Laxitextum subrubrum R. Saha, A.K. Dutta & K. Acharya, sp. nov.
Index Fungorum number: IF 559644; Mycobank number: MB 59644; Facesoffungi Number: FoF 11347; Figs. 1, 2
Etymology – Named after sub- (Latin)=under, almost, and rubrum (Latin)=red, referring to the reddish or dull red colouration of the pileus.
Holotype – CUH AM774.
Basidiomes pileate, sessile, soft-spongy when fresh and brittle on drying, 10–30 mm long, 5–20 mm wide and up to 1–2 mm thick. Pileus upper surface uneven, slightly zonate, velutinous, dull red (9C4). Margin thin, wavy, brownish orange (7C3). Hymenophore smooth, white (1A1), cracked on drying. Context soft, thin, dull red (9C3).
Hyphal system monomitic, generative hyphae 2.9–5.9 µm wide, hyaline, thin- to thick-walled, clamped. Oleiferous hyphae 3.5–6.5 µm wide. Gloeocystidia 102–156×8.5–15 µm, lanceolate, sometimes apex moniliform, pale orange (5A3), filled with oily substance. Basidia 23.5–38×5.5–9 µm, narrowly clavate, hyaline, thin-walled, 4-sterigmate, with basal clamp. Basidiospores (3.5–)4.74–5.9×(2.9–)3.06–3.5 µm, Q=1.2–2, Qm =1.54, thin-walled, hyaline, ellipsoid, apiculate, finely echinulate, strongly amyloid in Melzer’s reagent.
Habitat and distribution – The new species grows on dead wood of unknown angiosperm, and is currently only found in India.
Material examined – India, West Bengal, Jalpaiguri District, Moraghat range, Khuttimari, 26.4728°N, 88.5957°E, elevation 144 m alt., on dead wooden logs of unknown angiosperm, 7 October 2018, R. Saha & K. Acharya, CUH AM774 (holotype), 8 October 2018, R. Saha, K. Acharya, CUH AM775.
GenBank numbers – CUH AM774: ITS = ON227060, LSU = ON226874; CUH AM775: ITS = ON227061, LSU=ON227065.
Notes – Characteristic features of the present specimens include pileate, sessile basidiomes with slightly zonate, velutinous, dull red upper surface; brownish orange margin, smooth, white hymenophore; dull red context; presence of a monomitic hyphal system with clamped generative hyphae; lanceolate, pale orange gloeocystidia, apex sometimes moniliform; narrowly clavate, hyaline, thin-walled, 4-sterigmate basidia; and thin-walled, hyaline, ellipsoid, apiculate, finely echinulate, strongly amyloid in Melzer’s reagen basidiospores measuring 3.5–5.9×2.9–3.5 µm.
Among similar taxa, Laxitextum bicolor differs by having resupinate to effused-reflexed basidiomes; brown coloured and finely tomentose pileus upper surface with appressed hyphal hairs (Lentz 1955). Laxitextum incrustatum differs by the presence of resupinate and widely effused basidiomes; white to pallid, cottony to matted tomentose margin; tubular gloeocystidia, sometimes with a bulbous swelling near base and hyphidia (Hjortstam and Ryvarden 1981). Laxitextum lutescens differs by having resupinate to distinctly reflexed basidiomes; deep yellow to pale brown velutinous, azonate pileus upper surface; cream-yellowish to straw coloured hymenium with a light purple-brown tint (Hjortstam and Ryvarden 1981).
In the phylogenetic tree, Laxitextum subrubrum appears to be close to Laxitextum cf. bicolor (83% MLBS, 0.65 BYPP; Figs. 3 and 4). However, details of Laxitextum cf. bicolor cannot be verified because of lacking any morphological details in the form of published literature.
