Boletales » Boletaceae » Paxilloboletus

Paxilloboletus africanus

Paxilloboletus africanus Badou, De Kesel & Yorou, in Badou et al., Mycological Progress 21(1): 247 (2022)

Etymology: refers to its distribution throughout tropical Africa.

Basidiomata epigeal, solitary or in small groups of 23, pileate; hymenophore lamellate, bifurcating, anastomosing, decurrent, sometimes leaving fine, low ridges or a thin network on the upper stipe, centrally stipitate, putrescent, gymnocarpic. Spore print yellowish brown. Pileus 3075 mm diam., convex, with incurved margin at first, becoming slightly depressed in center, entirely smooth, sometimes ruptured or cracked at maturity, tomentose to velvety, dry, matte, at first pure white, showing fine yellowish-brown fibrils (hand lens!), becoming cream to slightly yellowish (2A23A2), margin concolorous, persistently incurved or rarely straight, wavy, smooth, tomentose.Stipe 2035(45) × 1012(15)mm, cylindric, tapering downwards, shorter than pileus diameter, smooth, rarely tomentose, matte, at first white to yellowish white, becoming cream to yellowish (2A23A2), sometimes finely ridged or beset with a network in upper third, non-rooting; basal mycelium white, clasping soil, sometimes with fine mycelial strands. Lamella decurrent, easily separable from pileus context, narrow, up to 45 mm high at mid radius, often crowded, arcuate to straight, frequently forked (14 ×), often anastomosing or with distinct interconnecting veins near the stipe, yellow (2A57), becoming yellowish brown with age (5DE67), edge smooth and concolorous, unchanged when bruised, dark blackish blue with Melzers reagent. Context 36 mm thick in the center of the pileus, gradually thinner toward the margin, pure white throughout, becoming dirty yellowish white in the stipe of older specimens, unchanging when exposed. Context strongly amyloid (Melzers reagent), at least in lamella (especially the hymenium itself). Taste fungal, insignificant. Odor feeble, insignificant.

Basidiospores (7.3–)7.68.910.2(–11.1) × (3.8–)3.94.44.8(− 5.1)µm with Q = (1.66–)1.722.042.36(–2.45) {N = 381; all 6 collections} and (7.3–)7.38.49.5(–9.9) × (3.9–)44.54.9(–5.1)µm with Q = (1.66–)1.651.872.09(–2.37) {N = 101; only holotype SAB0716}, ellipsoid to slightly fusiform, sometimes with a slight adaxial (supra-hilar) depression, thin-walled, smooth under SEM, with a small hilar appendage, without apical pore, slightly cyanophilic, slightly amyloid (grayish walls). Basidia clavate, (27.3–)47.6 × (7.9–)11.7 µm, hyaline, 4-spored, sterigmata 3.84.3(5.2) µm long. Pleurocystidia (54.5–)91.2 × (8.4–)13.2 µm, frequent, born deep in subhymenium, mostly fusiform, rarely septate in the lower third, with rounded apex, hyaline, thin walled, smooth, inamyloid. Gill edge mostly fertile, caulo- and cheilocystidia less frequent, (57.5–)75.7 × (8.9–)11.2 µm, similar to pleurocystidia.Lamellar trama divergent near pileus, with compact mediostratum and gelatinized lateral strata, subregular to regular toward the lamella edge, in the center composed of thin-walled, hyaline hyphae (diam. 45 µm) with locally roughened surface, beneath the subhymenium mixed with conspicuously inflated (diam. 816 µm) hyphae, constricted at the septa. Pileipellis a tomentum composed of intermixed, hyaline and pigmented hyphae, all smooth, thin-walled, with cylindrical, non-inflated end-cells of 5.29.8 µm diam; the pigmented pileal hyphae normally septate, filled with a yellowish to pale brownish thrombomorphic deuteroplasm, unchanged in KOH, becoming only slightly browner in Melzers reagent. Stipitipellis in the upper part of the stipe with sparse hymenial elements, elsewhere composed of parallel hyphae supporting a collapsed tomentum, similar to the pileipellis. Clamp-connections absent in all tissues.

Ecology and distribution: Thus far collected in West Africa, specifically Benin (gallery forest with Berlinia grandiflora and Uapaca guineensis), Togo (miombo forest with Uapaca togoensis and Monotes kerstingii) and Guinea (woodland with Isoberlinia spp., Uapaca togoensis and Anthonotha crassifolia); in Central Africa, specifically the Democratic Republic of the Congo (miombo dominated by Julbernardia globiflora) and Zambia (soil and relic miombo woodland); and in East Africa in Tanzania (primary miombo forest). It is also known in Madagascar from sequence data (EcM root tip of Uapaca bojeri in littoral forest).

Index Fungorum number: IF840711