Russula ferruginea Corrales & Vera, 2022

Buyck, Bart, Eyssartier, Guillaume, Armada, François, Corrales, Adriana, Hembrom, Manoj Emanuel, Rossi, Walter, Bellanger, Jean-Michel, Das, Kanad, Dima, Bálint & Ghosh, Aniket, 2022, Fungal biodiversity profiles 111 - 120, Cryptogamie, Mycologie 20 (2), pp. 23-61 : 43-44

118. Russula ferruginea Corrales & Vera , sp. nov.

( Figs 16A ; 17-20 )

DIAGNOSIS. — R. ferruginea sp. nov. differs from the European R. praetervisa Sarnari or the North American R. amerorecondita Avis & Barajas in the combination of the relatively delicate stature, dark brown pileus centre contrasting to its pale yellowish brown margin, almost mild taste and especially its conspicuous color change from light brown to reddish brown or rusty on wounded places especially apparent on the stipe base and the lamellae. It is defined also by combination of narrow hymenial cystidia up to 8 µm and spores with warts connected by fusions and short fine lines.

HOLOTYPE. — Colombia. Cundimarca Depart., Mosquera , Chicaque Natural Reserve , 4°36’22”N, 74°18’17”W, alt. 2130 m, in forest dominated by Quercus humboltii , terrestrial, 17.X.2019, A. Corrales 944 ( HUA, SAV ).

MYCOBANK. — MB841769.

GENBANK. — MZ604288 (ITS), MZ604283 (nrLSU), MZ553923 (rpb2), MZ553926 (tef1 α), all from holotype.

ETYMOLOGY. — The name refers to reddish spots on the base of the stipe and colour change of the wounded context from light brown to reddish brown, resembling iron rusting.

ADDITIONAL MATERIAL STUDIED. — Colombia. Cundimarca Depart., Mosquera, Chicaque Natural Reserve, 4°36’22”N, 74°18’17”W, alt. 2130 m, in forest dominated by Quercus humboltii , terrestrial, multiple collections of different mycelia distant approximately hundred meters apart, 17.X.2019, A. Corrales 914, A. Corrales 935, A. Corrales 1019 (all deposited in HUA ).

SPECIMENS STUDIED FOR COMPARISON. — Russula austromontana (Singer B 12402 (F), holotype); Russula cf. austromontana / crucensis : Costa Rica, 3.5 km W of Empalme, 2200 m asl., in montane Quercus seemannii forest, 2.VI.2001, leg. B. Buyck, BB 01.023 (PC); ± 5 km SW of Cerro de la Muerte, Albergue de la Montana, Savegre, 2200 m asl., in montane Quercus seemannii forest, 6.VI.2001, leg. B. Buyck, BB 01.076 (PC).

DESCRIPTION

Pileus

Small to medium sized, 24-48 mm in diam., when young convex, mature plane with depressed centre; margin strongly tuberculate-striate to c. half of the radius (7-13 mm); cuticle slimy especially near the center, shiny, margin peeling or radially cracking, color near margin light brown turning to light yellowish brown or beige, near the center dark brown, deep blackish brown to almost black, discoloring to yellowish brown.

Lamellae

Moderately distant, c. 8-12/ 1 cm near the pileus margin, 1.5-4 mm broad, pale yellowish-brownish to almost white, lamellulae rare, furcations frequent especially near the stipe, edge even and concolorous.

Stipe

28-33 × 5-7.4 mm, cylindrical and staight, longitudinally striate, light brown, darker and with reddish spots at the base, cortex 1-2 mm thick, interior cavernate.

Context

2-3 mm thick at the middle of the pileus radius, fragile, light brown, flesh turning reddish brown when cut and getting more red spots at the base when bruised, taste slightly bitter and spicy, odour fishy and fetid.

Spore print

Not observed.