Figure 1 – Laxitextum subrubrum (CUH AM774, holotype). a, b Field pictures of the basidiomes. c SEM image of basidiospore. Scale bars: a–d=5 mm, c=1 µm
Figure 2 – Laxitextum subrubrum (CUH AM774, holotype). a Basidia. b gloeocystidia. c Oleiferous hyphae. d generative hyphae. e basidiospores. Scale bars: a–e=5 μm
Figure 3 – Phylogenetic analyses were based on data set of nrDNA ITS sequences. Reference sequences were selected from relevant literature (He and Zhao 2022; Hofstetter et al. 2019), BLAST searches (Altschul et al. 1997) and data retrieved from GenBank (Clark et al. 2016). Two sequences of the genus Gloeophyllum, was chosen as the outgroup for rooting purpose (He and Zhao 2022). ClustalX2 (Thompson et al. 1997) with the use of default settings, and finally the alignment was upgraded wherever needed using MEGA v. 7.0 (Kumar et al. 2016) for manual adjustments. For maximum likelihood (ML) analyses, the statistically best fit models of nucleotide substitution using Cyber Infrastructure for Phylogenetic Research (CIPRES) web portal (https://www.phylo.org/portal2/) were determined by jModeltest 2.1.6 (Darriba et al. 2012) on XSEDE (Miller et al. 2010). Based on the Bayesian information criterion (BIC), the GTR+I+G (10,768.817815) model chosen as the most suitable model for the alignment. Maximum Likelihood analysis was performed using RAxML-HPC2 ver. 8.2.12 (Stamatakis 2006) with bootstrap statistics worked out from 1000 rapid bootstrap replicates on the CIPRES NSF XSEDE resource. Bayesian inference (BI) of the phylogeny was worked out with the application of MrBayes v.3.2.2 (Ronquist et al. 2012) using the selected model operating Markov chain Monte Carlo (MCMC) analyses (Geyer 1991). Bayesian analyses extended to a standard deviation of split frequencies of 0.002 after 106 generations. After 25% preliminary burn in (Hall 2004), MrBayes was used to figure out the remaining trees’ 50% majority rule consensus phylogram to enumerate the PPs (posterior probabilities) of the groups. MLBS and PP values over 50% and 0.50 are displayed in the resulting phylogenetic tree. The newly described species are exhibited in black bold font to highlight its position in the phylogenetic tree
Figure 4 – Phylogenetic analyses were based on data set of nrDNA LSU sequences. Reference sequences were selected from relevant literature (He and Zhao 2022; Hofstetter et al. 2019), BLAST searches (Altschul et al. 1997) and data retrieved from GenBank (Clark et al. 2016). Two sequences of the genus Gloeophyllum, was chosen as the outgroup for rooting purpose (He and Zhao 2022). ClustalX2 (Thompson et al. 1997) with the use of default settings, and finally the alignment was upgraded wherever needed using MEGA v. 7.0 (Kumar et al. 2016) for manual adjustments. For maximum likelihood (ML) analyses, the statistically best fit models of nucleotide substitution using Cyber Infrastructure for Phylogenetic Research (CIPRES) web portal (https://www.phylo.org/portal2/) were determined by jModeltest 2.1.6 (Darriba et al. 2012) on XSEDE (Miller et al. 2010). Based on the Bayesian information criterion (BIC), the GTR+I+G (5221.325866) model chosen as the most suitable model for the alignment. Maximum Likelihood analysis was performed using RAxMLHPC2 ver. 8.2.12 (Stamatakis 2006) with bootstrap statistics worked out from 1000 rapid bootstrap replicates on the CIPRES NSF XSEDE resource. Bayesian inference (BI) of the phylogeny was worked out with the application of MrBayes v.3.2.2 (Ronquist et al. 2012) using the selected model operating Markov chain Monte Carlo (MCMC) analyses (Geyer 1991). Bayesian analyses extended to a standard deviation of split frequencies of 0.002 after 106 generations. After 25% preliminary burn in (Hall 2004), MrBayes was used to figure out the remaining trees’ 50% majority rule consensus phylogram to enumerate the PPs (posterior probabilities) of the groups. MLBS and PP values over 50% and 0.50 are displayed in the resulting phylogenetic tree. The newly described species are exhibited in black bold font to highlight its position in the phylogenetic tree