Sulzbacheromyces arunachalensis A. Debnath and Nayaka 2025, sp. nov.

Sulzbacheromyces arunachalensis A. Debnath and Nayaka, sp. nov. (Fig. 2 and 3) MycoBank.: MB855424 GenBank nrITS.: PQ283976 and PQ284036. Type:— INDIA, Arunachal Pradesh: East Kameng District, Khenewa, 27°36′34.69″N, 93°00′54.17″E, on roadside soil mound, elev. 1133 m, 09-11-2022, S. Nayaka and A. Debnath 22-047565 (LWG-holotype and isotype). Diagnosis:—Basidiomata unbranched, terete to fusiform, aduncate flexed, white to off-white when fresh and hydrated, turning russet brown upon drying. Sterigmata four, basidiospores with a noticeable adaxially concave surface. Description:— Thallus terricolous, forming thin, light to dark green crust, 7–16 cm diam., prothallus absent, photobiont chlorococcoid, 5–11 μm diam., spherical to ellipsoid or slightly angular, smooth, contiguous in groups, wrapped by a single layer of hyaline fungal hyphae, 3–6 μm thick, clamp connections absent. Basidiomata simple, solid, solitary, surface smooth to a little rugulose, glabrous, epruinose, barely flattened sideways, terete to fusiform having an aduncate flexure, rarely straight, 12–16 mm high, 1.5–2 mm diam., white to off white when fresh and hydrated, turning russet brown upon drying, hymenium tissue covering the upper part of the basidiomes. The section of basidiomata composed of two layers; outwards loosely organized, perpendicular basidia resembling hyphae, 20–25 μm high and inwards concentrated, isodiametric, parallel, thin-walled, densely agglutinated hyphal strand lacking clamp connection, 120–140 μm thick. Trama composed of thin-walled, unbranched, tightly adhered, septate, parallel hyphae, 5.6–7.1 μm thick, lacking clamp connection. Globose, oil drop like materials always present in the tissue, 2–7 µm diam. Basidia subclavate to clavate, guttulate with inflated apex, thin walled, hyaline, 21.4–29.6 × 10.4–12.6 µm, with four short sterigmata. Sterigmata thin, slender, 2.5–3.6 × 1.0–1.9 µm, lacking clamp connection. Basidiospores smooth, thin walled, aseptate, hyaline, reniform, inamyloid (7.1–)7.4–8.6(–8.9) × (3.0–)3.4–3.7(–3.9) µm, L = 7.6 µm, W = 3.9 µm, Q = (1.8–)1.9–2.2(–2.3), Qm = 1.94, N = 25, often guttulate with hilar appendix, lacking a basal clamp. Basidioles numerous, resembling sterile basidia, lacking sterigmata, parallelly arranged in the hymenial element, 25.2– 31.4 × 9.4–13.1 µm, thin walled, hyaline, pyriform, apex with vesicle like globose swelling, sometimes guttulate. Hymenial cystidia like elements absent. Chemistry:—Thallus and hymenophore K−, C−, KC−, P−; no substances detected by TLC. Etymology:—The species epithet refers to its type locality Arunachal Pradesh. Distribution and ecology:— Sulzbacheromyces arunachalensis is recorded from East Kameng district of Arunachal Pradesh at an elevation of 1133 m, growing on the moist upright surface of soil mound along roadside. Remarks:— Sulzbacheromyces arunachalensis is characterized by its whitish, curved, terete, unbranched basidiomata 12–16 × 1.5–2 mm; lacking prothallus and clamp connection; clavate basidia 21.4–29.6 × 10.4–12.6 µm, inflated apex, guttulate; sterigmata four and reniform spores 7.1–8.9 × 3.0–3.9 µm. It is close to Asian species S. bicolor phylogenetically by having white basidiomata, however S. bicolor differs by having silvery white prothallus, notably longer, branched, clavarioid or cylindrical bicolored basidiomata (3–23 × 0.3–1 mm), along with the presence of inflated colon like hyphae and clamp connections. Sulzbacheromyces arunachalensis and S. fossicola display white basidiomata, but S. fossicola is clearly distinguished by its clavarioid to cylindrical, once or twice-branched basidiomata from the base. Sulzbacheromyces arunachalensis is similar to Neotropical species S. leucodontius in exhibiting white basidiomata; however, S. leucodontius differs in having significantly longer basidiomata (6–25 × 0.6–0.9 mm) with inflated base, sterigmata two and comparatively smaller ellipsoid basidiospores (3 × 6 µm). With its white basidiomata the new species macro-morphologically also distinguished form S. caatingae (dull orange-pink to dull yellow basidiomata), S. chocoensis (reddish orange to yellowish basidiomata), S. miomboensis (deep orange to reddish orange basidiomata), S. sinensis (yellow, orange to red orange basidiomata), S. tutunendo (reddish orange to yellowish orange basidiomata) and S. yunnanensis (yellow to orange basidiomata). The new species consistently differs from all other species of the genus in having distinct and uniform curved basidiomata when young, regardless of the substrate angle. Detailed comparison of Sulzbacheromyces arunachalensis with other taxa is provided in Table 2.