Additions to Hohenbuehelia (Basidiomycota, Pleurotaceae): two new species and notes on H. tristis from northern Thailand Author Phonemany, Monthien https://orcid.org/0000-0002-7865-4659 School of Science, Mae Fah Luang University, Chiang Rai 57100, Thailand Author Vadthanarat, Santhiti https://orcid.org/0000-0002-9035-0375 School of Science, Mae Fah Luang University, Chiang Rai 57100, Thailand & Center of Excellence in Fungal Research, Mae Fah Luang University, 333 M. 1 Thasud, Mueang, Chiang Rai 57100, Thailand Author Raghoonundon, Bhavesh https://orcid.org/0000-0001-6671-2404 School of Science, Mae Fah Luang University, Chiang Rai 57100, Thailand Author Thongklang, Naritsada https://orcid.org/0000-0001-9337-5001 School of Science, Mae Fah Luang University, Chiang Rai 57100, Thailand Author Raspe, Olivier https://orcid.org/0000-0002-8426-2133 School of Science, Mae Fah Luang University, Chiang Rai 57100, Thailand Olivier.Ras@mfu.ac.th text MycoKeys 2023 2023-08-21 99 109 130 http://dx.doi.org/10.3897/mycokeys.99.105317 journal article http://dx.doi.org/10.3897/mycokeys.99.105317 1314-4049-99-109 AC275090D82D57288480E8AD1CDFFFF3 Hohenbuehelia flabelliformis Phonemany & Raspe sp. nov. Figs 2 , 3 Diagnosis. This species is distinguished from other Hohenbuehelia species by large flabelliform basidiomata, yellowish-white pileus that is densely villose with white hairs longer near the point of attachment, and shorter towards the margin, ellipsoid basidiospores, absence of cheilocystidia, and a trichoderm pileipellis. Figure 2. Basidiomata of Hohenbuehelia flabelliformis in the field a, c-e MFLU22-0008 b MFLU22-0009. Scale bars: 1 cm ( a-e ). Holotype. Thailand, Chiang Mai Province, Mae Taeng District, Pha Daeng Village, 27 May 2019, Monthien Phonemany (MFLU22-0008). Figure 3. Micromorphology of Hohenbuehelia flabelliformis (MFLU22-0008, MFLU22-0009) a basidiospores b pleurocystidia c basidia and basidioles d pileipellis. Scale bars: 10 µm ( a, c ); 20 µm ( b, d ). Etymology. " flabelliformis " refers to the flabelliform shape of basidiomata. Description. Pileus 35-45 x 20-40 mm, spathulate when young, expanding to spathuliform, flabelliform, rounded flabelliform or orbicular, white when young, becoming yellowish-white to pale yellow (4A2-4A3) at the centre and cream (2A3-2B3) to slightly darker elsewhere in age; surface densely villose with white hairs that are longer near the attachment and shorter towards the margin, as observed with a lens; margin white, incurved when young, becoming straight when old. Lamellae 1-3 mm wide, decurrent, pale yellow to yellowish-white (4A3-4A2), moderately crowded when mature, with lamellulae in 1-3 tiers; edge concolorous to sides, fimbriate. Stipe absent or as pseudostipe 5-12 mm x 3-8 mm. Context consisting of two layers: 1) non-gelatinous layer, 1 mm thick, soft when young and rather leathery when old, white to dirty white (4A1-4A2); 2) gelatinous layer 0.5 mm thick, soft, sticky, colourless. Odour mild, pleasant. Taste none. Spore print white. Basidiospores [150/3/2] (5.8-)6-7-8(-8.6) x (3.5-)4-4.2-5(-5.1) µm , Q = (1.3-)1.36-1.67-2.01(-2.03), ellipsoid to elongate (oblong) in side view, smooth, thin-walled, inamyloid. Basidia (21-)21-25.8-35(-37) x (5-)5.3-7.3-10.5(-11) µm , subclavate to clavate, with 4 sterigmata 4-8 µm long, hyaline, smooth, thin-walled. Cheilocystidia absent. Pleurocystidia metuloidal, present on both sides of lamellae and visible with a lens, (34-)34-42-54(-55) x (8.5-)8.5-11-14(-14.5) µm , scattered, narrowly fusiform to fusiform, mucronate at apex, brownish in KOH. Hymenophoral trama irregular, hyphae 2-5 µm wide. Pileipellis a trichoderm, hyaline