Cyanoboletus cyaneitinctus (Murrill) A. Farid, A.R. Franck & J.A. Bolin comb. nov.

MycoBank number: MB 840858; Index Fungorum number: IF 840858; Facesoffungi number: FoF 10465;

BasionymCeriomyces cyaneitinctus Murrill, Lloydia 6: 225 (1943).

Synonyms – Boletus cyaneitinctus (Murrill) Murrill, Lloydia 6: 228 (1943).


Pileus 3–8 cm wide, pulvinate or convex when young becoming broadly convex at maturity, bister, umber, mahogany, and dark brown overall, rarely entirely red in the pileus, glabrous to tomentose, tacky when wet, sometimes rimulose at maturity, blackening instantly where handled. Hymenophore tubulose, yellow, darkening to a gold color when mature, tubes 5–20 mm long, bluing instantly and strongly when handled; pore mouths subangular when mature, 0.5–1 mm in diameter. Stipe 3–6 × 0.5–2 cm, equal to ventricose, bright yellow, smooth or sometimes reticulate on the upper third, sometimes with flushes of reddish to brownish-red floccons, particularly towards the base of the stipe, bluing instantly and strongly when handled, basal mycelium white to yellowish white. Context concolorous with stipe surface, often with red pigments at the very base of the stipital context, blueing instantly and strongly, fading to pale yellow. KOH on pileus dark maroon to black, red elsewhere; FeSO4 negative, erasing blue stains from flesh.

Basidiospores (11) 11.5–15 (16) × 4–6 μm, n = 30, Q = 2.4, fusiform, sometimes with a suprahilar depression present. Basidia 25–50 × 8–10 µm, 4-spored, thin-walled, hyaline, clavate to pyriform; sterigmata 1–2 μm, occasionally pigmented like pleruocystidia. Basidioles similarly sized and shaped. Pleurocystidia 30–60 × 7–10 µm, fusoid to ampullaceous, hyaline or sometimes encrusted. Cheilocystidia similar to pleurocystidia. Pilepellis a trichodermium of strongly interwoven, filamentous, sinuous, rarely branched hyphae, erect or repent in most of the terminal elements, collapsing into a cutis, terminal elements cylindrical, apices rounded or somewhat pointed, 20–70 × 5–10 μm, smooth-walled, inamyloid, hyaline to golden-yellow or somewhat brownish in water and 5% KOH. Clamp connections absent.

Material examined: USA, Florida, Alachua Co., Gainesville, 2 Oct 1949, W.A. Murrill s.n. (FLAS F16163); ibid., lawn under pecan [Carya illinoinensis], 7 Nov 1947, W.A. Murrill s.n. (FLAS F40835); ibid., Kelley’s Hammock, 3 Aug 1938, West and W.A. Murrill s.n. (holotype FLAS F17986); ibid., yard at 936 NW 30th Ave., 9 Aug 1980, G.L. Benny s.n. (FLAS F52704); ibid., lawn under laurel oak [Quercus laurifolia], 1 Aug 1947, Murrill s.n. (FLAS F19093); ibid., shaded yard, 6 Nov. 1950, R. Bennett s.n. (FLAS F59706); ibid., lawn der hardwoods, 13 Oct 1950, R. Bennett s.n. (FLAS F19647); ibid., 19 × 1950, R. Bennett s.n. (FLAS F 40863); ibid., lawn on 18th block of NW 11 place, Sept 12 1968, J. Kimbrough s.n. (FLAS F48020); ibid., under large live oak [Quercus virginiana] 10 mi. SE of Gainesville, on Palatka Rd., 2 Nov 1947, G.F. Weber s.n. (FLAS F40837); Hillsborough Co., Alafia River State Park, 17 Jul 2018, J. Bolin 177 (USF 300090); Hillsborough County, Tampa, University of South Florida Tampa Campus, entrance area off of Leroy Collins Boulevard, 11 Jun 2016, A. Farid 340 (USF 288424); USF campus, 22 May 2018, Franck 4352 (USF 297911); Tampa, Learning Gate Community grounds, 4 May 2019, A. Farid 920 (epitype USF 301499); Palm Beach Co., Frenchman’s Reserve, 1 III 2019, J. Bolin 324 (USF 300081); Prosperity Oaks, 2 Mar 2019, J. Bolin 325 (USF 300080). OHIO: Hocking Co., 4 Aug 2018, J. Bolin 185 (USF 300091); Vinton Co. 5 Aug 2018, J. Bolin 184 (USF 300085). TENNESSEE: Knox Co., Knoxville, Tobler Rd., 4 Sept 1949, A.J. Sharps s.n. with L.R. Hesler (FLAS-F-53755).

