Figures 2, 3

MycoBank No.: MB842566

Etymology:—‘ radiatosquamulosus refers in Latin refers to the radial arrangement of squamules on pileus surface.

Species-specific ITS markers:—tgttact[T]ttttgta

Main Characteristics:—This species is distinguished by having irregular and lumpy surface, brown roughly triangular squamules on pileus covering radiating towards margin, light pinkish brown discoloration at stipe base when cut, thick rhizomorph observed at pointed base of stipe, basidia monosporic (in N-224), frequently bisporic, tetrasporic also observed, cheilocystidia clavate to broadly clavate, Schäffer’s reaction positive but weak with faint orange color with reddish tint at stipe base of dry material.

Type:— PAKISTAN. Punjab, University of the Punjab, Lahore, at 217 m a.s.l., solitary on rich loamy soil on the grassy grounds in Botanical Garden, 7 November 2017, Aiman Izhar, BG01 (holotype: LAH35769 ), GenBank ITS # ON490922.

Description:— Pileus 3–5 cm in diam., convex to applanate, irregular, uneven or lumpy, covered by brown (4.8YR 5.3/2), roughly triangular, adpressed squamules, dense at disc then sparse towards margin, disc adpressed and rounded in BG01 and depressed in N-224, white to creamy (7.2PB 8.3/0.6) background, triangular shaped, no significant effect when rubbed, margins slightly appendiculate, entire, wavy, irregular, slightly exceeding lamellae. Surface dry and dull, irregular having small depressions and slightly uplifted spots throughout the surface (Figures 2A–C). Lamellae pink to dark brown, free and approximate, regular, edges entire, crowded, intercalated with lamellulae (Figure 2D). Stipe 4–5.5 × 0.5–1 cm, centrally attached, creamy white (3.8PB 7.7/1.3) with concolorous squamules, light pink below annulus, cylindrical, stuffed having annulus on its upper third part, color changed to light pinkish brown on rubbing or bruising, solid, provided with thick rhizomorph at the base (more evident in N-224) (Figure 2E, F). Annulus superous, membranous, double edged, striated on upper side, slightly fibrillose on under side, initially white then margin turning dark brown, ring zone observed in BG01 and pendent in N-224 at maturity, labile (Figure 2E, F). Context up to 5 mm thick in pileus, fleshy, white, solid, light pinkish brown discoloration at stipe base when cut. Odor mild, aniseed like.

KOH reaction positive, light yellow; Schäffer’s reaction positive but weak on stipe base in dried specimens, faint orange with reddish tint.

Basidiospores (5.5–) 6–6.5 (–6.9) × (3.8–) 4.1–4.5 (–5) µm, [avX = 6.5 ± 0.59 × 4.01 ± 0.42, Q m = 1.76, n = 2 × 50], brown in KOH with dark brown walls, broadly ellipsoid, rarely guttulate, smooth with a prominent apiculus (Figure 3A). Basidia (21.7–) 22–24.3 (–27.7) × (5.1–) 6.4–7.6 (–8.9) µm, [avX = 24.7 ± 2.96 × 7 ± 1.93 µm], thin walled, hyaline in KOH, broadly clavate, bisporic but mainly tetrasporic observed in BG01 specimen, frequently monosporic to bisporic observed in N-224, olivaceous granular contents abundant (Figure 3B). Cheilocystidia (14.3–) 15–16.9 (–18.6) × (5.8–) 6.1–7 (–7.7) µm, [avX = 16.9 ± 2.14 × 6.8 ± 0.92 µm], thin walled, hyaline in KOH, clavate to broadly clavate, olivaceous granular contents present (Figure 3C). Lower surface of annulus composed of two types of hyaline hyphae, cylindrical, frequently septate, vaguely constricted at septa with blunt ends, 2.5–12 µm in diam., others short, inflated elements with rounded ends, distinctly constricted at septa, 20–32 µm in diam. (Figure 3D). Pileipellis hyphae 4.3–11 µm in diam., [av = 7.9 µm], hyaline in KOH, septate, irregular in arrangement, branched, pileipellis trichoderm (Figure 3E). Stipitipellis hyphae 3.25–16.01 µm in diam., [av = 8.9 µm], hyaline in KOH, irregular in arrangement, branched, broad, septate (Figure 3F).

Habit, habitat, and distribution:—Solitary on loamy soil under Dalbergia sissoo or in groups on grassy grounds of the Botanical Garden of the University of Punjab.

Additional materials examined:— PAKISTAN. Punjab, Chichawatni, on soil in the grounds of Chichawatni Forest, at 164 m a.s.l. under Dalbergia sissoo, 9 August 2019, Nadia Fatima, N-224, (LAH36965), GenBank ITS # ON490923.

Taxonomic comments:—Within A. sect. Fulventes, Agaricus sp. (ADK2171) is the closest related species to A. radiatosquamulosus and is briefly described in Ortiz-Santana et al., (2021). It could be necessary to compare the ITS sequences, which differ at four positions, to reliably distinguish these two species from each other. In the genus Agaricus, molecular data are often required for a 100% reliable identification. Spore size comparison in Table 2 shows that this trait is not very efficient to distinguish the species of A. sect. Fulventes from each other. In addition, cap diameter can be used only to distinguish Agaricus nanofulvens, which has a much smaller cap diameter (reaching up to 2.2 cm) than the other species. In addition, it differs from A. radiatosquamulosus, by the annulus with a smooth upper surface observed in the former while striated in the later species. In addition, cheilocystidia are absent in A. nanofulvens but clavate to broadly clavate in A. radiatosquamulosus.

Agaricus radiatosquamulosus is known from Punjab Province of Pakistan and likely from India according to our phylogenetic analyses. Indeed, the clade corresponding to this taxon includes five sequences of specimens from India. Unfortunately, none of these sequences retrieved from the GenBank are taxonomically documented even the only one (CBS638.89) associated with a publication (Vu et al. 2019).

Several characteristics agree well with the description of A. sect. Fulventes. such as brown pileus covering, presence of annulus on upper third, annulus superous, distinct rhizomorphs at the base of stipe, Schäffer’s reaction positive but weak on stipe base in dried specimens, annulus with few inflated cells. This species is known from the Punjab Province of Pakistan and likely from India according to unpublished information found in sequence or strain repositories until now.