Hygrocybe boertmannii U. Singh & R.P. Bhatt, sp. nov.
Index Fungorum number: IF 557840; MycoBank number: MB 557840; Facesoffungi number: FoF 07737; Fig. 1
Etymology – In recognition to David Boertmann for his contribution to the wild mushrooms.
Holotype – CAL 1802
Pileus 12–52 mm in diam., convex when young, becoming planoconvex to applanate or slightly depressed with age, non-striated, non-perforate, dry, non-viscid, orange to deep orange (5A7-5A8), with maize yellow to sunflower yellow (4A6-4A7) fibrillose-squamules on the surface; margin decurved to plane, crenate; context up to 2 mm wide, fragile, concolorous towards cap surface and pastel yellow to light yellow (3A4-3A5) towards lamellae. Lamellae up to 7 mm wide, sub-decurrent to decurrent or sometimes sinuate, distant, white when young, becoming yellowish white (2A2-2A3), edges concolorous but white near the stipe attachment, with about 3 complete lamellae (at margin) per cm, and usually with 3 lamellulae of different lengths between the two complete lamellae, often interveined. Stipe 51−116×6−11 mm, central, tapered towards apex, curved near base in mature specimen, smooth, maize yellow to sunflower yellow (4A6-4A7), yellowish white (2A2) at base, hollow; context thin, concolorous to surface, fragile. Spore deposit white. Taste and odour indistinct. Spore print not obtained. Basidiospores (8–)8.7−9.8−10.9(−11)×(6−)6.8−7.6−8.4(−9) μm (Q=(1.1−)1.2−1.3−1.4 μm, n=30), broadly ellipsoid to ellipsoid, rarely subglobose, smooth, thin-walled, hyaline, inamyloid, single to multi-guttulate, with apicules up to 1 μm long. Basidia 62–78×11–13 μm, clavate to narrowly clavate, thin-walled, turning light yellowish brown with KOH, with a basal clamp connection, 4-spored; sterigmata up to 13×4 μm. Lamellar edge nonfertile. Cystidia-like hyphoid elements 22–38×4–5 μm, emanating from the lamellar context, clavate to cylindro-clavate, fusiform, rarely ventricose; frequently clamped at bases. Hymenophoral trama subregular, composed of hyaline, thin-walled (up to 1 μm), cylindrical elements (26–51×5–7 μm) intermixed with inflated cells (30–75×10–16 μm), rarely with clamp connections. Pileipellis a trichoderm, made up of erect to semi-erect septate, thin-walled, unbranched hyphae; terminal elements 74–118×10–20 μm, with round apex, rarely pointed apex, clamp connections absent; underlying hyphae repent, cylindrical, rarely clamped, devoid of any pigments. Stipitipellis composed of septate, thin-walled, unbranched hyphae, up to 21 μm wide; clamp connection present.
Material examined – INDIA, Uttarakhand, Rudraprayag district, Baniyakund forest, growing scattered on ground under Quercus sp. in mixed temperate forest, 2653 msl, N30°28.998′ E079°10.658′, 08 August 2017, U. Singh, US 1552 (CAL 1802, holotype); 2617 msl, N30°28.926′ E079°10.615′, 25 August 2016, U. Singh, US 1358 (CAL 1803, paratype).
GenBank numbers – ITS=MT127548, MT127549.
Notes – Hygrocybe boertmannii is characterized by orange to deep orange pileus with yellowish fibrillose-squamules all over the pileus, crenate margin, white to yellowish distant lamellae, smooth yellow stipe, broadly ellipsoid to ellipsoid basidiospores, presence of cystidia-like hyphoid elements and a trichoderm nature of pileipellis (Fig. 1). Based on a combination of characters, e.g., dry basidiomata, squamulose pileus, smooth stipe, subregular hymenophoral trama and a trichoderm pattern of the pileipellis, it is referable to H. subsect. Squamulose (Borgen and Arnolds 2004; Boertmann 2010; Lodge et al. 2014). This placement was further confirmed by our ITS-based molecular phylogeny (Fig. 2). Hygrocybe boertmannii shares some similarities with H. cantharellus (originally described from USA) including having orange pileus with crenate margin, the presence of squamulose on pileus, yellow distant lamellae and a smooth stipe surface but the latter can be distinguished by smaller basidiomata (pileus 7–30 mm; stipe 18–67× 1.8–4 mm), weakly to strongly arcuate decurrent lamellae, ellipsoid to ovoid basidiospores, smaller basidia (35–54×7.5–9.5 µm) and absence of cheilocystidia (Arnolds 1995).
Figure 1 – Hygrocybe boertmannii (US 1552, holotype). a Fresh basidiomata in the field. b Pileus surface with fine squamules. c Lamellae with lamellulae d Cystidia-like hyphoid elements. e Transverse section through hymenium showing basidia and basidiospores. f Terminal elements of pileipellis. Scale bars: a=25 mm, d, e=10 µm, f=20 µm
Figure 2 – Phylogenetic analyses were based on data set of nrITS sequences. Reference sequences were selected from relevant literature (Lodge et al 2014; Singh et al. 2017), BLAST searches (Altschul et al. 1997) and data retrieved from GenBank (Clark et al. 2016). Species of Hygroaster are selected as the outgroup taxa (Lodge et al 2014; Singh et al. 2017). Multiple sequence alignment was performed using MAFFT v.7 (Katoh and Standley 2013). Alignments were manually edited in BioEdit v 7.2.5 (Hall 1999). To change the multiple alignment format, Alignment Transformation Environment (ALTER) was used (Glez-Peña et al. 2010). Maximum Likelihood analysis was performed with the programme RAxML GUI 1.5 (Silvestro and Michalak 2012). One thousand bootstrap replicates were analysed to obtain nodal support values. Bayesian inference was computed independently twice in MrBayes v.3.2.2 (Ronquist et al. 2012), under different models. The best-fit substitution model of nucleotide evolution was carried out in MrModeltest 3.7 (Posada and Crandall 1998). Bayesian posterior probabilities (BPP) were calculated in two simultaneous runs with Markov chain Monte Carlo (MCMC) algorithm (Larget and Simon 1999). Markov chains were run for 10 million generations, saving a tree every 100th generation. Default settings in MrBayes were used for the incremental heating scheme for the chains (3 heated and 1 cold chain), unconstrained branch length [unconstrained: exponential (10.0)] and uniformative topology (uniform) priors. The first 25% of trees was discarded as burnin (Hall 2004). Ex-type strains are in black bold and newly generated sequences are indicated in blue