Lentinus saisamorniae Kumla & N. Suwannar., 2025

Kumla, Jaturong, Kaewnunta, Atsadawut & Suwannarach, Nakarin, 2025, Lentinus saisamorniae (Polyporaceae, Polyporales), a new edible macrofungus from northern Thailand, Phytotaxa 705 (2), pp. 149-161 : 154-156

Lentinus saisamorniae Kumla & N. Suwannar. sp. nov. Figures 2 and 3 .

MycoBank number: MB 857966

Diagnosis:—Distinguishable from the close relative L. cladopus by its smaller basidiospores and longer basidia.

Etymology:— ‘ saisamorniae ’ refers to Emeritus Prof. Dr. Saisamorn Lumyong in honor of her 75 th birthday and over 35 years of contribution to Thai mycology.

Holotype:— THAILAND. Chiang Mai Province, Mueang Chiang Mai District, Chiang Mai University , 18°48’13”N 98°57’21”E, elevation 334 m, on decaying wood in a tropical deciduous forest, 8 August 2019, J. Kumla & N. Suwannarach, CMUB40076 .

Gene sequences (from holotype):—PV244426(ITS), PV241809 (nrLSU), and PV252128 (rpb1)

Description:— Basidiomata small to medium-sized. Pileus 10–85 mm in diameter, convex to applanate, deeply depressed at center or infundibuliform shaped, with concentrically fibrillose squamules crowded at center toward margin, white (4A1) to yellowish-white (3A2–4A2), margin smooth or broken when mature, with white fibrillose. Lamellae decurrent, white (4A1), narrowed, up to 2 mm wide, with white (4A1) smooth margin. Stipe central to lateral, 20–90 × 2.5–10 mm, cylindrical, equal or slightly tapering to base, white (3A1) to yellowish-white (3A2), smooth or with white (3A1) to yellowish-white (3A2–4A2) fibrillose. Annulus absent. Context white (4A1) at pileus and stipe, fleshy-tough to leathery, consisting of a dimitic hyphal system with generative and skeletal hyphae. Generative hyphae 2.0–5.5 μm in diameter, hyaline, thin-walled, frequently branching, with clamp connections. Skeletal hyphae 2.5–10.0 μm wide, hyaline, thick-walled, unbranched or with an occasional lateral branched. Spore print white.

Basidiospores [150/10/4] (4.5)5.1–5.6(6.5) × (3.0)3.2–3.8(4.0) μm, Q = 1.38–1.83, Q m = 1.60±0.12, broadly ellipsoid to ellipsoid, occasionally elongate, thin-walled, smooth, hyaline, inamyloid. Basidia 18.0–27.5 × 4.5–7.0 μm, clavate, thin–walled, hyaline, 4-spored, sterigmata up to 5.0 μm long. Pleurocystidia absent. Hyphal pegs abundant, extending up to 50 μm in diameter, consisting of thin-walled, cylindric hyphae, hyaline, 1.0–3.0 μm in diameter. Cheilocystidia 15.0–45.0 × 3.0–6.0 μm, narrowly clavate to clavate or narrowly cylindrical to cylindrical, hyaline, thin-walled. Hymenophoral trama hyaline, irregular and intermixed, similar to the context. Pileipellis cutis, trichoderm, cylindric, terminal elements with obtuse apices, sometimes with a narrowed or slightly strangulated apex, up to 50 μm long, a dimitic hyphal system; generative hyphae 2.0–4.5 μm in diameter, hyaline, thin-walled, branched, with clamp connections; skeletal hyphae 2.5–10.0 μm in diameter, hyaline, unbranched or with an occasional lateral branched, thick-walled. Stipitipellis cutis, similar to the pileipellis in composition but the terminal elements often tend to form small , loose aggregations. Clamp connections abundant at all tissues.

Ecology and distribution:—Fruiting solitary or gregarious on decaying wood and soil in a tropical deciduous forest. Known only from the type locality in northern Thailand.

Additional specimens examined:— THAILAND, Chiang Mai Province, Mueang Chiang Mai District, Chiang Mai University , 18°48’13”N 98°57’21”E, elevation 334 m, on soil in a tropical deciduous forest, 3 July 2020, J. Kumla & N. Suwannarach, SDBR-CMUNK0795, 18°48’20”N 98°57’25”E, elevation 335 m, on decaying wood in a tropical deciduous forest, 17 July 2021, J. Kumla & N. Suwannarach, SDBR-CMUNK1515 ; Doi Saket District, 18°53’2”N 99°9’17”E, elevation 343 m, local market, 26 July 2021, Kumla J. and Suwannarach N., SDBR-CMUNK0837 .

Note:—Morphologically, L. saisamorniae resembles L. cladopus , L. concavus (Berk.) Corner , and L. squarrosulus in terms of pileus color. However, the larger basidiospores (6.5–8.5 × 3.7–4.7 μm) and shorter basidia (15.0–17.5 × 4.0–4.5 μm) in L. cladopus distinguish it from L. saisamorniae ( Berkeley 1852, Singer 1956, Pegler 1977). Notably, the presence of the longer basidiospores in L. concavus (5.5–8.0 × 2.0–4.0 μm) clearly differs it from L. saisamorniae , and L. concavus is only found in South America ( Berkeley 1852; Singer 1956, Pegler 1977, 1983, Minter et al. 2001, Franco-Molano et al. 2005, Vasco-Palacios et al. 2005, Bononi et al. 2008, Gates et al. 2021, Angelini 2022). The longer and narrower size of basidiospores (5.0–8.0 × 1.5–3.0 μm) in L. squarrosulus make it different from L. saisamorniae ( Corner 1981, Pegler 1977, 1986, Sysouphanthong et al. 2023). Phylogenetically, L. saisamorniae formed a monophyletic clade sister to L. cladopus . The ITS sequences of L. saisamorniae showed similarity values ranging from 79.90% to 80.20% when compared to the ITS sequences of L. cladopus VKMK 05 and S3004. Moreover, a pairwise nucleotide comparison of ITS data indicated that L. saisamorniae differed from L. cladopus VKMK 05 and S3004 by 20.75% (137/660 bp including gap) and 21.06% (139/600 bp including gap), respectively.

Figures

FIGURE 2. Basidiomata of Lentinus saisamorniae. A. (CMUB40076, holotype) and B. SDBR-CMUNK0795. Scale bars: A = 25 mm and B = 50 mm.

FIGURE 3. Microscopic structures of Lentinus saisamorniae (CMUB40076, holotype). A. Basidiospores; B Basidia; C. Cheilocystidia; D. Generative hyphae; and E. Skeleton hyphae. Scale bars: A‒E = 5 μm.