Russula inflata Buyck

Manz, Cathrin, Amalfi, Mario, Buyck, Bart, Hampe, Felix, Yorou, Nourou S., Adamčík, Slavomír & Piepenbring, Meike, 2025, Just the tip of the iceberg: uncovering a hyperdiverse clade of African Russula (Basidiomycota, Russulales, Russulaceae) species with signs of evolutionary habitat adaptations, IMA Fungus 16, pp. e 140321-e 140321 : e140321-

Russula inflata Buyck , Bull. Jard. Bot. Natl. Belg. 58 (3–4): 470 (1988)

Figs 24 , 25 , 26 , 27 , 28

Holotype.

DRC. Kisangani; NNE van Batiabongena , primary rainforest under Gilbertiodendron dewevrei (De Wild.) J. Léonard , 05. 05. 1984, leg. B. Buyck, 1652 (holotype of R. inflata, BR 5020005254166) .

Synonym.

Russula intricata Buyck , Bulletin du Jardin Botanique National de Belgique 58 (3–4): 470 (1988). Holotype – DRC. Luiswishi , dense forest, on ground, 20. 04. 1986, leg. J. Schreurs, 1778 ( BR 5020005258201 ).

Additional material examined.

Benin. Atakora, Natitingou, Kota Waterfalls , co-ord. 10°12.7'N, 1°26.8'E, alt. 500 m, in a gallery forest, under Uapaca guineensis , directly along the riverside on bare sand, 14. 07. 2021, leg. C. Manz, F. Hampe, N. S. Yorou, G. Abohoumbo & D. Dongnima, CM-21-128 ( B 70 0105431 , UNIPAR) ; ibid. 19. 07. 2021, CM-21-144 ( B 70 0105432 , UNIPAR) ; ibid. Kossoucoingou , co-ord. 10°9.5'N, 1°9.5'E, alt. 330 m, savannah woodland with dense undergrowth, under Uapaca sp. , on rocky soil, 27. 06. 2022, leg. C. Manz, S. Sarawi, A. Rühl, CM-22-231 ( B 70 0105433 , UNIPAR) . DRC. Luiswishi , at the margin of a gallery forest, at the foot of an abandoned termite mound, 1990, leg. J. Degreef, 90 / 9 (as R. roseoalba , BR 5020005039923 ) ; ibid. South of firm Kimba , 18. 04. 1986, leg. J. Schreurs, 1738 (as R. roseoalba , BR 5020006035214 ) ; ibid. 19. 03. 1986, leg. J. Schreurs, 1415 (as R. roseoalba , BR 5020006037232 ) ; ibid. Muhulu de la Luiswishi , dense dry forest, 27. 12. 1971, leg. D. Thoen, 5209 (as R. roseoalba , BR 5020006031179 ) ; ibid. Kisangani; NNE van Batiabongena , primary rainforest under G. dewevrei , 05. 05. 1984, leg. B. Buyck, 1653 ( BR 5020005255170 ) ; ibid. primary rainforest with G. dewevrei and Scaphopetalum Mast. , 05. 05. 1984, leg. B. Buyck, 1560 ( BR 5020005256184 ) . Senegal. Basse Casamance National Park , Guinean forest, 24. 08. 1986, leg. D. Thoen, 7647 (as R. roseoalba , BR 5020006032183 ) .

Short description.

Basidiomata small to medium-sized, pileus surface pinkish, stipe with fugitive annulus, hyphal terminations in the pileipellis of two types including presence of distinctly thick-walled, sparsely septate, very long hyphae repent over other elements of the suprapellis, occurring in gallery forests and savannah woodlands.

Description based on recent material from Benin.

