5 to 1.5 cm (0 to 0.5 in) long and initially yellow, becoming somewhat olivaceous-yellow in very mature fruit bodies and staining blue when cut. The pores (tube mouths) are orange to deep red and instantly bluing when handled.^[15][16]

The stem is 8 to 12 cm (3 to 4.5 in) long by 3 to 6 cm (1 to 2.5 in) wide, bulbous or clavate when young, becoming more elongated and cylindrical at maturity. It is orange or orange-yellow at the top (apex), gradually becoming orange-red to carmine-red in the lower part and bears a dense, orange-red to carmine-red reticulation (network pattern).^[17][18]

Sectioned fruit body displaying the characteristic yellow flesh and bluing in the cap.

The flesh is distinctly bright yellow and unchanging in the stem, but paler and turning blue when cut only in the cap. It has a mild taste.^[19]

The spores are olive-brown in mass. When viewed under the microscope they are ellipsoid to fusiform (spindle-shaped), measuring 10–15.5 by 4–5.5 μm. The cap cuticle is a trichodermium of septate cylindrical hyphae, sometimes finely incrusted.^[13][20]

Similar species

• Rubroboletus legaliae is very similar, but has a distinctive smell of chicory or hay and whitish flesh that stains blue in the cap, as well as the stem when cut.
• Rubroboletus satanas has a whitish cap without flushes of pink and whitish flesh that usually stains pale blue also in the stem when cut.
• Rubroboletus rubrosanguineus is mycorrhizal with spruce (Picea) or fir (Abies) and has pale yellow flesh that stains blue throughout.
• Rubroboletus demonensis, so far known only from southern Italy (Calabria and Sicily), has usually brighter colours on the cap ranging from pale grey to blood-red or purple, has yellow flesh that stains weakly to moderately blue throughout and microscopically has smaller spores, measuring 12.5–14 × 4.5–5 μm.
• Imperator rhodopurpureus differs by its pinkish-red to crimson-red cap that has a roughened or "hammered" appearance and stains blue when handled, but also by its flesh that stains intensely dark blue throughout.

Distribution and habitat

Regarded as a rare species in northern Europe, Rubroboletus rhodoxanthus is more frequently encountered in warm, southern regions. It forms ectomycorrhizal associations with members of the Fagaceae, particularly oak (Quercus) and beech (Fagus), but sometimes also with chestnut (Castanea).^[20][15] Molecular phylogenetic testing has confirmed its presence in France,^[11] Italy,^[6] Portugal^[21] and the islands of Cyprus^[11] and Sardinia,^[6] but it is probably widespread throughout most of the Mediterranean region.^[17][20]

It has been reported as locally frequent on the island of Cyprus, where it appears in seasons with early rainfall, growing on serpentine soil under the endemic golden oak (Quercus alnifolia).^[22] In contrast, it is considered critically endangered in the Czech Republic^[23] and reported as extinct in England.^[18] In the British Islands it known only from Northern Ireland.^[19]

Toxicity

Rubroboletus rhodoxanthus is generally regarded as inedible^[13] or even poisonous,^[24][18][10] and can cause an adverse gastrointestinal reaction if eaten. In the Colour Atlas of Poisonous Fungi,^[25] Bresinsky and Besl claim that the fungus might be edible if thoroughly cooked, but warn against collecting it because of its rarity and possibility of confusion with R. satanas.

References

Oharra: ez fidatu soilik orri honetan ematen diren datuez perretxiko bat identifikatzeko orduan. Inolako zalantzarik izanez gero, kontsultatu aditu batekin.

1. ↑ Euskal Herriko perretxiko eta onddoak, Fernado Pedro Pérez, 2013, 2014, 2017, Kultura Saila, Eusko Jaurlaritza
   Bizkaiko Perretxiko eta Onddoak, Fernando Pedro Pérez, 2012ko Abendua, A.D.E.V.E, Argazkiak:Fernando Pedro Pérez, Maite Legarra, Xabier Leizaola, Jon Urkijo, Nerea Aurtenetxe.

Il boleto rosseggiante (Boletus rhodoxanthus (Krombh.) Kallenb., 1925) è un fungo basidiomicete della famiglia delle Boletaceae dalla livrea brillante, caratterizzato dal contrasto tra il colore del cappello, bianco con bordo rosa, e l'intenso colore rosso-sangue dei pori.

Etimologia

Dal greco rhódon = rosa e xanthós = giallo, cioè roseo e giallo, per il colore del cappello.

Descrizione della specie

Cappello

6–20 cm, prima emisferico, poi convesso, carnoso.

Cuticola

di colore biancastro, con sfumature rossastre più marcate al margine, alla pressione vira al giallo-bruno, leggermente feltrata, tomentosa, poi liscia.

Tubuli

Corti, giallo-verdi, poi blu-verdi al tocco.

Pori

Piccoli, arrotondati, da giallastri a rosso-arancio a rosso sangue, al tocco virano al blu-verdastro.

Gambo

6-12 x 3–5 cm, cilindrico o leggermente ingrossato alla base, color giallo vivo all'apice, rossastro alla base, ricoperto da un sottile reticolo rosso che lascia intravedere, soprattutto nella parte apicale, il contesto giallo vivo, si macchia di bluastro al tocco.

