Hemileccinum inferius Vadthanarat, Raghoonundon & Raspe, 2024

Vadthanarat, Santhiti, Raghoonundon, Bhavesh, Lumyong, Saisamorn & Raspe, Olivier, 2024, Rostrupomyces, a new genus to accommodate Xerocomus sisongkhramensis, and a new Hemileccinum species (Xerocomoideae, Boletaceae) from Thailand, MycoKeys 103, pp. 129-165 : 129

Hemileccinum inferius Vadthanarat, Raghoonundon & Raspe sp. nov.

Figs 6 , 7

Etymology.

" Hemileccinum inferius " refers to the only lower part of the stipe ornamented with reticulum

Holotype.

Thailand, Chiang Mai Province, Muang District, Doi Suthep-Pui National Park, 18°47'52.8"N, 98°54'21.2"E, elev. 1,170 m, 1 July 2016, Santhiti Vadthanarat, SV0282 (holotype: CMUB, isotype: BKF, MFUB). ITS sequence accession number PP354892.

Diagnosis.

Hemileccinum inferius can be differentiated from resembling Hemileccinum species by a grayish red to reddish brown to dark brown, plane to sub-depressed, subrugulose to pitted pileus; and yellow to yellowish white, cylindrical with subbulbous stipe, with surface even on the upper half and subscabrous to delicately reticulate on the lower half, as well as smooth basidiospores even when observed under SEM.

Description.

Basidiomata medium-sized. Pileus 66-68 mm in diameter, plane to sub-depressed at the centre; margin deflexed in age, elastic, slightly exceeding (up to 1 mm); surface subrugulose to pitted especially near the margin, dull, moist to slippery when wet, tomentose, grayish red (8B/C3-4) to reddish brown (8D/E4-6) to dark brown to reddish brown (7-8F4-6), unchanging when bruised; context 8-10 mm thick haft-way to the margin, firm to soft, pale yellow (1A3), slightly brown (7E5) near the pileus surface, light yellow (1A4) above the hymenium in age, unchanging when cut. Stipe 65-76 × 14-18 mm, central, terete, cylindrical with subbulbous base; surface even on the upper half then subscabrous to delicately reticulate on the lower half, dull, dry to moist, light yellow (2A4-6) to yellowish white to pale yellow (2A2-3) at the base, occasionally with reddish brown to dark brown spots (8D5-8, 8F7) at places, minutely covered with pale yellow to light brown to dark brown (2A3-4 to 7D/E4, 7F8) squamules on the upper half, slightly fibrillose following a reticulate pattern at the middle of the stipe getting less so to the base, unchanging when bruised; basal mycelium white (1A1); context solid, firm, pale yellow (2A3-5) especially in the above half near the stipe surface becoming yellowish white (2A2) to off-white at the base, unchanging when cut. Hymenophore tubulate, slightly depressed around the stipe, with slightly decurrent tooth, subventricose. Tubes 7-8 mm long half-way to the margin, yellow to grayish yellow (2A7 to 2B7) near the pileus context then olive (2E5) near the pores, separable from the pileus context, unchanging when bruised. Pores 0.3-0.8(1.2) mm wide at mid-radius, subangular to angular, even, grayish yellow (2B5), unchanging when touched, irregularly arranged; topography subregular. Odour mild fungoid. Taste mild. Spore print olive brown (4E7).

Macrochemical reactions: KOH, brownish orange on pileus and hymenophore, pale orange on pileus context and stipe surface, and stipe context; NH4OH, brownish orange with purple aura on pileus, yellowish to brownish orange with purple aura on stipe surface, yellowish to greenish or slightly blue on pileus context and stipe context.

Spores [118/2/2] (10.5-)11.4-12.9-14.6(-15.3) × (3.8-)4.2-4.8-5.6(-6.1) µm Q = (2.06-)2.4-2.68-3.05(-3.32). From the type (10.8-)11.5-12.7-14.2(-14.5) × (4.1-)4.3-4.8-5.5(-6.1) µm, Q = (2.06-)2.33-2.66-3.06(-3.1), N = 68, narrowly ellipsoid to subcylindrical with a slight suprahilar depression, thin-walled, smooth under light microscope and SEM (Fig. 5C-D ), yellowish to brownish hyaline in water, yellowish hyaline in KOH, inamyloid. Basidia 4-spored, (23-)24-27-31(-32) × (11-)11-12-14(-14) µm, clavate without basal clamp connection, hyaline to yellowish hyaline in KOH; sterigmata up to 4 µm long. Cheilocystidia (30-)34-54-72(-72) × (7-)8-10-14(-14) µm, narrowly fusiform with elongated obtuse apex, frequent, thin-walled, hyaline to yellowish hyaline in KOH. Pleurocystidia (34-)34-51-69(-70) × (10-)10-11-13(-13) µm, frequent near the pores, narrowly fusiform with elongated obtuse apex, thin-walled, hyaline to yellowish hyaline in KOH. Hymenophoral trama slightly divergent, 62-150 µm wide composed of cylindrical, 4-12 µm wide hyphae, with subregular mediostratum 30-100 µm wide, hyaline in KOH. Pileipellis a hyphoepithelium, 80-112 μm thick, the pileipellis composed of ellipsoid to broadly ellipsoid or cylindrical, thin-walled, more or less vertically arranged, occasionally branching or anastomosing, with metablematic, elongated-cylindrical hyphae (2-4 µm wide hyphae), branching or anastomosing at places, hyaline to yellowish hyaline in KOH; terminal cells of 2 types: 1) ellipsoid to broadly ellipsoid, 8-15 × 12-20 µm; and 2) clavate to broadly clavate with obtuse apex, 10-20 × 4-7 µm. Pileus context made of moderately interwoven, ellipsoid to broadly ellipsoid, thin-walled hyphae, 10-23 µm wide, hyaline in KOH. Stipitipellis arranged parallel to the surface of the stipe (40-50 µm thick), composed of moderately interwoven, cylindrical, thin-walled, 2.5-4 µm wide hyphae, anastomosing at places, moderately scattered with groups of rising cells to clusters (50-60 µm high) of thin-walled clavate to broadly clavate cells (20-30 × 10-15 µm), hyaline to yellowish hyaline in KOH. Caulocystidia not seen. Stipe context composed of parallel, 8-22 µm wide hyphae, hyaline in KOH. Clamp connections not seen in any tissue.

