Butyriboletus roseopurpureus (Both, Bessette & Roody) Kuan Zhao, Zhu L. Yang & Halling, 2015

Butyriboletus roseopurpureus (Both, Bessette & Roody) Kuan Zhao, Zhu L. Yang & Halling View in CoL , comb. nov. Fig. 4a–d View FIGURE 4

MycoBank: MB 812759

Basionym: Boletus roseopurpureus Both, Bessette & Roody , North American Boletes, A Color Guide to the Fleshy Pored Mushrooms (Syracuse): 150, 2000

Pileus 7–15 cm in diameter, convex, becoming broadly convex to nearly plane in age, margin incurved at first, later decurved; surface viscid-tacky in wet weather but drying quickly, velvety-tomentose at first, becoming appressed-tomentose to fibrillose, the fibrils darker, narrow; a striking pinkish purple when fresh, becoming dark purplish pink to dark purplish red, at times somewhat mottled in these colors, the marginal areas becoming grayish in age; context pale yellow, instantly dark blue when exposed but soon fading to pale slate color. Hymenophore surface at first lemon yellow or more golden, becoming yellowish olive to greenish olive at maturity, instantly dark blue to greenish blue when bruised, soon fading to pale greenish blue or greenish gray; pores circular, 1–2 per mm; tubes 5–10 mm deep, concolorous with the surface, bluing rapidly when injured. Stipe 4.5–8.5 × 2–4 cm, equal or slightly tapered downwards, reticulated near the entire length, or at least over the upper two-thirds, and the lower third appressed-tomentose, the reticultion in part strongly raised; bright yellow over most of the length of the stipe, occasionally with burgundy red areas near the base; surface instantly staining dark blue when bruised; context deep yellow, in basal areas burgundy red in some specimens, instantly bluing when exposed but soon fading to pale slate color; basal mycelium white. Odor fragrant. Taste very sour, like lemon ( Bessette et al. 2000).

Basidiospores [60/2/2] (9) 10–13 × (3) 3.5–5 μm [Q = 2.20–2.88 (3.00), Q m =2.59 ± 0.24], subfusiform, subhyaline in KOH. Basidia 24–35 × 6–10 μm, clavate, hyaline in KOH, 4-spored. Hymenophoral trama boletoid. Pleurocystidia 32–44 × 10–15 μm, smooth and thin-walled, hyaline in KOH, lageniform to fusoid-ventricose; cheilocystidia similar to pleurocystidia in shape but smaller. Pileipellis composed of interwoven hyphae 4–6 μm in diameter, smooth, thin-walled, hyaline; end cells not differentiated. Clamp connections absent.

Habitat: Solitary or in small groups in mixed woods of oak, beech, hemlock and maple.

Known distribution: Known from eastern North America.

Materials examined: USA. New York, Erie County, Chestnut Ridge Park , 27 July 1995, E.E. Both 3765 ( BUF, type) ; Tennessee, Great Smoky Mountains National Park , 24 Jul 2008, DLJ-TN-08-17 ( NY 01042656 ) .

Notes: Bessette et al. (2000) separated B. roseopurpureus from B. speciosus (1874: 2) on account of its pileal surface with purplish tone and the smaller spores. However, according to a recent study ( Arora & Frank 2014), the ITS sequences obtained from several collections of Bu. roseopurpureus are identical to those of Boletus speciosus collections from TENN sequenced by Li et al. (2014). Due to the lack of well dried specimens and sequences of tef1-α and rpb1 of B. speciosus for a multi-gene analysis, its systematic position can only be settled in the future.