Tropicoporus natarajaniae M. Kaliyaperumal, S. Gunaseelan, K. Kezo, Xue W. Wang & L.W. Zhou, sp. nov.
Index Fungorum number: IF 559816; Mycobank number: MB 599816; Facesoffungi number: FoF 12715; Figs. 1, 2
Etymology – The species epithet “natarajaniae” referring to the Indian mycologist, Krishnamoorthy Natarajan, for his contributions to the Indian mycology especially on taxonomic studies in Agaricomycetes.
Holotype – MUBL4020.
Diagnosis – Tropicoporus natarajaniae is characterized by velutinate to abundantly tuberculae or warted pilear, uncracked pilear surface, on maturity becoming greyish brown with few cracks only near attachment, obtuse, velutinate margin and stratified tube with mono-dimitic hyphal system, presence of cystidioles and setae with broadly ellipsoid to subglobose basidiospores.
Basidiomes perennial, solitary, pileate, sessile, light in weight, hard when dry. Pileus dimidiate, applanate, with no distinct crust, projecting up to 5.4 cm, 6.6 cm wide and 3.6 cm thick near the attachment. Pilear surface on first pubescent to velutinate, smooth with few tuberculae or warts in young basidiomes, uncracked, azonate, yellowish brown (5E5, 5F8) to brown (6E8), on maturation pilei becoming velutinate with abundant tuberculate or warts on the surface, becoming greyish brown (6F3) with few cracks near attachment. Margin entire, obtuse, yellowish brown (5F8). Pore surface brown (6E6) to dark brown (6F6). Pores round to angular, regular, 5–7 per mm. Dissepiments entire, thick. Context duplex with no blackline, up to 1.5 cm, light brown (6D8) to brown (6E7). Tubes 0.7 cm in length, indistinctly stratified, each stratum up to 3 mm, brown (6E8).
Hyphal system monomitic in the context and dimitic in the tubes, tissue darkening with KOH without swelling. Context generative hyphae, thin to thick walled, hyaline to golden yellow, simple septate, rarely branched, 2–5 μm in diam. Tramal generative hyphae dominant, thin to thick walled, hyaline to pale yellow, septate, occasionally branched, 2–4.8 μm in diam. Skeletal hyphae thick-walled with narrow to wide lumen, yellowish brown, aseptate, unbranched, 2–4.5 μm in diam. Hymenial setae dark brown, thick-walled, ventricose to subulate with a sharp to blunt tips, 6–18.7×4.3–5.3 μm. Cystidia absent. Cystidioles hyaline, thin-walled, ventricose to fusoid with elongated tapering apical portion, 4.8–27×3.8–6 μm. Basidia clavate to subclavate, 6–18×3.8–6.2 μm, with four sterigmata and a simple septum at the base. Basidioles clavate, 4.8–16 × 3.5–6 μm. Basidiospores broadly ellipsoid to subglobose, pale yellow in water, turning golden yellow to brown in KOH, fairly thick walled to thick–walled, smooth, inamyloid, nondextrinoid, acyanophilous, (4.6–) 5–6 (–6.5)×(4.1–) 4.6–4.9 (–5.2) μm (n=50/1), Q=1.1 (Q range 1.05–1.3).
Material examined – India, Tamil Nadu, Thiruvannamalai district, Sathanur, Pennaiyar river, 12º 08′00.34″N, 78º 56′48.63″E, on living angiosperm tree (Albizia amara), 03 Febraury 2018, Sugantha Gunaseelan, MUBL4020 (holotype).
GenBank number – ITS=OP003881.
Notes – Tropicoporus natarajaniae is characterized by pileate basidiomes with a mono-dimitic hyphal system, while other Tropicoporus species such as T. boehmeriae, T. hainanicus, T. minus, T. ravidus, T. stratificans, T. tenuis and T. texanus are reported to be resupinate with a dimitic hyphal system (Wu et al. 2015, 2022a, b; Coelho et al. 2016; Brown et al. 2020). Absence of setae makes T. nullisetus (Lima et al. 2022) distinct from other reported Tropicoporus species.
Figure 1 – Morphological characters of Tropicoporus natarajaniae a Basidiomata (Holotype). b Pore surface. c Cross-section of basidiome with obtuse margin. d Indistinctly stratified tube layer. e Contextual hyphae. f Tramal hyphae. g-h Hymenial setae. i Cystidioles. j Basidia. k Basidioles. l-p Basidiospores: l Basidiospore. m Basidiopore in water. n Basidiopore in KOH. o Basidiopore in cotton blue. p Basidiopore in Melzer’s reagent. Scale bar: e-p = 5 μm
Figure 2 – Phylogram generated by the maximum likelihood algorithm based on combined nLSU and ITS sequence data is presented along with the bootstrap values and the Bayesian posterior probabilities above 50% and 0.8, respectively, at the nodes. Type specimens are in bold and the isolates of new species characterized are in blue