Fomitiporia rondonii Alves-Silva & Drechsler-Santos, sp. nov.

Index Fungorum number: IF 900085; Mycobank number: MB 900085; Facesoffungi number: FoF 13979; Fig. 1

Etymology – rondonii, named in honor of Marechal Cândido Mariano da Silva Rondon (1865–1958), a nominated for the Nobel Peace Prize in 1957, by his scientific and cultural contribution to the region in which this species occurs, through expeditions in 1900–1930.

Holotype – FLOR 58557

White-rot fungus found growing ondead unidentified angiosperm. It is currently known in Brazil, in the Cerrado and Xingu-Tapajós Provinces, Mato Grosso state. Basidiomata perennial, pileate, sessile, semicircular, obtriquetrous to triquetrous, occasionally concave, projecting 42–115 mm, 41–160 mm wide, and 25–85 mm thick at the base, with a woody consistency. Pileus glabrous, concentrically zonate with multiple narrow bands and up to 6 broad bands, moderately sulcate, faintly to strongly cracked, dull, dark brown [7F (4–8)] to black, greenish by algae and greyish to whitish in older basidiomata. Margin round, folded, thick, sterile, light orange [5A(5–6)] to golden brown, light brown, yellowish brown [5D(6–8)]. Pore surface greyish brown, brownish grey [7F (2–3)], dark brown [7F(4–5)] to cinnamon; pores round to angular, (5–)6–9(–10)/mm, (122–)127–155(–168) µm diam. (ave=141.46 µm); dissepiments entire, (59–)67–223(–238) µm (ave=102 µm) thick. Tubes distinct to mostly indistinctly stratified, with several layers, interleaved with context in older tube layers, brown [5EF (4–5)] to grayish brown (5E3), and the older layers filled with whitish mycelium. Context simple, up to 10 mm thick, concentrically zonate, with dense texture and with a woody consistency, brownish orange [6C (7–8)], light brown to brown [6DE (7–8)], with a distinct thicker dark line near to surface. Hyphal system dimitic in all parts; generative hyphae simple septate, hyaline to pale yellow, sparingly branched, 1.5–2.5 μm diam.; skeletal hyphae golden brown to reddish brown, unbranched,  thick-walled, in the context and hymenophoral trama 3–4.5 μm diam., the lumen 0.8–2.5(–2.8) μm wide. Hymenial setae absent. Cystidioles rare, fusoid, lanceolate, hyaline, and thin walled. Basidia subglobose to globose, hyaline, tetrasporic, 8–9(–10)×7–8 µm (ave=8.5×7.3 µm), Q=1–1.4 µm (aveQ=1.18 µm); basidioles identical in shape but slightly smaller than basidia. Basidiospores subglobose to globose, (4–)5–6×(4–)4.5–5(–6) µm (ave=5×4.8 µm), Q = 1–1.1 µm (aveQ = 1.2 µm), hyaline, moderately to strongly dextrinoid, cyanophilous, thick-walled, smooth. Crystals rhomboid, of variable size.

Material examined – BRAZIL, Mato Grosso: Cuiabá, Parque Nacional de Chapada dos Guimarães, Sítio Véu de Noiva, 15° 24′ 23.19″ S 55° 50′ 12.14″ W, on dead trunk, unidentified angiosperm, 8 Feb 2015, G. Alves-Silva 726 (FLOR 58557 holotype); ibid., Itaúba, Rio Teles Pires, 11° 03′ 54.2″ S 55° 19′ 25.2″ W, on dead standing unidentified angiosperm, 01 Apr 2017, M. E. Engels (ICN202298 paratype).

GenBank numbers – FLOR 58557 holotype (LSU: KU663295, ITS: KU663322, tef1-α: KU663346, RPB2: KU663371); ICN202298 paratype (LSU: OQ148660, ITS: OQ148661, tef1-α: OQ148662, RPB2: OQ148663).

Notes – Fomitiporia rondonii is characterized mainly by having obtriquetrous basidiomata, mostly indistinctly stratified tube layers, and greyish to whitish pileus in older basidiomata. Microscopically, basidiospores are moderately to strongly dextrinoid, 5×4.8 µm on average. Phylogenetically, this species was recovered in F. langloisii–F.castilloiclade, in which only F. castilloi, F. bambusipileata, and F. exigua (sp. nov. also proposed in this paper) are pileate species retrieved among all neotropical resupinate species. Fomitiporia castilloi differs by having hymenial setae and F. bambusipileata that only occurs on bamboo culm (Amalfi and Decock 2013; Alves-Silva et al. 2020a). Concerning the remaining neotropical pileate species, F. rondonii is morphologically closely related to the species of F. apiahyna s.lat. clade and F. subtilissima clade. Fomitiporia subtilissima has thinner and distinctly reddish brown pileate basidiomata. Fomitiporia nubicola and F. apiahyna differ by having particular ecological requirements, the former occurs exclusively on Drimys spp. in Cloud forests and the latter in Araucaria Forest province, at 800–1000 m.a.s.l. (Alves-Silva et al. 2020b), whereas F. rondonii appears to be restricted to Cerrado–Amazon distribution. Fomitiporia conyana and F. murrillii differ by having slightly bigger pores [F. conyana: 6–8(–9)/mm and F. murrillii: (4–)5–7(–8)/mm], moreover, F. murrillii also has slightly bigger basidiospores [5–6(–7)×5–6(–7) µm] (Alves-Silva et al. 2020b).

Figure 1 – Fomitiporia rondonii (FLOR58557, holotype) a Basidiomata in-situ. b Black line near to the surface. c Obtriquetrous basidioma, context, and indistinct tube layers. (ICN202298) d Whitish abhymenial surface. e Triquetrous basidioma. (FLOR58557, holotype) f Strongly dextrinoid basidiospore. (ICN202298) g–h Moderately to strongly dextrinoid basidiospores. Scale bars: a–e=30 mm, f–h=5 µm