Spores

(6.4-)6.8-7.5-8.1(-8.6) × (5.4-)5.7-6.2-6.7(-7) µm, subglobose to broadly ellipsoid Q = (1.07-)1.13-1.21-1.28(-1.34); ornamentation of moderately large, moderately distant [(4- 7(-8) in a 3 µm diam. circle] amyloid, obtuse warts, (0.3)0.4- 0.8(-1) µm high, mainly fused in small groups or short chains ([0-]1-4[-5] fusions in the circle), connected by occasional and usually short line connections ([0-]1-3[-5] in the circle); suprahilar spot not amyloid, relatively large, smooth or covered by few small low warts.

Basidia

(22-)35-43.7-53 × (5.5-)7-9.2-11(-12) µm, narrowly clavate, ocassionally pedunculate, 4-spored; basidiola cylindrical or clavate, c. 5-9 µm wide.

Hymenial cystidia

Mostly numerous, c. 1800-2100/mm2, (50-)56-67.8-79(- 86) × 6-7.1-8(-9) µm, mainly fusiform or lancelolate, rarely narrowly langeniform or subcylindrical, apically mainly acute and sometimes pointed, occasionally obtuse, often moniliform, mainly with small, pearl-like, 1-3(-6) µm long appendage, thin-walled; contents weakly heteroformous, with fine, dispersed granulations usually near the apex, sometimes optically empty, often in Congo red with pale yellow pigment, turning almost black in sulfovanillin; near the lamellae edges smaller, (35-)38-48.4-58(-66) × 6-6.8-8µm, similar in shape and contents.

Marginal cells

Similar to basidiola but smaller, (12-)14-17-20(-21) × 5-6.5- 7.5 µm, cilindrical or clavate, apically obtuse, mixed with occasional basidia.

Pileipellis

Orthochromatic in Cresyl Blue, sharply delimited from the underlying context, 150-240 µm deep; suprapellis strongly gelatinized, verrucose-bumpy in vertical section, irregularly 15-35 µm deep, composed of more or less repent, loose or clustered hyphae; gradually passing to 120-220 µm thick subpellis formed by loose, gelatinised, irregularly oriented but near trama horizontally oriented, dense, 2-4 µm wide hyphae.

Acid-resistant incrustations

Absent.

Hyphal terminations

Near the pileus margin composed mainly of one or two cells, flexuous,thin walled, frequently branched, occasionaly nodulose or angulose; terminal cells (9-)12.5-19.7-27(-34) × 2.5-3.8-5(- 5.5) µm, mainly cylindrical or clavate, often apically obtuse and sometimes slightly narrowed; subterminal cells usually as wide as long, frequently branched or with lateral projections.Hyphal terminations near the pileus centre similar, (12-)14-23.8-33(- 41) × 3-4.3-5(-6) µm, more frequently angulose-nodulose.

Pileocystidia

Near the pileus margin always 1-celled, subulate, narrowly fusiform or lancelolate, variable in length and often long and originating deep in the subpellis, thin-walled, (24-)29-40.4- 51(-76) × 3-4.2-5 µm, apically mainly acute, with a small appendage or knob; contents dispersed, finely granulous, weakly greying in sulfovanillin. Pileocystidia near the pileus centre similar in shape but usually shorter (22-)28-36.6- 42.5(-47) × (3-)3.6-4.4-5.2(-6.5) µm, more frequently apically constricted than acute, with contents located in diverse places, usually in apical parts.

Cystidioid hyphae

Dispersed in subpellis but more frequent near the context, sometimes similar to cystidia but longer, contents often more conspicuous, oleipherous and turning dark brown in sulfovanillin and red after carbolfuchsin treatment.

Clamp connections

Absent from all tissues.

NOTES

The multilocus phylogenetic reconstruction based on nrLSU, rpb2 and tef1 α ( Fig. 5 ) clearly places our Colombian and Panamanian collections in one monophyletic clade with strong support values concerning bootstrap (MLbs = 100 %) and Bayesian posterior probability (BPP = 1). This clade is recognised in this study on the rank of species as R. ferruginea sp. nov. It belongs to section Ingratae Quél. of the subgenus Heterophyllidinae Romagn. The rusty-spotted North American R. pulverulenta Peck is the sister species of R. ferruginea sp. nov. (MLbs = 61 %, BPP = 0.96), although with poor support. The collection BPL276, labelled as R. pectinatoides Peck , is placed on the higher rank node with moderate support (ML = 68, BI = 0.96). In the ITS analyses (see sample with GenBank accession number KT 933975 in Fig. 6 ), however, this collection forms part of the species clade of R. amerorecondita .

