Fulvifomes thiruvannamalaiensis Gunaseelan, S., Kezo, K. and Kaliyaperumal, M., sp. nov.

MycoBank number: MB 558486; Index Fungorum: IF 558486; Facesoffungi number: FoF 10726; Fig.1

Etymology: The species epithet “thiruvannamalaiensisreferring to the locality of basidiomata collection.

Holotype: MUBL4013

Description: Basidiocarp perennial, solitary, sessile, applanate, broadly attached to the substrate by the narrow side, hard, woody when dry. Pileus dimidiate, convex to meagrely ungulate, lacks crust, projecting up to 4.8 cm length, 10.4 cm width and 3.4 cm thick near the attachment. Pilear surface partly covered with micro algae, glabrous, light brown (6D8, 6E7), rust brown (6E8) to dark brown (6F7), finely cracked with small brownish grey scales (6E3, 6F2) concentric and radially sulcate, but coarse and deep sulci, scrupose zones near the attachment/older region, meagrely wavy near the margin. Margin entire, round to obtuse, velutinate to smooth, dark brown (6F7), brownish grey (6F2), often wavy. Pore surface yellowish raw umber brown (5F8), yellowish brown (5E8) to brown (6E7, 6F8). Pores round, regular, 4–7 per mm.  Dissepiments entire, thick. Context up to 1.6 cm, homogeneous, fibrous to corky, brown (6E7, 6F8) to dark brown (6F7). Tubes yellowish brown (5E8), light brown (6D6) to brown (6E7, 6F8), up to 1.3 cm thick, tube layers stratified with thin walled bright yellowish generative hyphae usually running between the old tubes, each stratum up to 0.4 cm.

Hyphal system strictly dimitic, skeletal and generative hyphae acyanophilous; tissue darkening with KOH without swelling. Context Generative hyphae dominant, thin to thick walled, simple septate, branched, hyaline to brown, 1.2–4.8 μm diam.; skeletal hyphae, thick-walled with narrow to wide lumen, unbranched, aseptate, yellow to brown, 2.4–4.3 μm diam. Trama Generative hyphae, thin to thick walled, septate, rarely branched, hyaline to brown, 1.2–4.8 μm diam.; skeletal hyphae, thick walled with narrow to wide lumen, aseptate, unbranched, brown, 2.4–4.8 μm diam. Setae absent. Cystidioles thin walled, hyaline, varies in shape, fusoid to ventricose with elongated apical portion, 12.9–27 × 2.8–7.2 μm. Basidioles clavate to broadly clavate, 8.5–15.5× 3.5–6.5 μm. Basidia clavate to broadly clavate, with four sterigmata, 9.4–15.7× 5.2–8 μm. Basidiospores broadly ellipsoid to subglobose, thick-walled, smooth, yellow in water, turning brown in KOH, (5.3–) 5.5–6.7 (–6.9) × (4.6–) 4.8–5.1(–5.5) μm (n = 30/2), Q = 1.05–1.3, CB ̄, IKI ̄.

Material examined: INDIA, Tamil Nadu, Thiruvannamalai district, Jawadhu hills, Jamunamarathur, 12.64º 54’19.1”N 79º 18’33”E, on living angiosperm tree (Albizia amara), 09 Febraury 2018, Sugantha Gunaseelan (Holotype, MUBL4013).

GenBank numbers: ITS: MZ221598; LSU: MZ221600

Notes: Fulvifomes thiruvannamalaiensis, characterized by perennial, solitary, dimidiate, applanate to ungulate basidiomes, significantly cracked pilear surface with brownish grey scales, stratified tube layer with dimitc hyphal system and thick walled yellow to brown, acyanophilic subglobose to ellipsoid basidiospores.

African species, F. yoroui (Olou et al. 2019) shows close resemblance with F. thiruvannamalaiensis, in sharing perennial, pileate, ungulate basidiomata, dimitic hyphal system and presence of fusoid cystidioles, but the size and shape of the basidiospores (subglobose to globose basidiospores 5.5–6.5 × 4.7–5.6 μm), differ from F. thirvannamalaiensis. F. krugiodendri (Ji et al. 2017), F. rimosus (Hattori et al. 2014) and F. thailandicus (Zhou 2015) are closely similar with F. thirvannamalaiensis morphologically by sharing dimidiate, concentrically sulcate, cracked basidiocarp, dimitic hyphal system and presence of fusoid cystidioles, yet differs in number of pores and the size of basidiospores

Despite few morphological resemblances between F. elaeodendri (Tchoumi et al. 2020) such as sulcate, glabrous pileus becoming cracked with age, stratified tube layer the distinct microscopical traits viz., absence of cystidioles and the size of the basidiospores are distinguishing F. thiruvannamalaiensis from F. elaeodendri. F. centroamericanus (Ji et al. 2017), F. hainanensis (Zhou 2014) and F. imbricatus (Zhou 2015) besides having dimitic hyphal system, significantly distinct from F. thiruvannamalaiensis in morphology and microscopic features, by having uncracked pilear surface, shape and size of basidiospores.

Fulvifomes thiruvannamalaiensis shares a few similar morphological traits with the American species F. cedrelae, F. robinae and F. squamosus (Salvador-Montoya et al. 2018) by having perennial, applanate, ungulate, sessile basidiomata with sulcate, cracked pilei, homogenous context and stratified tubes, however the former differs from the later in hyphal system, number of pores and size of the basidiospore. The Chinese species F. submerrillii (Liu et al. 2020), shows high variations both morphologically and microscopically from the newly described Indian F. thiruvannamalaiensis.

Fig. 1: Fulvifomes thiruvannamalaiensis (MUBL4013, holotype). a. Habitat, b. Pilear surface, c. Pore surface, d. Stratified layer (yellow arrows and lines indicates each stratum), e. Contextual hyphae, f. Tramal hyphae, g. Cystidioles, h. Basidioles, i. Basidia and j. Basidiospores (ad= 1cm, ej = 10µm).