Chlorophyllum squamulosum A.K. Dutta, Soumili Bera & K. Acharya, Phytotaxa 451: 121 (2020).
Index Fungorum number: IF 835117; MycoBank number: MB 835117; Facesoffungi number: FoF 10684. Fig. 1
Basidiomata agaricoid, medium to large. Pileus 50–75 mm in diam., convex to broadly convex, often with a shallow central depression, sometimes with an upturned margin with age; surface white to cream, covered with squamules, entire at the disc, elsewhere disrupting in some specimens, mostly small plate-like, arranged in a concentric manner from center towards the margin, flat or curved upwards, greyish brown (8E3) to reddish-brown (8E4) or dark brown (8F5) at the center, elsewhere greyish brown (8D3) to brownish grey (7C2) or dull red (9C3). Lamellae 4–6 mm broad, adnexed, crowded with two series of lamellulae, white to cream, concolorous; edge even to slightly wavy, yellowish with KOH. Stipe 60–90×9–12 mm, central, cylindrical, gradually broader towards the base, at base 15–27 mm wide and bulbous to subbulbous, hollow, white (6A1), turning brown (6D6–6E7) on bruising or with KOH. Annulus double; upper portion concolorous with the stipe surface; lower portion white to cream, sometimes with greyish brown (8D3) to reddish-brown (8E4) at the margin, rarely with a brownish border; edge sometimes floccose.
Basidiospores 7.5–12×5–7.5 μm (n=50), Q=1.25–1.85, Qm = 1.5 ± 0.13, ellipsoid, smooth, hyaline, dextrinoid, with a prominent wide germ-pore, truncated, thick-walled; apiculus short, 0.5–1 μm long. Basidia 25–50×8–10 μm, cylindrical to clavate or subclavate, thin-walled, 4-spored, sterigmata upto 10 μm long, cylindrical. Pleurocystidia absent. Cheilocystidia 17–25 × 7.5–12 μm, clavate or spheropedunculate, hyaline, thin-walled. Annulus hyphae 3–7 μm broad, tightly arranged, hyaline, often branched, hyphal end obtuse to clavate, thin-walled. Pileipellis (pileal squamules) a tightly packed hymeniderm, with cylindrical and flexuous, or narrowly clavate terminal elements, measuring 5–12.5 μm broad, with pale brown intracellular pigments, often incrusted, sometimes branched, thin-walled. Pileus trama hyphae 7–14 μm broad, incrusted, thin-walled. Stipitipellis hyphae 5–10 μm broad, parallel to subparallel, light yellowish with KOH, sometimes branched, nonincrusted, thin-walled. Stipe trama hyphae 5–12 μm broad, incrustations present, parallel to subparallel, thin-walled. Caulocystidia absent. Clamp connections absent in all the tissues.
Material examined – Thailand, Chiang Mai Province, Muang District, Chiang Mai University, 18°48′2″N 98°57′18″E, elevation 335 m, solitary on soil in grassland, 3 August 2019, J. Kumla, SDBR-CMUNK0585, 18°48′14″N 98°57′15″E, elevation 333 m, solitary on sandy humus mixed soil, 26 July 2020, J. Kumla, SDBR-CMUNK0731.
Habitat – Solitary, on sandy humus mixed soil in the dry deciduous forests and grassland.
Distribution – Known from India and Thailand (Dutta et al. 2020; this study).
GenBank numbers – SDBR-CMUNK0585- MZ452085 (ITS), MZ452086 (LSU) SDBR-CMUNK0731- MZ452084 (ITS), MZ452070 (LSU)
Notes – Chlorophyllum squamulosum belongs to the Chlorophyllum section Rhacodium based on a combination of morphological and molecular data (Fig. 2). Morphologically, C. squamulosum is similar to C. nothorhacodes, C. rhacodes, C. olivieri and C. brunneum by its brownish to reddish colouration of the stipe upon bruising, truncated basidiospores and clavate cheilocystidia. The phylogenetic tree indicated that C. squamulosum formed a sister taxon to C. nothorhacodes. However, C. nothorhacodes differs from C. squamulosum by its much larger basidiocarp (pileus of up to 280 mm in diam. and stipe up to 250 mm × 25–60 mm) (Vellinga 2003a). Furthermore, C. rhacodes differs from C. squamulosum by its broader basidiospores (9.8–11.1 × 6.3–7.7 μm), comparatively larger cheilocystidia (16–43 × 8.5–25 μm) and the presence of clamp connections in the basidia, cystidia and tramal hyphae (Vellinga 2001, 2003b). Chlorophyllum olivieri has clamped basidia and broader cheilocystidia (35–45 μm) when compared with C. squamulosum (Vellinga 2001). Chlorophyllum brunneum differs from C. squamulosum by the presence of clamp connections at the base of the basidia and cystidia (Bougher and Syme 1998; Vellinga 2002, 2003a).
Figure 1 – Chlorophyllum squamulosum (SDBR-CMUNK0585, new record). a. Basidiomata. b. Basidiospores. c. Basidia. d. Cheilocystidia. Scale bars: a=50 mm; b=5 μm; c, d=10 μm
Figure 2 – Phylogenetic tree derived from maximum likelihood analysis of a combined ITS and LSU genes of 38 sequences and the aligned dataset was comprised of 1613 characters including gap. The average standard deviation of the split frequencies of the BI analysis was 0.00481. Agaricus megacystidiatus (MFLU 12–0137) and Xanthagaricus flavosquamosus (GDGM50918) were used as outgroup taxa. The numbers above branches are the bootstrap statistics percentages (left) and Bayesian posterior probabilities (right). Branches with bootstrap values≥70% are shown at each branch and the bar represents 0.1 substitutions per nucleotide position. Hyphen (-) represents support values≤70%/0.90. Ex-type strains are in black bold. The newly generated sequences are indicated in blue