in KOH, brownish in water, with cylindrical terminal elements 34-86 x 4-7 µm . Pileoleptocystidia absent. Pileus trama consists of two different layers: 1) upper layer gelatinous, composed of horizontally arranged, smooth, colourless encrusted hyphae, 2-5 µm wide; 2) lower layer, non-gelatinous, composed of interwoven, smooth, hyaline hyphae, 2-4 µm wide. Clamp connections present in pileipellis, pileus trama, and hymenophoral trama. Habitat and distribution. On dead wood, scattered or fasciculate by 2-4 basidiomata. So far only found in tropical forests of northern Thailand. Additional specimens examined. Thailand . Chiang Rai Province , Pa Daed District , Pa Ngae Village , 9 August 2019 , Monthien Phonemany (MFLU22-0009) . Notes. The basidiomata colour of Hohenbuehelia flabelliformis is similar to H. angustata (Berk.) Singer, H. bonii A.M. Ainsw., H. concentrica Corner, H. carlothornii Consiglio, Setti & Thorn, H. horrida (Boedijn) Corner, H. luteola G. Stev, H. malesiana Corner, H. odorata C.K. Pradeep & Bijeesh, H. olivacea Yu Liu & T. Bau, and H. testudo (Berk.) Pegler. The basidiomata range from white, yellowish-white, yellow-brown, to pinkish-orange, and are spathulate to flabelliform. Hohenbuehelia angustata , originally described from Brazil, differs from H. flabelliformis by its smaller, smooth, greyish-yellow basidiomata, with stipe 4.5 mm long, smaller basidiospores (3.5-5 x 2.5-3.5 µm ), smaller cheilocystidia, and the presence of pileocystidia ( Silva-Filho and Cortez 2017 ). H. horrida and H. odorata differ from H. flabelliformis by smaller basidiospores (5.2-7.6 x 4.8-6.4 µm ), lack of cheilocystidia, and presence of pileoleptocystidia ( Bijeesh et al. 2019 ). Hohenbuehelia testudo differs by smaller basidia (20-25 x 5-6 µm ), larger pleurocystidia (44-78 x 12-18 µm ) with thick yellowish walls, and the presence of cheilocystidia ( Corner 1994 ). Hohenbuehelia malesiana , described from Brazil, is different from H. flabelliformis by having longer, subcylindrical basidiospores (7-9 x 3.5-4 µm ), pileipellis as an interrupted cutis, and presence of cheilocystidia ( Corner 1994 ). Hohenbuehelia bonii , from England, has larger yellow-brown basidiomata (20-75 mm diam.), smooth pileus surface, larger basidiospores (7.2-10.4 x 4.5-6.1 µm ), larger pleurocystidia (56-103 x 11-19 µm ), and an ixotrichoderm or ixocutis pileipellis ( Ainsworth et al. 2016 ). Hohenbuehelia carlothornii described from Costa Rica, is different by having off-white basidiomata with a large pseudostipe (20-32 x 14-25 mm), presence of cheilocystidia ( Consiglio et al. 2018b ). Hohenbuehelia concentrica from Singapore, has larger basidiomata (80 mm wide), larger basidiospores (8-8.5 x 6-6.7 µm ), and absence of cheilocystidia ( Corner 1994 ). Hohenbuehelia incarnata , from the Solomon Islands, differs from H. flabelliformis by subglobose basidiospores and the presence of subcylindrical to submoniliform cheilocystidia ( Corner 1994 ). Hohenbuehelia olivacea , originally described from China, has reniform basidiomata with dense and long tomentum, light brown to pallid brown in gelatinous zone, and the presence of cheilocystidia ( Liu and Bau 2009 ). Phylogenetically, H. flabelliformis was closely related to H. algonquinensis Consiglio, Setti & Thorn. (voucher RGT 870601/12 UWO) with 3.5% (21/599) differences in the ITS sequence, 1.4% (12/839) in the LSU sequence, and 6.66% (35/540) in the tef 1 sequence. Moreover, the morphologies of both species are completely different, with H. algonquinensis having glossy black pileus, ungulate to dimidiate basidiomata and contrasting white or off-white lamellae ( Consiglio et al. 2018b ).