Two new species of Hymenagaricus (Agaricales, Agaricaceae) from Oman, based on morphology and molecular phylogeny

Hymenagaricus has small to medium-sized mushrooms and the cap surface with squamulose pellicles, consisting of hymeniform or pseudoparenchymatous cells and yellowish-brown basidiospores. The species of Hymenagaricus are very similar to those of Xanthagaricus and it is extremely difficult to differentiate the species of both genera in the field. However, phylogenetically, both the genera are clearly distinct. In this study, we describe two new species of Hymenagaricus, i.e. H. wadijarzeezicus and H. parvulus from the southern part of Oman. Species descriptions are based on a combination of morphological characteristics of basidiomata and phylogenetic analyses of three gene regions: internal transcribed spacer (ITS1-5.8S-ITS2 = ITS), the large subunit of nuclear ribosomal DNA (28S) and translation elongation factor one alpha (EF-1α). Full descriptions, micrographs and illustration of anatomical features, basidiomata photos and phylogenetic analyses results of the new taxa are provided. Morphological comparisons of new taxa with similar species and a key to species included in the phylogenetic analyses are also provided

Micropsalliota ventricocystidiata Al-Sadi & S. Hussain 2022, sp. nov.

Micropsalliota ventricocystidiata Al-Sadi & S. Hussain, sp. nov. (Figs. 3, 4) MycoBank no: MB842602 Diagnosis: Micropsalliota ventricocystidiata can be distinguished from other species by its: medium-sized basidiomata with hemispheric pileus, covered with reddish-brown squamules, basidiospores amygdaliform to oblong, measuring 7.5–8.5 × 4.5–5.0 µm, with ventricose cheilocystidia. Etymology: The specific epithet “ ventricocystidiata ” refers to the ventricose shape of the cheilocystidia of the new species. Type: Oman, Dhofar, Gogob, 17°18′28.9″ N and 54°06′27.6″ E under the trees of Anogeissus dhofarica, 2 Sept 2018, N. Al Dhanki, S. Al Salami, M. Al Jahwari and I. Al Sabahi, GOB-002 (holotype SQUH-GOB002; GenBank accession: ITS = OM 397374, 28 S = OM 630413). Description:Pileus 30–55 mm diam, at young stage ovoid to parabolic, as the pileus opened becoming hemispheric, at mature stage convex to plano-convex; surface finely squamulose, squamules more or less triangular or granular, slightly erect, concentrated at the center, sparse towards the margin, light reddish-brown (2.5YR 5/4–2.5YR 6/4) to moderate reddish-brown (7.5R 3/4–7.5R 3/6) on a white background; margins slightly scalloped. Lamellae free, crowded (25–30 per centimeter), ventricose, reddish-gray (7.5YR 6/2), with 1–5 series of lamellulae, becoming lightbrown (5YR 6/4) with age. Stipe 40–70 × 7–10 mm, central, equal, hollow, surface granulose, granules white, sparce above the annulus, more concentrated below the annulus, on a white background; annulus single layered, membranous, ascendant, white, smooth on both surfaces. Context white, unchanged on handling. KOH reaction reddish-brown on pileus. Odor and taste not recorded. Basidiospores [60/2/2] (7.0)7.5–8.5(9.0) × (4.0)4.5–5.0(5.5) µm, on average 8.2 × 4.8 µm, Q = 1.6–1.86, av. Q = 1.7, ellipsoid to amygdaliform with acute apex in side view, oblong to sub-cylindrical in frontal view, smooth, brownish in 5% KOH, germ-pore absent. Basidia 20–26 × 8–9.5 µm, clavate, hyaline, smooth, 4-spored. Cheilocystidia 36–46 × 9.5–16 µm, mostly ventricose, rarely sub-cylindrical, abundant, smooth, hyaline. Pleurocystidia absent. Pileus covering is a cutis with septate hyphae, 10–15 µm diam, rarely branched, terminal cells 51–67 × 10–12 µm with acute apex, pale brownish in KOH. Clamp connections absent. ......continued on the next page Habitat and distribution: Scattered in small groups, saprotrophic, on humus rich soil with dead leaves and wood under the trees of Anogeissus dhofarica. So far only known from southern Oman. Additional specimens examined: Oman, Dhofar, Attir, on a shady place with plenty of liverworts, 5 Sept 2018, N. Al Dhanki, S. Al Salami, M. Al Jahwari and I. Al Sabahi, ATR-004 (SQUH-ATR004; GenBank accession: ITS = OM 397373, 28 S = OM 630414). Notes: The new species Micropsalliota ventricocystidiata is characterized by a medium-sized basidiomata with hemispheric to plano-convex pileus, covered with reddish-brown squamules; basidiospores amygdaliform with obtuse apex in side view, oblong in face view, measuring 7.5–8.5 × 4.5–5.0 µm and the cheilocystidia mostly ventricose, rarely more or less subcylindrical. ML phylogenetic analyses revealed that the closely related species of M. ventricocystidiata are: M. suthepensis, M. megaspora, M. repanda and M. sp. (SDJ 2021-8-9) an undescribed species from China. Micropsalliota suthepensis, described from Thailand, differs from M. ventricocystidiata by (i) its smaller pileus (10–20 mm diam) with violet squamules (ii) smaller spores (5–6 × 3–3.5 µm) that are somewhat similar in shape and have apical thickening, and (iii) cheilocystidia clavate with non-capitate apex (Zhao et al. 2010). Micropsalliota megaspora, also described from Thailand, differs in its small sized basidiomata, smaller spores (5.2–6.5 × 3.4–4 µm) and pyriform shaped cheilocystidia (Zhao et al. 2010). Micropsalliota repanda, originally described from Togo, differs from the new species by its pinkish pileal fibrils with clavate cheilocystidia (Heinemann 1980). Morphological comparison of the new species with regards to other species of Micropsalliota are further sorted in detail in Table 2. Morphologically, the new species M. ventricocystidiata is similar to M. digitatocystis R.L. Zhao, J.X. Li & M.Q. He (2021: 171), a recently described species from China (Li et al. 2021). Both species share the reddish-brown pileal squamules. On the basis of basidiospores morphology, both species can be differentiated. Basidiospores in M. digitatocystis are mostly ellipsoid to amygdaliform and comparatively smaller (5.8–7.4 × 4–4.6 µm; Li et al. 2021). In M. ventricocystidiata, basidiospores are amygdaliform with obtuse apex to sub cylindrical or oblong and larger (7.5–8.5 × 4.5–5.0 µm). In M. digitatocystis cheilocystidia are cylindrical to subclavate, subcapitate to capitate, measuring 37.4–52 × 9–16.4 µm. On the other hand, cheilocystidia in M. ventricocystidiata are mostly ventricose, rarely subcylindrical.Published as part of Al-Kharousi, Moza, Hussain, Shah, Al-Muharabi, Marwa A., Al-Maqbali, Dua'A, Al-Shabibi, Zahra, Al-Balushi, Abdullah H., Al-Yahya'Ei, Mohamed N., Saady, Nadiya Al, Velazhahan, Rethinasamy & Al-Sadi, Abdullah M., 2022, Notes on the genus Micropsalliota (Agaricales, Basidiomycota) and the description of a new species from Southern Oman, pp. 113-126 in Phytotaxa 543 (2) on pages 119-123, DOI: 10.11646/phytotaxa.543.2.2, http://zenodo.org/record/645074