Because sequence data are not yet available for many species of the section Ingratae , our multilocus analysis is undersampled. To trace close relationships and to eliminate coidentity with some taxa published earlier, we analysed also the ITS region based on a set of sequences ( Fig. 6 ) representing the described diversity of American species of the section Ingratae . The topology of this tree is not consistent with the topology obtained in the multilocus analyses and good bootstrap support is usually limited to terminal nodes. Russula ferruginea sp. nov. is placed in a strongly supported clade on a long branch, but there is no support for a more precise placement within the section Ingratae . Colombian and Panamanian collections of the new species received good support (MLbs = 97% and MLbs = 94 % respectively), but they are recognised on the rank of subspecies as discussed below (see comment under subsp. panamensis ).

The field appearance of R. ferruginea sp. nov. with a relatively fragile stature, dark brown pileus centre contrasting to its pale yellowish brown margin and almost mild taste resembles the European species R. praetervisa or the North American R. amerorecondita . A remarkable feature of R. ferruginea sp. nov. is its conspicuous color change, of the trama becoming reddish brown or rusty on wounded places, especially apparent at the base of the stipe and at the lamellae. This distinct rusty aspect of bruised surfaces is known in several other species of Ingratae such as R. illota Romagn. or R. pulverulenta . With different intensity, however, this color change also occurs in many other species of Ingratae .

Among the 78 Russula species described from Latin America ( Vera et al. 2021), only some are known from subtropical and tropical montane oak forests and, among these, four are described from Costa Rica as members of the section Ingratae : R. arcyospora Singer , R. austromontan a Singer, R. crucensis Gómez and Alfaro and R. quercusoleoideis Singer et al. Russula arcyospora is similar to R. foetens Romagn. but has odour components of bitter almond and a prominent spore ornamentation composed of high ridges ( Singer 1990). Russula austromontana ( Singer 1989) is similar to R. ferruginea sp. nov., but has broader hymenial cystidia and more prominent spore ornamentation composed of mostly isolated warts, according to our personal (BB) observations of the type. We sequenced two recent collections collected at or near the type locality in Costa Rica with macroscopical and microscopical characteristics similar to the type collection of R. austromontana . These specimens proved to be unrelated to R. ferruginea sp. nov. in our phylogeny. Russula crucensis , originally classified in sect. Pellicullariae R. Heim subsect. Discopodinae R. Heim , is another member of the section Ingratae ( Buyck 1992) and differs from R. ferruginea sp. nov. exactly in the same features as R. austromontana , from which it is difficult to distinguish at this moment. R. quercusoleoideis was originally placed in sect. Ingratae ( Singer et al. 1983), but according to Buyck (1992) it is a member of subsect. Griseinae Jul. Schäff. and both, pileipellis structure and hymenial cystidia, are different from the corresponding structures in R. ferruginea sp. nov.

Figures

FIG. 16. — Basidiomata of Russula ferruginea Corrales & Vera,sp. nov.A, basidiomata of Russula ferruginea subsp.ferruginea Corrales & Vera, subsp. nov. in the field (HUA Corrales935); B, C, basidiomata of Russula ferruginea subsp. panamensis Corrales & Vera,subsp. nov.in the field (ARIZ Corrales099); D, basidiomata of Russula ferruginea subsp. panamensis Corrales & Vera, subsp. nov. (UCH Anna Giessel A28). Scale bars: 1 cm.

FIG. 17. — Russula ferruginea subsp. ferruginea Corrales & Vera, subsp. nov. (HUA Corrales 944, holotype). Elements of the hymenium drawn as seen by light microscopy. A, basidia and basidiola; B, marginal cells near the edges of lamellae; C, basidiospores in Melzer’s reagent; D, hymenial cystidia near the edges of lamellae; E, hymenial cystidia on the sides of lamellae. Cystidia with contents as observed in Congo Red. Scale bars: A, B, D, E, 10 μm; C, 5 μm. Drawings by Michelle Vera.