Carne

Compatta, soda, di colore giallo-limone o giallo-oro, al taglio vira intensamente al bluastro solo nel cappello, nel gambo rimane immutabile.

• Odore: fruttato.
• Sapore: dolce.

Caratteri microscopici

Spore

10-16 x 4-6 µm, bruno-oliva in massa, gialle al microscopio, lisce, ellissoidali, fusiformi, con debole depressione soprailare,.

Distribuzione e habitat

Cresce nei boschi di latifoglia (Castanea sativa, Quercus ilex), in terreno neutro o debolmente acido, da giugno a settembre.

Commestibilità

Tossico, anche se incostante.
Varia sensibilmente a seconda del substrato di crescita.

L'avvelenamento è talvolta di lieve entità, al punto da passare inosservato.

Tassonomia

Sinonimi e binomi obsoleti

• Boletus purpureus var. rhodoxanthus
• Boletus rhodopurpureus var. rhodoxanthus (Krombh.) Bon, Documents Mycologiques 15(no. 60): 38 (1985)
• Boletus sanguineus var. rhodoxanthus Krombholz

Specie simili

Può essere confuso con:

• Boletus rhodopurpureus, anch'esso velenoso, che ha sul cappello tonalità rossastre omogenee, senza sfumature biancastre e la carne virante intensamente al bluastro in tutte le sue parti e non solo nel cappello come avviene nel Boletus rhodoxanthus.
• Boletus satanas, che ha carne giallo pallido, che vira all'azzurro con la stessa intensità nel gambo e nel cappello, l'odore cadaverico e il gambo di solito più ingrossato alla base.

Bibliografia

• (EN) Boletus rhodoxanthus, in Index Fungorum, CABI Bioscience.
• Boletus rhodoxantus su www.fungoceva.it, su fungoceva.it.
• Galleria fotografica su www.interhias.de, su interhias.de.
• Galleria fotografica su www.micologia.net, su micologia.net.

Vos an lenga piemontèisa Për amprende a dovré 'l sistema dle parlà locaj ch'a varda sì.

Capel fin a 20 (o 25) cm, sliss peui finiment tomentos, biancastr con tonalità giaunastre, òcra e soens reusa, almanch al bòrd. Tùboj giaunastr peui oliva, a ven-o un pòch bleu al taj. Përtus giàun peui da ross groson a ross sangh, a ven-o bleu al toch. Gamba àuta fin a 16 cm e larga fin a 8 cm, giàuna motobin viva, ross sangh o vinos an bass, tuta coatà da un retìcol a maje longhe e pontinà ëd ross peui brun ross. Carn giàuna cròm viv o saturà, an gavand ël pé (rossastr), a ven un pòch bleuva al taj, dossa.

Ambient

A chërs sota latifeuje.

Comestibilità

A venta mai mangé un bolè trovà se un a l'é nen un bon conossidor dij bolè!
As peul nen mangesse.

Arferiment bibliogràfich për chi a veul fé dj'arserche pì ancreuse

Boletus rhodoxanthus (Krombholz) Kallenbach

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Rožnatoglavi goban, imenovan tudi rdečerumeni goban ali rožnati goban (znanstveno ime Boletus rhodoxanthus) je pogojno užitna goba iz rodu gobanov.

Opis

Ta gobja vrsta na videz malce spominja na vražji goban, a se od njega loči po citronasto rumenem mesu, ki na prerezanih mestih takoj pomodri in rožnatem klobuku, po katerem je dobila slovensko ime.

Klobuk tega gobana je sprva izbočen, pozneje pa postane blazinasto zaobljen in doseže do 20 cm v širino. Na temenu je klobuk belo sivkast do bledorumenkast, proti robovom pa prehaja v rožnato barvo. Cevke himenija so sprva rumene, nato pa postanejo rumeno zelene in imajo temno karminske luknjice. Himenij na prerezanem mestu tudi takoj pomodri, v njem pa je olivno rjav trosni prah, v katerem so vretenasti, 10-16 x 5-6 mikronov veliki trosi.

Bet je pri mladih primerkih trebušast pri starejših pa se razpotegne in je večinoma vitek v dnišču pa zadebeljen. Rumeno osnovo beta pokriva karminsko rdeča mrežica s fino teksturo, ki je v dnišču izrazeitejša. Meso v betu je čvrsto in citronasto rumeno, a prerezano manj izrazito pomodri. Vonj gobe ni izrazit, okus pa je precej mil.

Razširjenost in uporabnost

Pri nas je ta vrsta gobanov precej redka in zato zavarovana, najdemo pa jo lahko na apnenčastih tleh, pod listavci (predvsem hrasti in bukvami), v toplih poletnih dneh.

Surov rožnatoglavi goban je strupen in povzroča prebavne motnje, prekuhan pa je sicer užiten, a ni preveč dobrega okusa. Velja za eno najbarvitejših evropskih gobjih vrst. Še najbolj podoben mu je temnoškrlatni goban (Boletus rhodopurpureus), ki raste v podobnem okolju.

Glej tudi

• queletov goban
• svinjski goban