Leucoagaricus margallensis Ashraf, S., Naseer, A. & Khalid, A.N., 2023

Ashraf, Shazia, Naseer, Arooj, Usman, Muhammad & Khalid, Abdul Nasir, 2023, Two new species of genus Leucoagaricus (Agaricaceae, Agaricales) from Pakistan, MycoKeys 96, pp. 159-171 : 159

Leucoagaricus margallensis Ashraf, S., Naseer, A. & Khalid, A.N. sp. nov.

Figs 3 , 4

Etymology.

The specific epithet margallensis (Latin) refers to type locality Margalla.

Diagnosis.

Leucoagaricus margallensis can be distinguished by small, umbonate pileus with minute, fragile annulus, bulbous stipe, smaller basidiospores (6.27 × 4.67 µm) and cheilocystidia without crystals on its apex.

Holotype.

Pakistan, Islamabad, Margalla Hills National park, trail 5, 33°45'01.1"N, 73°05'14.5"E, 1303 m.a.s.l., July 27, 2018, Shazia Ashraf & Arooj Naseer, MH-63, Holotype (LAH 37543), GenBank: OP605606 (ITS), OP782026 (LSU).

Description.

Basidiomata medium-sized, shiny, smooth, moderately fleshy, solitary. Pileus 1.5-2.5 cm in diameter, hemispherical to parabolic when young, expanding convex to plano convex, plane at maturity, umbonate, radially fibrillose to rugulose, whole pileus orange (0.5YR 3.2/8.7) when immature, then yellowish orange (9.4YR 6.1/7.2) on maturity, margin incurved in mature and striated, context white, smooth, thick at center. Lamellae free to thin, milky white (2.2GY 6.8/0.9), spacing fine and close, 1-1.5 mm wide, edges entire, lamellae regular, 3-4 tiers. Lamellulae irregular, alternating with lamella, in 2-3 tiers. Stipe 4.5-7 × 0.5-1 cm, cylindrical, central, thin, white (2.2GY 6.8/0.9), smooth, shiny, even, clavate. Annulus simple, white, located in upper half of stipe, membranous upturned. Flavor and odor not distinctive.

Basidiospores [90/5/3] (6-) 6.2 - 8.0 (-8.2) × (3.43-) 4.11 - 4.7(-4.9) µm, 6.1-8.1 × 3.7-4.8 µm, av. Q = 1.58-1.42, Qav = 1.49, hyaline to light yellowish in 5% KOH, oval to ellipsoid at face view, lacrymoid to amygdaliform in side-view, guttulate, smooth, dextrinoid, thin-walled and apiculate. Basidia (12.06-) 13.08 - 23.5 (-24.03) × (6.86-) 7.7 - 8.72 (-9.72) µm, 12.9-18.5 × 5.8-7.7 µm, av. L =19.29 µm, av. W = 7.54 µm, narrowly clavate, hyaline in 5% KOH, smooth, with 2-4 prominent sterigmata, oil droplets present,no clamp at base. Cheilocystidia (15.12-) 16.12 - 24.9 (-25.98) × (6.88-) 7.8 - 8.4 (-9.43) µm, 15-26 × 6.8-9.4 µm, hyaline in 5% KOH, thick-walled, broadly clavate and smooth, without internal content and clamp. Pleurocystidia absent. Pileipellis an intricate trichoderm, made up of 5.6-7.7 µm, av w=5.99 µm, wide, septate, interwoven, thin-walled hyphae, hyaline in 5% KOH, clamp connections absent.

Stipitipellis as compactly arranged cutis, made up of septate, cylindrical hyphae, 3.4-4.9 µm in diam., thin-walled, light yellowish in 2% KOH, clamp connections absent.

Additional specimen.

Pakistan, Islamabad, Margalla Hills National park, trail 5, 33°45'01.1"N, 73°05'14.5"E, 1303 m a.s.l., July 22, 2021, Shazia Ashraf, MH-111(LAH 37454), GenBank for ITS (OP605607) LSU (OP782027).

Comments.

Leucoagaricus margallensis has a combination of striking features like small, umbonate pileus with minute, fragile annulus and broader bulbous stipe. Anatomically, it has smaller basidiospores (6.27 × 4.67 µm), smaller cheliocystidia and absence of crystals at apex of cheliocystidia.

Leucoagaricus margallensis resembles La. rubrotinctus including similar pileus size and shape, fibrillose surface, stipe color and shape. But Leucoagaricus margallensis differs from La. rubrotinctus by minute fragile annulus while La. rubrotinctus has prominent white annulus. Anatomically, Leucoagaricus margallensis has ellipsoid, smaller (6.27 × 4.67 µm) basidispores as compared to La. rubrotinctus larger and amygdaliform basidiospores. Furthermore, Leucoagaricus margallensis has smaller cheliocystidia (15-26 × 6.8-9.4 µm) as compared to La. rubrotinctus (30-50 × 5-10 µm), narrow pilleipellis hyphae (5-10 µm) in La. rubrotinctus . The other closely related taxa in phylogenetic tree is L. rubroconfusus Migl. & Coccia, characterized by centrally depressed, larger (up to 7.5 cm) pileus with orange fibrillose squamules as compared to umbonate, smaller (2.5 cm) yellowish orange fibrils on white pileus of Pakistani taxon. Anatomically, both taxa lack crystals at apex of cheilocystidia. Our taxon Leucoagaricus margallensis is differentiated from L. rubroconfusus due to smaller (6.27 × 4.67 µm) basidiospores as compared to basidiospores of L. rubroconfusus (5.5-8(9.5)) µm.

Leucoagaricus subpurpureolilacinus Z.W. Ge & Zhu L. Yang, from southwestern China differs in its broad, brown to dark ruby umbo, larger basidiospores and clavate cheilocystidia with gelatinized covering intermixed with crystals ( Ge et al. 2015). Our taxon can also be differentiated from La. purpureolilacinus . Leucoagaricus purpureolilacinus has a pinkish brown pileus with a dark purple brown disk, a stipe attenuating toward the base, amygdaliform spores and clavate cheilocystidia often with constrictions in the middle ( Vellinga 2001).

Figures

Figure 3. Morphological description of Leucoagaricus spp. from Pakistan A, C Leucoagaricus margallensis B, D Leucoagaricus glareicolor.

Figure 4. Anatomical features of Leucoagaricus margallensis A basidia B basidiospores C cheilocystidia D pileipellis E stipitipellis. Scale bars: 10 µm (A); 5 µm (B-E).