Growth habit: solitary or gregarious. Pileus: small to medium-sized, 23–62 mm in diam., when young, convex, later expanding plane, centrally slightly to distinctly depressed; margin even or slightly involuted, distinctly tuberculate-striate up to 17 mm, crenulate, sometimes undulate or radially cracked; cuticle smooth, matt, sometimes with velar patches, distinctly radially cracked between the striations, sometimes easily and sometimes hardly peelable, colour near the margin pinkish-white (11–13 A 2), rose (11–12 A 3) or greyish-magenta (13 B 3, 13 D 3), near the centre, pinkish-white (11–12 A 2), dull red (11 B 3), greyish-ruby (12 C 4, 12 D 3–4), greyish-rose (12 B 4), but also yellowish-white (3 A 2). Lamellae: 3–4 mm wide, 4–8 lamellae present along 1 cm near the pileus margin, adnexed, white, furcations occasional near the stipe attachment, anastomoses and lamellulae absent; edges entire, concolourous. Stipe: 28–50 × 4–13 mm, cylindrical, sometimes clavate, smooth to slightly rugose, with a fugitive, white or rose (11 A 3) rimmed annulus that is sometimes attached to the pileus margin instead of the stipe, white or with a slight pinkish hue; cottony stuffed, with age becoming hollow. Context: up to 1 mm thick at half pileus radius, white, unchanging when bruised, brittle, taste mild, odour inconspicuous, macrochemical reactions: guaiac after 8–10 seconds weakly positive (+) or negative (-) on stipe and positive (++) on lamellae surfaces, FeSO 4 weak orange or pinkish, sulphovanillin negative, KOH discolouring yellowish on red cuticle parts, phenol negative. Spore print: not observed, but probably white or cream.

Spores: (6.9 –) 7.3–7.7 – 8.1 (– 8.9) × (6.6 –) 7–7.3 – 7.7 (– 8.4) µm (n = 90), Q = (1 –) 1.02–1.05 – 1.08 (– 1.13), globose to subglobose; ornamentation of distant to moderately distant amyloid warts [(2 –) 3–5 (– 7) in a circle of 3 µm diam.], 1–1.4 µm high, connected by abundant lines [(2 –) 3–5 (– 6) in the circle] forming a complete reticulum, isolated warts or fusions dispersed (up to 1 in the circle), lines frequently rimmed by additional smaller warts only visible by SEM; suprahilar plage small, inamyloid, without ornamentation. Basidia: (30 –) 34.5–39.5 – 45 (– 52) × (10.5 –) 11.5–12.5 – 13.5 (– 15.5) µm (n = 60), cylindrical, clavate to broadly clavate, 4 - spored; basidiola approx. 5–11 µm wide, cylindrical to subclavate. Hymenial cystidia: on lamellae sides (58 –) 65–72.5 – 80 (– 91) × (7 –) 9–11 – 13 (– 17) µm (n = 60), widely dispersed, 65–90 / mm 2, predominantly fusiform, rarely subclavate, sometimes slightly curved near the base, originating in subhymenium and somewhat protruding over basidia, thin-walled, apically acute, with a 2–10 (– 13) µm long appendage; heteromorphous contents dense, amorphous to crystalline, sometimes located only in the upper half, turning moderately, but distinctly greyish-black in sulphovanillin after 5–10 minutes. Hymenial cystidia near the lamellae edges shorter and narrower, (34 –) 41–46 – 51 (– 58) × (6 –) 7.5–9.5 – 11.5 (– 15) µm (n = 60), cylindrical to clavate, apically obtuse, without appendages, heteromorphous contents similar to those in hymenial cystidia on lamellae sides, but not crystalline. Lamellae edges: sterile, densely covered with marginal cells. Marginal cells: (19 –) 23–27 – 31 (– 36.5) × (6 –) 7–9 – 11.5 (– 15) µm (n = 60), fusiform or lageniform, acute or with a narrow appendage, frequently with a secondary septum, optically empty, thin-walled. Pileipellis: orthochromatic in Cresyl blue, sharply delimited from the underlying context, 65–120 µm deep; suprapellis a trichoderm, 30–70 µm deep, composed of predominantly erect, loose hyphal terminations embedded in a gelatinous matrix; gradually passing to a 25–50 µm deep subpellis, of dense, more or less parallel, not gelatinised, thin-walled, 4.5–9 µm wide hyphae with capitate and frequently forked terminations, not gelatinised. Acid resistant encrustations absent. Hyphal terminations: near the pileus margin dimorphic; mainly thin-walled, up to 50 µm long, composed of 1–2 (– 3) unbranched cells, terminal cells (9 –) 12.5–18.5 – 24.5 (– 31) × (2.5 –) 3.5–4.5 – 5 – (– 7) µm (n = 93), predominantly subulate with obtuse apex, less frequently cylindrical; subterminal cells shorter, 3.5–7 µm wide, cylindrical or ellipsoid; additionally mixed with dispersed, thick-walled, sparsely septate, filamentous, curved or bent, repent, up to 200 µm long hyphal terminations. Hyphal terminations near the pileus centre composed of equally represented thin and thick-walled forms, thin walled composed of (1 –) 2–3 unbranched cells, terminal cells (7 –) 9–16.5 – 24 (– 37) × (2.5 –) 3.5–4 – 5 (– 6.5) µm (n = 93), stout, cylindrical; subterminal cells similar, 3–6.5 µm wide; thick-walled ones similar to those near the pileus margin. Pileocystidia: near the pileus margin (15 –) 17–19.5 – 22.5 (– 26) × (3 –) 3.5–4 – 5 (– 6.5) µm (n = 60), one-celled, predominantly fusiform, sometimes subcylindrical, rarely curved, originating in the suprapellis, thin-walled, apically obtuse, with a 1–3 µm long terminal knob; heteromorphous contents amorphous, not reacting to sulphovanillin. Pileocystidia near the pileus centre longer, more abundant, (11.5 –) 18–26.5 – 35 (– 48) × (2.5 –) 3.5–4.5 – 5 (– 7) µm (n = 60), shape and heteromorphous contents similar to those in pileocystidia near the pileus margin. Context: without cystidioid and oleiferous hyphae.

