Rubroboletus latisporus Kuan Zhao et Zhu L. Yang, 2014

Zhao, Kuan, Wu, Gang & Yang, Zhu L., 2014, A new genus, Rubroboletus, to accommodate Boletus sinicus and its allies, Phytotaxa 188 (2), pp. 61-77 : 68-70

Rubroboletus latisporus Kuan Zhao et Zhu L. Yang , sp. nov. ( Figs. 3–4 )

MycoBank: MB 809242

Etymology: latisporus refers to the broad spores.

Holotype: — CHINA. Chongqing Municipality : Wu County, on the ground of a mixed forest dominated by Pinus massoniana , 950 m, 5 Jul 2013, Lihong Han 128 ( HKAS 80358 , holotype!).

Pileus 7–10 cm in diameter, hemispherical to convex; surface blood red (10D7–8), strongly viscid when wet and shiny when dry, becoming dark blue when bruised; context 1–1.5 cm thick, whitish to white (1 A 1) to cream-colored (4 A 2), becoming blue promptly when injured, then back to the original color slowly. Hymenophore depressed around stipe, surface orange-red (5 B 6–8) to yellow (2 A 6–8) when mature, rapidly bluing when bruised; pores angular, 2–3/mm; tubes up to 1 cm in depth, yellow (3 B 7–8) to olivaceous green (30 C 5–7), becoming blue very quickly when injured, then back to the original color slowly. Stipe 8–10 × 2–2.5 cm, sub-cylindrical, robust, tapering upwards, background yellow (4 A 7–8), reticulum confined to the upper part and concolorous with the stipe; spots dark red (11D7–8) to brown-red (12 E 6–8), irregularly distributed over nearly the entire stipe; mycelia at the base of the stipe white; context yellowish (3 A 2–3), turning blue quickly when injured, then back to the original color slowly. Odor and taste indistinct.

Basidiospores [80/2/2] (9.5) 11–13 (14) × 6–6.5 (7) μm, [ Q = (1.83) 1.91–2.15 (2.17), Q m =2.02 ± 0.06], ovoidellipsoid, nearly colorless in KOH and yellowish brown in Melzer’s reagent. Basidia 24–39 × 8–12 μm, clavate, 4-spored, sometimes 2-spored. Cheilocystidia 39–62 × 6–10 μm, narrowly lageniform to lageniform, thin-walled, colorless in KOH. Pleurocystidia similar with cheilocystidia in shape and size. Pileipellis an interwoven trichoderm composed of more or less vertically arranged thin-walled, filamentous hyphae 3.5–5 μm in diameter, embedded in a gelatinized matrix. Stipe trama composed of vertically arranged hyphae. Clamp connections absent in all tissues. Amyloid reaction none.

Habitat and distribution: Solitary or in groups under Pinus massoniana or in mixed forests of Pinus spp. and Quercus spp. Currently only known from southwestern China.

Paratype: CHINA, Yunnan Province: Shilin County, Gui Mountain, in a mixed forest dominated by Pinus and Quercus , alt. 2200 m, 8 Aug 2010, Gang Wu 286 ( HKAS 63517).

Notes: Rubroboletus latisporus is characterized by its strongly viscid pileus when wet, brown-red spots on the stipe and broad spores. This species is closely related and similar to R. dupainii , originally described from France, as they share the vivid red and gelatinized pileus. However, the surface of the hymenophore of R. latisporus is orange-red to yellow when mature, while that of R. dupainii is blood red to dark red. Furthermore, the context of the former is whitish to cream-colored, while that of the latter is pale yellow (3 A 3).

Figures

FIGURE. 3. Basidiomata of Rubroboletus latisporus (holotype). a. Mature basidioma. b. Bluish color change after injury (image taken immediately after sectioning). Bars: a–b=2 cm.

FIGURE. 4. Microscopic features of Rubroboletus latisporus (holotype). a. Basidiospores. b. Basidia and pleurocystidium. c. Cheilocystidia. d. Pileipellis in a gelatinized matrix. Bars: a=10 μm; b–d=20 μm.