Habitat and distribution.

Solitary, on loamy soil in hill evergreen forest dominated by Fagaceae scattered with a few Dipterocarpus obtusifolius , at 985-1,170 m elevation. Currently known from Chiang Mai Province, northern Thailand.

Additional specimens examined.

Thailand, Chiang Mai Province, Mae Taeng District , 19°06'59"N, 98°44'23"E, elev. 985 m, 6 June 2021, Bhavesh Raghoonundon, BR 0260 (MFLU) .

Notes.

Hemileccinum inferius is described based on collections from Thailand. The comparison of the new species with the seven known Asian species follows. Hemileccinum albidum differs from H. inferius by gray-brown to chrome yellow to ochraceous or golden brown pileus; longer and slender stipe (up to 160 mm); shorter basidiospores (10-12.5 × 4.0-5.5 µm); occurrence at higher elevations (1,968-2,490 m; Li et al. 2021). Hemileccinum brevisporum is similar in pileus color but has shorter basidiospores (9-11 × 4-5 μm); and it occurs under Fagaceae and Pinaceae , at higher elevations (1,700-2,120 m); Li et al. 2021). Hemileccinum duriusculum is macromorphologically quite similar, but differs by a strongly venose pileus surface, even when young, the absence of reticulum on the lower half of the stipe, as well as shorter cheilo- and pleurocystidia ( Liu et al. 2024). Hemileccinum ferrugineipes has similar pileus surface and color but can be differentiated by the apparent pale red-brown color on the lower part of the stipe; and shorter basidiospores (11.0-12.5 × 4-5 μm; Li et al. 2021). Hemileccinum indecorum is clearly different in having dark red to reddish brown basidiomata with mucilaginous surface densely covered with whitish to dirty white, small conical to subconical to irregularly shaped squamules; incurved margin; and yellowish hymenophore that slowly turns brownish to reddish brown when bruised ( Horak 2011; Zeng et al. 2012). Hemileccinum parvum has smaller basidiomata (pileus 3.3-3.6 cm diam, stipe 60-97 × 4-9 mm); paler pileus (brownish to yellowish); pale yellow context that slowly turns pale blue when cut ( Li et al. 2021). Hemileccinum rugosum has paler pileus (light orange to reddish orange); very distinctly rugose to wrinkled pileus surface; and shorter basidiospores (9-13 × 4-5 µm; Wu et al. 2016).

Hemileccinum inferius is also similar to an American species, H. floridanum , which has reddish brown to chestnut brown wrinkled and uneven pileus, whitish to pale yellow stipe, white basal mycelium, yellow hymenophore, and smooth basidiospore under both light microscope and SEM. However, the latter species is different by white context that slowly turns yellow often from the margin toward the center, longer basidiospores (10-17 × 4.5-6 μm), likely forms association with oak in northern America ( Farid et al. 2021).

Phylogenetically, H. inferius was most closely related to H. hortonii , H. rugosum , and an undescribed specimen (voucher HKAS 53421) from China. Hemileccinum hortonii , an American species, can easily be distinguished by its conspicuously pitted pileus, smooth to lightly pruinose stipe that sometimes has delicate reticulation on the upper half, pores that occasionally turn blue on when touched, and slightly longer and narrower basidiospores (12-15 × 3.5-4.5; Kuo and Ortiz-Santana 2020; Farid et al. 2021). For morphological comparison with H. rugosum see the above paragraph.

Figures

Figure 5. Scanning electron micrographs of basidiospores A-B Rostrupomyces sisongkhramensis (SV 0155) C-D Hemileccinum inferius (SV 0282).

Figure 6. Fresh basidioma of Hemileccinum inferius A, B SV 0282 (holotype). Scale bars: 1 cm (A, B).

Figure 7. Microscopic features of Hemileccinum inferius A basidiospores B basidia C cheilocystidia D pleurocystidia E pileipellis F stipitipellis showing a cluster of clavate to boardy clavate like cells which moderately scattered on the stipitipellis. Scale bars: 10 µm (A-D); 25 µm (D-E); 50 µm (E-F). All drawings were made from holotype type (SV 0282).