Distribution and ecology.

Widely distributed in rainforests, gallery forests and savannah woodlands in tropical Africa. Associated with Asteropeia mcphersonii G. E. Schatz, M. Lowry & A. - E. Wolf , Gilbertiodendron dewevrei and Uapaca spp. Known from Benin, Cameroon, DRC, Gabon, Madagascar and Senegal.

Notes.

Russula inflata is the type species of the subsect. Inflatinae defined by a pileipellis composed of a dense layer of intricate hyphae with irregular orientation and frequently inflated hyphal terminations ( Buyck 1994). Based on this pileipellis morphology, R. intricata and R. roseoalba were also placed in this subsection. Sequences (ITS) of both type specimens are available as a result of this study. Since phylogenetic and morphological differences are minor, we consider R. intricata as a synonym of R. inflata . The sequence variation of the R. inflata clade in the ITS phylogeny might be caused by intraspecific / intragenomic polymorphisms which seem rather common in fungi ( Cedeño-Sanchez et al. 2024). Our observations proved that the species is morphologically more variable than previously thought, which explains why two different morphotypes of this species were described in the same publication as different species. The spore ornamentation is also variable and was up to 1.5 µm high in Benin material or up to 2.5 µm high in type material of R. inflata . We also observed variable marginal cells which were unbranched with secondary septa in material from Benin, rarely branched in type material of R. intricata or frequently branched in type material of R. inflata . The shape of the terminal cells in the pileipellis is distinctly different between the pileus centre and margin. The presence of thick-walled inflated hyphal terminations in the subpellis was underlined in the original description of R. inflata , but according to our observations, it is not a reliable character for the species identification because these elements can sometimes be thin-walled, subcapitate and not distinctly inflated. To understand these variations in morphology and sequence polymorphisms, sampling covering the entire ecological and geographical range of the lineage and providing better quality for performing a multi-loci analysis is essential. Russula roseoalba is a species with similar field appearance due to which it was frequently confused with R. inflata and, because of that, several collections identified as this species by Buyck (1994) had ITS sequences matching R. inflata . Russula roseoalba can be distinguished by the absence of the striking thick-walled, up to 200 µm long pileipellis hyphae.

Figures

Figure 24. Russula inflata A – C field pictures of basidiomata: A CM- 21-144, B CM- 22-231, C CM- 21-128, D scanning electron microscopical picture of basidiospores (CM- 21-144). Scale bar: 1 cm (A, C); 2 cm (B); 3 µm (D).

Figure 25. Hymenial elements of Russula inflata (CM- 21-144) A basidia and basidiola, B hymenial cystidia near the lamellar edges, C marginal cells, D hymenial cystidia, E spores as seen in Melzer’s reagent. Scale bar: 10 μm, but only 5 μm for spores.

Figure 26. Elements of the pileipellis near the pileus centre of Russula inflata (CM- 21-144) A pileocystidia, B hyphal terminations, C thick-walled hyphal terminations. Scale bar: 10 µm.

Figure 27. Elements of the pileipellis near the pileus margin of Russula inflata (CM- 21-144) A pileocystidia, B hyphal terminations, C thick-walled hyphal terminations. Scale bar: 10 µm.

Figure 28. Russula inflata (CM- 21-144). Hyphal terminations of the subpellis. Scale bar: 10 µm.