Distribution: Basidiomes typically occurring singly or more rarely gregariously, widely distributed in eastern North America.

Sequence data: ITS: MW675744.1 (ITS1/ITS4); LSU: MW662579.1 (LROR/LR5); EF1a: – (EF1-BF1/EF1-B-R); RPB1: MW737503.1 (RPB1-B-F/RPB1-B-R); RPB2: MW737465.1 (RPB2-B-F1/RPB2-B-R)

Notes: Cyanoboletus Gelardi, Vizzini, & Simonini is in the Pulveroboletus clade, and is comprised of eight species. Cyanoboletus was described in 2014 (Vizzini 2014) with Boletus pulverulentus Opat. as the type species for the genus. Alhough no molecular analysis was provided in the protologue, previous molecular analyses demonstrated several species (now in Cyanoboletus) were not related to Boletus L. s. str. (Gelardi et al. 2013, Wu et al. 2014). Cyanoboletus is distinguished from other boletoid genera by its yellowish brown to dark brown pileus, rapidly blueing context and hymenophore, and smooth basidiospores.

Cyanoboletus cyaneitinctus is very similar to the closely related C. pulverulentus (Opat.) Gelardi, Vizzini & Simonini. Both are boletes with a dark brown pileus, small pores (1–2 per mm), and yellow stripes with brown punctae; all surfaces instantly bruise blue. The European name has historically been applied to this species in North America (Singer 1947, Smith & Thiers 1971, Bessette et al. 2000, 2017), but we are here treating them as separate species based on our molecular analyses (Fig. 1) and morphological studies. The spore quotient Q is lower in C. cyaneitinctus at Q = 2.4 (with the Q usually between 2.3–2.5) compared to 2.6–2.9 in C. pulverulentus (Gelardi et al. 2013). These two species are geographically separated, with C. cyaneitinctus occurring in eastern North America and the latter found in Europe. Cyanoboletus sinopulverulentus, which is sister to C. cyaneitinctus (Fig. 1) is distinguished from C. cyaneitinctus and C. pulverulentus by its evenly dark brown stipe (lacking the reddish and yellow tones often present in the other two species), which is more heavily pruinose to scissurate. Cyanoboletus sinopulverulentus has predominately 2-spored basidia (4-spored in the other two taxa) and can also be distinguished on the basis of its Q value, which is reported as 2.17–2.45 (Gelardi et al. 2013), smaller than either of the other two Cyanoboletus species mentioned here.

Boletus mutabilis Morgan is an earlier but illegitimate name for this American species (see Art. 53.1). Thus, the oldest name we have to apply to the North American species is C. cyaneitinctus. Singer (1947) treated C. cyaneitinctus as a synonym of C. pulverulentus. The type of C. cyaneitinctus was examined, and matched the other North American collections examined. This type material is quite old and not in good condition; thus, we have designated an epitype, and have included images (Figs 4, 5A–G) as well as published molecular data. Cyanoboletus cyaneitinctus and C. pulverulentus are difficult to distinguish morphologically.

Figure 4 – Field photographs of Cyanoboletus cyaneitinctus. A A. Farid 920. B A. Farid 340. Macrochemical tests of basidiomes are labelled. The scale in the top is in centimeters. C JAB 324. D JAB 389. Photo credits: J.A. Bolin.