Fulvifomes subthailandicus E. Arumugam, S. Gunaseelan, K. Kezo & M. Kaliyaperumal sp. nov.

Index Fungorum number: IF 900218; Mycobank number: MB 900218; Facesoffungi number: FoF 13988; Fig. 1

Etymology – The species epithet “subthailandicus”, signifies the close relation with the species Fulvifomes thailandicus.

Holotype – MUBL4025

Basidiocarp perennial, solitary, pileate, sessile, woody hard when fresh, woody hard and light weight when dry. Pileus dimidiate, meagrely ungulate, projecting up to 14 cm wide and 12.5 cm in length. Pilear surface radially cracked concentrically zonate, greyish brown (7D2) near the attachment to brownish grey (7F5) towards the margin. Margin entire, acute, velutinate, brown (7E7). Pore surface brown (7E5). Pores regular, round, 4–5 per mm. Context less than 1 mm, homogenous, brown (7F7). Tubes brown (6E7), 3.3 cm in length, tube layer stratified with intermittent context, each stratum up to 2 mm. Hyphal system dimitic, tissue darkening with KOH without swelling. Context generative hyphae thin to thick-walled, hyaline to dark brown, simple septate, rarely branched, 2.5—5.2 µm dia., skeletal hyphae, thick walled with narrow to wide lumen, brown, aseptate, unbranched, 3.9—4.5 µm dia. Tramal generative hyphae thin to thick walled, hyaline to dark brown, simple septate, rarely branched, 2.5–5 µm dia., skeletal hyphae, thick walled with narrow to wide lumen, brown, aseptate, unbranched, 3.9–4.4 µm dia. Setae and cystidioles absent. Basidia clavate with four sterigmata, 9–10.8×3–5.8 µm. Basidioles clavate, 9–10.2×3.3–5.8 µm. Basidiospores thick walled, subglobose to broadly ellipsoid, pale yellow to golden yellow in water, turning brown in KOH, smooth, (5.2–) 5.4–5.9 (–6.2)×(4.9–) 5.2–5.4 µm (n=30/2), IKI−, CB−, Q=1.15 (Q range 1.1–1.15).

Material examined – India, Tamil Nadu, Villupuram District, Nedimozhiyanur, 1208′ 24.45″ N 7833′ 38.05″ E on a dead wood of Prosopis juliflora, 14 September 2021, Elangovan Arumugam (MUBL4025, holotype).

Additional Material examined – India, Tamil Nadu, Villupuram District, Nedimozhiyanur, 1208′ 24.38″ N 7833′ 38.26″ E on a dead wood of Prosopis juliflora, 24 December 2023, Elangovan Arumugam (MEII2_2, Paratype).

GenBank numbers – ITS: OQ062657; LSU: OQ064102 (MUBL4025, holotype); ITS: PP827158; LSU: PP816284 (MEII2_2, Paratype)

Notes – The ML and Bayesian analyses revealed that F. subthailandicus formed a new linage that shares a sister clade with F. grenadensis (726% ML, 0.9 BYPP), F. thailandicus (56% ML, 0.54 BYPP), F. hainanensis (97% ML, 1.0 BYPP). Fulvifomes subthailandicus is similar to F. thailandicus by having a cracked and concentrically zonate pilear surface, dimitic hyphal system but the later differs with the presence of cystidioles, smaller pores (6–7/mm) and basidiospores ((5–) 5.2–6.2 (–6.4)×(4–) 4.8–5.1 µm) (Zhou 2015). Fulvifomes subthailandicus shares similar characteristics with F. grenadensis by having concentrically zonate pilear surface, homogeneous context, lacks cystidioles, and stratified tubes but the later differs by having smaller pores (4–7/mm) and basidiospores (5–6.4×4–5.1 µm) (Ryvarden 2004). Our Indian species shares similar morphological and microscopic characteristics with F. hainanensis by having velutinate pileus, dimitic hyphal system and absence of cystidioles and setae but the later differs by the presence of uncracked pilear surface, obtuse margin, duplex context, larger pores (3–4/mm) and slightly smaller spores (5–6.4×4–5.1 µm) (Zhou 2014). Our macro-microscopic illustrations were consistent with the phylogenetic analyses inferred from the combined dataset of ITS and nLSU of Fulvifomes spp.

Figure 1 – Fulvifomes subthailandicus (MUBL4025, holotype) Microscopic structures of Fulvifomes subthailandicus (drawn from the holotype). a Basidiomata. b Pilearsurface. c Pore surface. d Context. e Stratified tube layer. f Tramal hyphae. g Context hyphae. h Basidioles. i Basidia. j Basidiospores k. phloxine. l Water. m Cotton blue. n Melzer. Scale bars: c=1 mm, d–e=10 mm, f–n=10 µm