Pseudohumicola debertoldii 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 : 107-108

Pseudohumicola debertoldii Sastoque, Cano & Stchigel , nom. nov. MycoBank MB 853457. Fig. 8 .

Replaced synonym: Humicola lutea De Bert., Canad. J. Bot. 54: 2759. 1976, non Pseudohumicola lutea T.O. Condé et al. 2023

Etymology: In honour of Marco de Bertoldi, an Italian mycologist who also isolated this fungus.

Typus: Italy, Sardinia, Sassari, soil from Quercus sp. forest, 1969, coll. and isol. M . de Bertoldi (lectotype designated here CBS H-25748, MBT 10026333, culture ex-type CBS 460.76 = FMR 20616 ) .

On potato carrot agar after 2 wk at 25 °C: Mycelium abundant, composed of hyaline, septate, branched, smooth- and thin-walled, 1–3 μm wide hyphae. Conidiophores absent. Conidiogenous cells integrated to the hyphae. Conidia mostly holoblastic, mostly unicellular, rarely 1-septate, solitary or in clusters, sessile or on short conical denticles or on short side branches, smooth- and thin-walled at first, becoming verruculose and thick-wall with the age, occasionally intercalary (holothallic) ( Fig. 8E ), sub-hyaline to brown, globose, subglobose, oblate, ellipsoid, obovoid, piriform, ovoid, fusiform or cylindric, (4–)7–11(–13) × (4–)7–12(–13) µm, mostly truncated at one end, or at both ends (if intercalary), secession rhexolytic ( Fig. 8E ). Acremonium-like synasexual morph present; conidiophores reduced to a conidiogenous cell; conidiogenous cell phialidic, arising on (discrete) or integrated to (adelophialides) the hyphae, hyaline, simple or 1-branched, flask-shaped (monophialides) or v-shaped (polyphialides) ( Fig. 8F ), 3–12 × 1–3 µm, mostly ventricose at the base and with a long neck that tapers progressively towards the apex; conidia enteroblastic, hyaline, formed basipetally in chains, unicellular, obovoid, 2–4 × 1–2 µm, truncated at the base and rounded at the apex ( Fig. 8F ).

Culture characteristics (after 7 d at 25 ° C): Colonies on PCA 28–30 mm diam., flat and circular; margins entire and regular, brown (5F3) at the centre with radiated stripes showing sparse white (5A1) aerial mycelium at the centre; soluble pigment absent; reverse greyish brown (5E3) at the centre, with radiated dark brown (5F3) stripes and margins uncoloured. Colonies on OA 32–33 mm diam., flat, circular, and expansive; margins filamentous and regular; surface uncoloured, with a floccose white (4A1) aerial mycelium at the centre; soluble pigment absent; reverse uncoloured, cream (4B3) at the centre. Colonies on CMA 25–27 mm diam., flat, circular, and expansive; margins entire and regular; surface sepia (4F4), with a scarce white (5A1) floccose mycelium at the centre, and greyish green (30E5) superficial spots, margins uncoloured; soluble pigment absent; reverse dark green (30F5) at the centre. Colonies on MEA 27–28 mm diam., flat and circular; margins entire and regular; surface dark brown (5E4) with a white (5A1) floccose mycelium at the centre, and margins cream (4B3); soluble pigment absent; reverse similar than the surface. Culture iconography after 2 wk of incubation on PCA, OA, CMA and MEA ( Fig. 8A–D , respectively). Minimum, optimum and maximum temperature of growth on PDA after 7 d: 5 °C, 30 °C and 40 °C, respectively.

Notes: Humicola lutea CBS 460.76 was placed in the same fully supported clade as P. lutea COAD 3127, being consequently transferred to the genus Pseudohumicola as P. debertoldii ( Fig. 1 ). Pseudohumicola debertoldii differs from P. lutea by the production of unicellular, rarely 1-septate conidia, smooth- and thin-walled at first, becoming verruculose and thick-wall with the age, with intercalary (holothallic) conidia, (4–)7–11(–13) × (4–)7–12(–13) µm and the production of an acremonium-like synasexual morph, in contrast to P. lutea , which produces lateral and terminal, single-cell, thick- but smooth-walled conidia, (7.5–)10.8–11.8(–14.5) × (7.2–)10.4– 11.2(–12) μm and lacking an acremonium-like synasexual morph ( Oliveira et al. 2023).

Figures

Fig. 8. Pseudohumicola debertoldii CBS 460.76. A–D. Colony on PCA, OA, CMA, MEA (2-wk-old; 25 °C; surface, left; reverse, right). E. Brown, holoblastic, sessile or on short denticles (DIC). F. Mono- and poly-phialides (black arrow) and conidia in chains (PC). Scale bars = 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.