FIG. 18. — Russula ferruginea subsp. ferruginea Corrales & Vera, subsp. nov. (HUA Corrales 944, holotype). Elements of the pileipellis drawn as seen by light microscopy. A, pileocystidia near the pileus margin; B, pileocystidia near the pileus center; C, hyphal terminations near the pileus margin; D, hyphal terminations near the pileus center. Cystidia with contents as observed in Congo Red. Scale bar: 10 μm. Drawings by Michelle Vera.

FIG. 19. — Maximum likelihood (ML) tree of Russula subgenus Heterophillidiae based on combined sequence data of nrLSU, rpb2 and tef1α. Bootstrap values from ML analysis ≥50% and Posterior probabilities from Bayesian inference (BPP) ≥0.95 are shown at branch nodes. The newly generated sequences of R. ferruginea sp. nov. are highlighted in boldface and on coloured background. Data of sequences used for the tree are listed in Table 2. Protocols for DNA extraction, PCR and sequencing followed Vera et al. (2021). Sequences were edited in the BioEdit 7.2.5 sequence alignment editor (Hall 2013) and Geneious R10 (Kearse et al. 2012). Intra-individual polymorphic sites having more than one signal were marked with NC-IUPAC ambiguity codes.The datasets were aligned in MAFFT 7 using the E-INS-i strategy (Katoh & Standley 2013) and manually improved in Geneious R10 (Kearse et al. 2012). Divergent and ambiguously aligned positions in the nrLSU were removed with Gblocks (Castresana 2000) using the least stringent parameters. Intronic positions of rpb2 and tef1α were manually removed. For the BI analysis, the data set was divided into five partitions: 28S, the 1st+2nd, and 3rd codon positions of tef1, the 1st+2nd, and 3rd codon positions of rpb2. The best substitution model for each partition was computed jointly in PartitionFinder 1.1.1 (Lanfear et al. 2012). BI runs were computed twice in MrBayes 3.2.6 (Ronquist et al. 2012) with four Markov chain Monte Carlo (MCMC) chains for 10 million iterations until the standard deviation of split frequencies fell below the 0.01 threshold. Convergence of runs was visually assessed using the trace function in Tracer 1.6 (Rambaut et al. 2013). For the ML analysis, the concatenated alignment was loaded as a fasta file to CIPRES Science Gateway (Miller et al. 2010) and analyzed using RAxML-HPC2 on XSEDE (8.2.12) as a partitioned data set (as in the BI analysis) under the GTR+GAMMA model with 1000 bootstrap iterations as recommended by the RAxML user manual (Stamatakis 2014).

FIG. 20. — Maximum likelihood tree of Russula sect. Ingratae based on sequence data of the ITS region. The newly generated sequences are in boldface, two subspecies of R. ferruginea sp. nov. are highlighted by different colour backgrounds. Names of taxa are followed by GenBank accession numbers and country of origin of samples, newly generated sequences are annotated with collection numbers. Protocols for DNA extraction, PCR and sequencing followed Vera et al. (2021). Sequences were edited in the BioEdit 7.2.5 sequence alignment editor (Hall 2013) and Geneious R10 (Kearse et al. 2012). The data set was analyzed on the CIPRES Science Gateway (Miller et al. 2010) under the GTR+GAMMA model with 1000 bootstrap iterations (Stamatakis 2014).

FIG. 5. — Entoloma nigroflavescens Armada, Bellanger, Noordel. & Dima, sp. nov., habit in situ (from holotype). Photo: F. Armada.

FIG. 6. — Microstructures of Entoloma nigroflavescens Armada, Bellanger, Noordel. & Dima, sp. nov.: A, spores; B, lamella edge with basidia and basidioles; C, D, elements of pileipellis. Photos: F. Armada. Scale bars: A, 10 µm; B, D, 20 µm; C, 50 µm.