Botryotrichum pseudomurorum Sastoque, Cano & Stchigel, 2025

Sastoque, A. P., Cano-Lira, J. F. & Stchigel, A. M., 2025, Soil ascomycetes from Spain. XIV. The Chaetomiaceae of La Palma (Canary Islands), Persoonia 54 (1), pp. 93-117 : 97-98

Botryotrichum pseudomurorum Sastoque, Cano & Stchigel , sp. nov. MycoBank MB 847932. Fig. 2 .

Etymology: From Greek ψεῦΔΟ- (pseudo -), false, because the morphological resemblance to Botryotrichum murorum .

Typus: Spain, Canary Islands, La Palma, Fuencaliente (Los Canarios), from soil near the lighthouse, 15 Jul. 2008, coll. M. Calduch & A.M. Stchigel, isol. A.P. Sastoque (holotype CBS H-25345, culture ex-type FMR 19917 = CBS 149965 ) .

On oatmeal agar after 4 wk at 25 °C: Mycelium scarce, mostly aerial, composed of septate, branching, smooth- and thin-walled, subhyaline to brown, 0.5–3 μm wide hyphae. Ascomata superficial, solitary to aggregate, smoke grey to olivaceous grey under reflected light, with greenish setae, ostiolate, neck absent, globose, subglobose, ovoid, or barrel-shaped, 30–105 × 20–100 μm ( Fig. 2E ). Peridial wall translucent, greenish-brown to olivaceous brown, but opaque and nearly black around the ostiole (of up to 30 μm diam.) and medium brown at the base, 3–4-layered, 7–12 μm thick, outer layer of textura intricata, inner layers composed of flattened, translucent polygonal cells of 5–15 μm diam. ( Figs. 2F,G ); terminal hairs abundant around the ostiole, septate, straight, undulate and verrucose at the upper part ( Fig. 2H ), pointed or circinate at the apex, greenish-brown to olivaceous grey, mostly up to three times longer than the ascomata diameter, 5–7.5 μm wide at the base, branching; lateral hairs straight, septate, greenish brown to olivaceous grey, up to 150 μm long, covered with cup-shaped ornamentations specially at the base, pointed or rounded at the tip ( Fig. 2E ). Asci unitunicate, fasciculate, clavate to fusiform, spore-bearing part 36–51 × 13–20 μm, stalks 16–25 μm long, with 8 irregularly-arranged or biseriate ascospores, evanescent before ascospores become mature ( Fig. 2I ). Ascospores unicellular, pale pinkish brown when young, brown but irregularly coloured (varying the intensity of colour) when mature, smooth-walled, but with slight irregularity in wall thickness, broadly fusiform, (12–)13–14(–15) × (7–)7.5–8(–8.5) × 7–8 μm, attenuated at both ends, with a germ pore at one end ( Fig. 2J ). Asexual morph not seen.

Culture characteristics (after 7 d at 25 ° C): Colonies on PCA 8–9 mm diam., flat, circular, and expansive; margin filamentous, slightly- and irregularly undulate; surface yellowish grey (4B2) with black (6F3) ascomatal covered by almond green (28E3) terminal hairs and scarce white (4A1) aerial mycelium in the central area; soluble pigment absent; reverse nougat (5D3) and marble white (5B2) margins. Colonies on OA 30–31 mm diam., flat, circular, and expansive; margin entire and regular; surface golden blonde (4C4) with scarce white (3A1) erect aerial mycelium; soluble pigment absent; reverse greyish yellow (4C5). Colonies on CMA 18–19 mm diam., flat, circular, and expansive; margin filamentous and lobulated to irregular; surface without aerial mycelium camel (6D4) and yellowish white (3A2) margins; soluble pigment absent; reverse light brown (6D5). Colonies on MEA 14–15 mm diam., flat to slightly convex; margin entire and irregularly-lobulated; surface golden blonde (5C4) with floccose white (5A1) aerial mycelium and pale yellow (3A3) margins without aerial hyphae; yellow soluble pigment; reverse butter yellow (4A5) and yellowish white (3A2) margins. Culture iconography after 4 wk of incubation on PCA, OA, CMA and MEA ( Fig. 2A–D , respectively). Minimum, optimum and maximum temperature of growth on PDA after 7 d: 5 °C, 20 °C and 35 ºC, respectively.

Notes: Botryotrichum pseudomurorum was placed in the fully-supported clade corresponding to the species of the genus Botryotrichum (B.), but in a separate branch flanked by Botryotrichum murorum CBS 163.52 and Botryotrichum spirotrichum CBS 211.55 ( Fig. 1 ). Botryotrichum pseudomurorum differs from Botryotrichum murorum by the larger ascomata (160–320 × 150–270 μm in B. murorum ), and the verrucose and longer terminal hairs (usually over four times longer than ascomata (up to 3 mm long). Additionally, B. pseudomurorum is distinguished by the production of a yellow soluble pigment on MEA, a characteristic not described for B. murorum ( Corda 1837, Wang et al. 2016a). While most Botryotrichum spp. have been reported from dung, air, wood or soil, they have not been specifically isolated from volcanic soils as the case of B. pseudomurorum ( Wang et al. 2016a, https://wi.knaw.nl/fungal_table, accessed on 21 February 2024). Like B. murorum , B. piluliferum , B. spirotrichum and B. verrucosum , which are mesophiles and have an optimal growing temperature of 20−30 °C ( Corda 1837, Pugh et al. 1964, Domsch et al. 1980, von Arx 1985, Asgari & Zare 2011), B. pseudomurorum exhibit a rapid growth between 5 and 35 °C. However, B. verrucosum shows slow growing at 37 °C, indicating a less thermotolerance than the former species ( Pugh et al. 1964). Since B. pseudomurorum was isolated using the ToKaVa technique, suggesting the ability to use the keratin as source of nutrients by enzymatic digestion, further tests are required to confirm this assumption.

Figures

Fig. 2. Botryotrichum pseudomurorum CBS 149965. A–D. Colonies on PCA, OA, CMA, MEA (4-wk-old; 25 °C; surface, left; reverse, right). E. Mature ascomata. F. Detail of the peridium. G. Detail of the ascomata wall, indicating the peridial layers (black line). H. Verrucose upper part of the terminal hairs. I. Asci and ascospores. J. Ascospores showing the variation of the cell wall thickness (as longitudinal striations) and the apical germ pore. Scale bars: E = 50 μm; F–I = 10 μm.

Fig. 1. Maximum likelihood of the tree obtained from the concatenated ITS-LSU-rpb2-tub2 (3215 bp) alignment of the nucleotide sequences from our strains and those retrieved from the GenBank. Bayesian posterior probabilities (PP) ≥ 0.95 and the RAxML bootstrap support values (BS) ≥ 70 % are presented at the nodes (PP/BS). Thickened branches indicate full support (PP = 1 and BS = 100 %). The new species and combinations are indicated in bold. T represents the ex-type strain of the species. NT represents the ex-neotype strain of the species.