Pseudobaeospora deceptiva Vizzini, Consiglio, Setti & Adamčík, 2025

Vizzini, Alfredo, Consiglio, Giovanni, Adamčíková, Katarína, Setti, Ledo & Adamčík, Slavomír, 2025, Pseudobaeosporoideae, a new subfamily within the Tricholomataceae for the genus Pseudobaeospora (Agaricales, Tricholomatineae) based on morphological and molecular inference, IMA Fungus 16, pp. e 144994-e 144994 : e144994-

Pseudobaeospora deceptiva Vizzini, Consiglio, Setti & Adamčík sp. nov.

Fig. 7

Diagnosis.

Pseudobaeospora deceptiva differs from P. pillodii by larger basidiospores, tetrasporic basidia and lack of rhizoids and from the other members of the genus by its unique phylogenetic position.

Etymology.

the species epithet derives from the Latin word deceptivus (= misleading) and refers to its strong resemblance to P. pillodii .

Holotype (here designated).

ITALY • Abruzzo, Ponte di Platano (CH), on the ground, on rotting leaves of Alnus alnobetula [= A. viridis (Chaix) DC. ], 28 August 2000, leg. et det. G. Robich, as P. pillodii ( MCVE: 15315) .

Description.

Habit collybioid. Pileus 5–20 mm broad, conical campanulate to plano-convex, expanding plane with an obtuse umbo, margin at first slightly crenulated-undulate, not striate, flattened to revolute in mature specimens, surface dry, pruinose to minutely felted, not or only slightly hygrophanous, dark violaceous (Dark Bluish Violet, Blackish Violet, Plate X; Navy Blue, Plate XXI; Dusky Violet-Blue 1, Plate XXIII), with a whitish paler margin. Lamellae deeply emarginate with slightly decurrent tooth to almost free, spaced, L = 18–20, 1 = (1 –) 3–5 (– 7), rather thick, narrow to ventricose, 1.5–2 mm broad, purple-lilaceous (Pale Amparo Purple, Light Amparo Purple, Plate XI; Light Mallow Purple, Mallow Purple, Plate XII; Pale Vinaceous, Plate XXVII), with a concolorous, entire to slightly irregular / eroded edge. Stipe 40–60 × 1.5–2.5 mm, cylindrical, flexuous, solid to slightly hollow at maturity, not filiform, concolorous with the pileus, at first sparsely but entirely covered by minute silky whitish fibrils and flocks, then evidently fibrillose only at apex (Fig. 7 a ), base radially strigose. Context violaceous. Pileus surface showing a negative reaction with a drop of 5 % KOH. Smell indistinct. Taste mild. Spore-print white.

Spores (3.9 –) 4.2–4.6 – 5.0 (– 5.4) × (2.6 –) 3.1–3.4 – 3.8 (– 4.1) µm (64 / 2 / 2), Q = (1.18 –) 1.25–1.36 – 1.46 (– 1.63), V = (15.4 –) 20.9–28.9 – 36.8 (– 46.5) μm 3, broadly ellipsoid to ellipsoid, colorless, smooth, in L 4; contents granulose or with one or two oil-droplets (guttules), at first thin-walled and inamyloid, but maturing after liberation and becoming thick-walled up to 0.8 µm, dextrinoid, congophilous and cyanophilous; hilar appendix prominent, 0.8–1 µm long (Fig. 7 e ). Basidia 15–19 × 6–7 µm, clavate, tetrasporic, with sterigmata up to 3 µm long. Hymenophoral trama regular to subregular, consisting of hyphae up to 8 µm wide, colorless in L 4. Hymenial cystidia not observed. Pileipellis: slightly gelatinized, a cutis composed of loose, 2.5–4 µm wide hyphae; hyphal terminations towards the pileus margin often ascending and arranged in subtrichodermic patches, subcylindrical, smooth, apically rounded, up to 8 µm wide; subpellis consisting of up to 8 µm wide cylindrical hyphae (Fig. 7 b – d ). Pigment brownish, intracellular. Stipitipellis consisting of 3–7 µm wide, non-dextrinoid parallel-oriented cylindrical hyphae. Stipititrama similar to stipitipellis structure but hyphae up to 10 wide. Caulocystidia present (observed at stipe apex), 10–40 × 5–10 µm, usually in tufts, thin-walled, colorless, often irregularly shaped, clavate, lageniform, sinuous, lobed, sometimes catenulated, with rounded apex (Fig. 7 f ). Clamp-connections absent in all parts.

