Cyanoboletus bessettei A.R. Bessette L.V. Kudzma, & A. Farid sp. nov.
MycoBank number: MB 840857: Index Fungorum number: IF 840857; Facesoffungi number: FoF 10466;
Pileus 2.7–8 cm broad, convex with an incurved margin that remains into maturity; surface subtomentose to nearly glabrous, dry, buffy brown overall when very young, becoming paler toward the margin and retaining darker brownish coloration on the disc at maturity, staining blue-green then dark olive-green and finally brown when bruised; margin with a narrow band of sterile tissue, sometimes undulating or lobed in age; context pale yellow, staining blue-green then slowly turning peach to dull pinkish orange when exposed; odor unpleasant, odd, chemical-like; taste slightly acidic or not distinctive. Cuticle stains dark amber with the application of KOH, pale olive with FeSO4, and amber with an expanding blue-green outer ring with NH4OH. Context stains yellow, then pale orange with the application of KOH or NH4OH and is negative with FeSO4. Hymenophore tubulose, pale yellow, staining blue-green, then olive when bruised; pores angular to irregular, 2–3 per mm; tubes 4–8 mm deep. Stipe 2.5–4 cm long, 1–2 cm thick, nearly equal or flaring at the apex, pinched at the base; surface longitudinally striate, dry, distinctly pale yellow at the apex, reddish brown below, with white basal mycelium, staining blue-green then reddish-brown; context pale yellow, slowly staining blue-green at the apex, then becoming bright chrome yellow.
Basidiospores olive-brown in fresh deposit, (8–)9–11(–12) × 3.5–5 µm, n = 30, Q = 2.30, narrowly ovate to subelliptic in face view, obscurely inequilateral in profile, thin-walled, smooth, lacking an apical pore, yellowish in KOH or Melzer’s, inamyloid; spores sometimes collapsing when mounted in Melzer’s. Basidia 23–36 × 5.5–9 µm, mostly clavate, few cylindro-clavate, (2)4-sterigmate, hyaline in KOH, grayish yellow in Melzer’s. Basidioles 19–31 × 5–8.5 µm, clavate. Hymenial cystidia abundant, sometimes in fascicles, 36–51 × 8–11 µm, ventricose-rostrate, some with and elongated neck, thin-walled, smooth, yellowish in KOH, non-reactive in Melzer’s. Hymenophoral trama boletoid, with lateral elements, 3.5–7 µm, wide, moderately divergent, hyaline to grayish yellow in KOH or Melzer’s. Pileipellis a tangled layer of repent tubular hyphae, 3.5–5.8 µm wide, with cylindrical, rounded end cells, thin-walled, smooth, hyaline to grayish yellow in KOH, yellowish in Melzer’s. Pileus trama hyphae loosely interwoven, 4.5–13 µm, smooth, thin-walled, hyaline in KOH, yellowish in Melzer’s. Stipitipellis hyphae mostly parallel, slightly interwoven, 3–6.5 µm, hyaline in KOH, yellowish in Melzer’s. Stipe trama subparallel, interwoven, 5.2–14 µm, hyaline in KOH, yellowish in Melzer’s. Caulocystidia none observed. Clamp connections absent.
Material examined: USA, South Carolina, Berkeley County, Francis Marion National Forest, State Route 402, approximately 1.25 mi. north of Huger, under oak and pine, 17 Sep 2016, A.R. Bessette ARB1393 (Holotype USF 301500).
Distribution: Scattered or in groups in sparsely grassy areas and sandy soil in association with Quercus and Pinus in fall (September), in southeastern United States, known only from South Carolina.
Sequence data: ITS: MW675734.1 (ITS1/ITS4); LSU: MW662571.1 (LROR/LR5); EF1a: MW737482.1 (EF1-BF1/EF1-B-R); RPB1: – (RPB1-B-F/RPB1-B-R); RPB2: MW737457.1 (RPB2-B-F1/RPB2-B-R)
Notes: The combination of distinctive staining reactions and very small spore size is distinct. To date, it is known only from the type location in southeastern South Carolina, United States. Caloboletus inedulis (Murrill) Vizzini is superficially similar with a pale yellow hymenophore that becomes olive yellow at maturity and stains dark blue then brownish when bruised. It has a reticulated pale-yellow stipe that may have pinkish tones at the apex and/or pinkish tints below, and bitter tasting context.
Figure 3 – Field photograph of Cyanoboletus bessettei (ARB 1393). Photo credit: A.R. Bessette.