Hymenagaricus wadijarzeezicus Al-Sadi, Al-Yahya'ei , A. Al-Owaisi & S. Hussain, 2024

Hussain, Shah, Al-Kharousi, Moza, Al-Maqbali, Dua'a, Al-Owaisi, Arwa A., Velazhahan, Rethinasamy, Al-Yahya'ei, Mohamed N. & Al-Sadi, Abdullah M., 2024, Two new species of Hymenagaricus (Agaricales, Agaricaceae) from Oman, based on morphology and molecular phylogeny, MycoKeys 105, pp. 1-19 : 1

Hymenagaricus wadijarzeezicus Al-Sadi, Al-Yahya'ei, A. Al-Owaisi & S. Hussain sp. nov.

Figs 2 , 3 , 4

Diagnosis.

The new species Hymenagaricus wadijarzeezicus can be differentiated from other species of the genus by its unique whitish woolly veil, covering both the cap and the stipe surfaces.

Holotype.

Sultanate of Oman: Dhofar, Salalah, Wadi Jarzeez, on termite mounds, under the trees of Anogeissus dhofarica , 11 August 2022, S. Hussain, A. Al-Owaisi & Al-Yahya’ei, JRZ2-22-013 (holotype Mawarid-JRZ2-22-013), GenBank accession: ITS = OR612999, 28S = OR613019, EF-1α = OR729599.

Etymology.

The specific epithet ' wadijarzeezicus ' refers to the valley Jarzeez in the south of Oman, where the holotype was found.

Description.

Basidiomata small to medium-sized. Pileus 30-80 mm in diam., at the young stage, broadly ovoid to parabolic, covered completely by a smooth, pale brownish pellicle; at mature stage, pulvinate to convex, pellicle disrupting except at the centre where it is retained as one large, smooth, brownish squamule, surface is woolly, covered with whitish, strigose to villose or floccose veil towards the margin; margin appendiculate with long, whitish, fibrils of veil. Context dark pinkish on cutting, 3-5 mm thick at the pileus centre. Lamellae free, pale pinkish at young stage, at mature stage greyish-pink to brownish, ventricose, up to 3 mm wide, densely crowded, with 1-3 series of lamellulae. Stipe 30-60 × 5-10 mm, equal, with a slightly bulbous base, with root-like rhizoid structure at the base, annulus floccose, concolorous to veil; stem covered with floccose veil below the annulus, smooth above the annulus, context pinkish on cutting, fistulose. Smell pleasant. Taste not recovered.

Basidiospores (6.5)7.0-8.0(8.5) × (4.0)4.5-5.5(6.0) µm, average size 7.5 × 5.0 µm, Q = 1.4-1.6, av. Q = 1.5; ellipsoid to broadly ellipsoid, yellowish to dark brown, smooth, thick-walled, apiculus visible, germ-pore not observed. Basidia 20-25 × 7-9 µm, on average 22.5 × 8.0 µm, clavate to cylindrical, smooth, hyaline in KOH, mostly tetrasporic, rarely bisporic. Cheilocystidia 16-23 × 7-9 µm, on average 19.5 × 8.0 µm, ellipsoid to subclavate, smooth, thin-walled, hyaline in KOH. Pleurocystidia absent. Lamellar trama regular, with 4-6.6 µm diam., cylindrical to inflated, thin-walled, hyaline hyphae. Subhymenium consisted of subglobse to irregular cells, measuring 12-18 µm diam. Pellicle is a hymeniform, consisting of chains of two or three elements, measuring 13-17 × 10-16 µm each element, globose to subglobose or ovoid, hyaline, or pale yellowish, smooth, thin-walled, these chains of elements attached to inflated hyphae with encrusted walls. Pileus veil is a cutis to ixocutis, consisting of elongated or cylindrical elements, easily detached, hyaline, thin-walled, each element measuring 13-45 × 6-9 µm. Annulus is an intricate trichoderm, composed of hyaline hyphae, 6-8 µm diam., cylindrical, constituted by short elements, constricted at septa, easily disarticulated. Stipe veil similar to pileus veil. Clamp connections absent in all tissues.

Habit, habitat, and distribution.

Occurring in July to early September, as saprotrophic, solitary or scattered in small groups, on or near the termite mounds, under the trees of Anogeissus dhofarica . Currently only known from southern Oman.

Additional specimens examined.