Habitat and distribution.

Terrestrial, so far known only from Italy.

Additional specimen examined.

ITALY • Piemonte, Val d’Otro, Alagna Valsesia (VC), 10 September 1994, leg. et det. P. G. Jamoni, as P. pillodii ( MCVE: 4905) .

Notes.

Pseudobaeospora deceptiva is a species difficult to distinguish from P. pillodii without careful observation of some morphological characters: it shows larger basidiomes (pileus 5–20 mm and stipe up to 2.5 mm wide), a stipe without basal rhizoids, spores on average longer than 4.5 µm, and frequent subtrichodermic structures near the pileus margin. The two collections studied here were previously identified as P. pillodii . The difference between the spore dimensions of the two species is even more worthy of attention if we consider that while the collections of P. pillodii show a variable percentage of bisporic basidia, those of P. deceptiva are consistently tetrasporic. The ITS sequences do not unambiguously separate the two species (Fig. 3 ) but they are clearly different in the multigene analysis where also their SSU and LSU sequences are present (Fig. 2 ).

Pseudobaeospora sp. described in Adamčík and Ripková (2004 b) shares with P. deceptiva the colours of the basidiomes, the clamp-less hyphae, spores longer than 4 µm in average and a suprapellis containing numerous ascending to erect terminal elements (pileocystidia according to Bas 2003) but is distinguished by a very minute basidiome (pileus 4.5 mm wide and stipe 20 × 0.6 mm), pileus with 1–1.5 mm long marginal striation, very sparse lamellae (L = 11, l = 0–1), well-developed versiform to irregular cheilocystidia, different length / width spore ratio (Q = 1.08–1.29), bisporic basidia, and a pseudoparenchymatic subpellis of 9–24 µm wide hyphae.

Among the extra European clamp-less species, P. defibulata Singer described from Argentina on rotten leaves of dicotyledonous trees differs by a smaller pileus (3–7 mm wide), a thinner stipe (0.2–0.6 mm thick), a pale livid to partly almost white pileus, sparse lamellae (L = 13, l = 1), smaller spores, 4.0–4.2 × 3.0–3.2 µm, and a suprapellis of only horizontal hyphae ( Singer 1963). Pseudobaeospora citrina Rawla from India, is distinguished by small basidiomes (pileus 5–10 mm, stipe 10–15 × 1 mm) greenish yellow to citrine, pileipellis a trichoderm of repent up to 7 µm wide hyphae, with fasciculate, slightly thick-walled, 28–140 × 3–5 µm hairs (pileocystidia) ( Rawla and Arya 1991; Bas 2003).

Figures

Figure 2. Mid-point rooted Bayesian phylogeny (nrITS, nrLSU, nrSSU, RPB 2 - exons) of the Tricholomataceae s. s. Nodes were annotated with Bayesian PP (left) and ML BP (right) values, with the significance threshold considered as Bayesian PP ≥ 0.95 and / or ML BP ≥ 70 %. Subsignificant support values were annotated in parentheses. Boldface names represent samples sequenced for this study.

Figure 3. Bayesian inference phylogram built with ITS nucleotide sequence of Pseudobaeospora, rooted with Tricholoma inamoenum (Tricholomataceae) as outgroup. Nodes were annotated with Bayesian PP (left) and ML BP (right) values, with the significance threshold considered as Bayesian PP ≥ 0.95 and / or ML BP ≥ 70 %. Subsignificant support values were annotated in parentheses. Boldface names represent samples sequenced for this study. Clades are named following Craig et al. (2023).

Figure 7. Pseudobaeospora deceptiva (MCVE: 15315, holotype). a Basidiomes; b – d pileipellis; e spores; f caulocystidia; b – f in ammoniacal Congo red. Scale bars: 20 µm (b – d); 5 µm (e); 10 µm (f). Photos by L. Setti.