Micropsalliota ventricocystidiata Al-Sadi & S. Hussain, 2022

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, Phytotaxa 543 (2), pp. 113-126 : 119-123

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.

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.

Figures

FIGURE 3. Basidiomata of Micropsalliota ventricocystidiata. A, B, D: Holotype (SQUH-GOB002), C: SQUH-ATR004. Scale bars: 20 mm.

FIGURE 4. Line drawing of anatomical characters of Micropsalliota ventricocystidiata (SQUH-GOB002).A. Basidiospores, B. Basidia, C. Cheilocystidia, D. Pileipellis. Scale Bars:A = 6 µm, B–D = 15 µm.