The Genus <i>Xanthagaricus</i>: An Updated Global Species Distribution and Phylogeny with the Description of Two New Species from Oman

Xanthagaricus is a saprotrophic mushroom genus with small-sized basidiomata in the family Agaricaceae (Agaricales). Prior to this study, 26 species belonging to this genus have been described and published. In this study, we reported Xanthagaricus for the first time from Oman with the description of two new species. Basidiomata of the new species Xanthagaricus appendiculatus and X. omanicus were collected during the monsoon rains of summer in 2018 in the southern coastal region of Oman. Species descriptions are based on morphological and molecular characterization. Phylogenetic analyses based on internal transcribed spacer region (ITS1-5.8S-ITS2 = ITS) of the nuclear ribosomal DNA clustered the new species in the Xanthagaricus clade with strong statistical support. The new species Xanthagaricusappendiculatus can be distinguished from other species by its purplish pileus with umbonate disc and X. omanicus with the largest pileus (70–90 mm diameter) among the known species of the genus. A detailed description, photographs, line drawings, and a phylogenetic tree showing the position of both new species are provided. A dichotomous key to the known taxa of Xanthagaricus is proposed. Morphological comparisons of new species with known Xanthagaricus taxa are provided. Our observations highlight the diversity of Xanthagaricus and other lepiotaceous mushrooms in southern Oman and further document the need for additional systematic focus on the region’s fungi