Sultanate of Oman: Dhofar, Salalah, Wadi Naheez, on termite mounds, under the trees of Anogeissus dhofarica , 07 August 2022, S. Hussain, A. Al-Owaisi, Al-Yahya’ei & Al-Sadi, NHZ-22-019 (Mawarid-NHZ-22-019), GenBank accession: ITS = OR612997, 28S = OR613020, EF-1α = OR729602; Wadi Jarzeez , under the trees of Anogeissus dhofarica , 08 August 2022, S. Hussain, A. Al-Owaisi, Al-Yahya’ei & Al-Sadi, JRZ-22-005 (Mawarid-JRZ-22-005), GenBank accession: ITS = OR612996, 28S = OR613022, EF-1α = OR729603; Wadi Jaheen , under the trees of Anogeissus dhofarica , 10 August 2022, S. Hussain, A. Al-Owaisi, Al-Yahya’ei & Al-Sadi, JHN-22-019 (Mawarid-JHN-22-019), GenBank accession: ITS = OR612998, 28S = OR613021, EF-1α = OR729600; Wadi Jarzeez , on termite mounds, under the trees of Anogeissus dhofarica , 11 August 2022, S. Hussain, A. Al-Owaisi & Al-Yahya’ei, JRZ2-22-015 (Mawarid-JRZ2-22-015), GenBank accession: ITS = OR613000, 28S = OR613018, EF-1α = OR729601; Wadi Gogob , on termite mounds, under the trees of Anogeissus dhofarica , 22 August 2023, S. Hussain & Al-Yahya’ei, GOB-23-008 (Mawarid-GOB-23-008); Sahalanawt, on termite mounds, 27 August 2023, S. Hussain & Muhammad Salim, Sahalanawt-23-001 (Mawarid-Sahalanawt-23-001); Tetam, on termite mounds, 30 August 2023, S. Hussain & Amer Qattan, Tetam-23-001 (Mawarid-Tetam-23-001) .

Notes.

The new species Hymenagaricus wadijarzeezicus with medium-sized basidiomata, can be distinguished from the known species of the genus by its remarkable woolly cap and stipe surfaces. In Hymenagaricus , there are four species with a cap diameter of 50 mm or above, which are: Hymenagaricus cf. kivuensis , H. mlimaniensis Mwanga & Tibuhwa, H. ardosiaecolor and H. alphitochrous (Berk & Broome) Heinem. Hymenagaricus wadijarzeezicus is the 5th species with a cap diameter above 50 mm. None of these species has a woolly basidiomata surface, except Hymenagaricus wadijarzeezicus .

In ML phylogeny, the most similar species to the new species H. wadijarzeezicus is H. saisamornae . Hymenagaricus saisamornae is a recently described species from Thailand, with substantially smaller basidiomata (10-25 mm cap diam.), pileus surface covered with minute brownish squamules, stipe smooth to finely whitish squamulose and smaller basidiospores (5.5-7.0 × 4.0-4.5 µm; Kumla et al. (2021)). Similarly, Hymenagaricus cf. kivuensis and H. mlimaniensis , both African species, shared medium-sized pileus with H. wadijarzeezicus . Hymenagaricus cf. kivuensis has pileus of 50-100 diam., with smaller basidiospores (4.0-6.5 × 3.0-4.5 µm), narrower basidia (16-20 × 4.5-6) and broader hymeniform cells ( Pegler 1977; Heinemann 1984). Hymenagaricus mlimaniensis has a broadly umbonate, reddish-brown disc, with sparsely squamulose surface and smaller basidiospores (4.0-7.0 × 3.5-4.5 µm; Mwanga and Tibuhwa (2014)) than H. wadijarzeezicus (7.0-8.0 × 4.5-5.5 µm). Hymenagaricus siamensis differs from H. wadijarzeezicus by its smaller basidiomata with brownish cap, measuring 22-32 mm diam., squamules consisting of pseudoparenchymatous cells ( Kumla et al. 2023). Another small-sized species Hymenagaricus pakistanicus with pileus 24-30 mm diam., covered with dark brownish squamules at the cap centre, smaller basidiospores (5.0-6.0 × 3.5-5.0 µm) and a pseudoparenchymatous pellicle ( Syed et al. 2023).

Figures

Figure 2. Basidiomata of Hymenagaricus wadijarzeezicus A-C holotype collection (JRZ 2 - 22 - 013) D, E NHZ- 22 - 019 F young fruiting bodies where the cap is entirely covered by pellicle represented by arrows (JRZ 2 - 22 - 015) G context changed into pinkish on cutting, the arrow represents the root-like rhizoid (JRZ 2 - 22 - 015). Scale bars: 20 mm.

Figure 3. Light microscopy of anatomical features of Hymenagaricus wadijarzeezicus (based on holotype collection JRZ 2 - 22 - 013) A basidiospores B, C basidia D cheilocystidia E annulus F veil elements G pellicle structure. Scale bars: 10 µm (A); 15 µm (B-D); 15 µm (E-G).

Figure 4. Line drawings of anatomical features of Hymenagaricus wadijarzeezicus (based on holotype collection JRZ 2 - 22 - 013) A basidiospores B basidia C cheilocystidia D pellicle structure E annulus F veil elements. Scale bars: 10 µm (A); 15 µm (B-D); 15 µm (E, F).