Russula Delica Descriptive Essay

Russula alatoreticula K. Acharya, S. Khatua, A.K. Dutta & S. Paloi, sp. nov.

MycoBank. MB 814640.

Etymology. ‘alatoreticula’ is the Latin transliteration of English, winged little nets, for the typical reticulate-winged ornamentation of the basidiospore.

Holotype. India, West Bengal, West Midnapur district, Gurguripal, 22°25'49.13" N, 87°12'57.26" E, alt. 45 m, S. Paloi, 22 August 2013, CAL-1271.

Diagnostic description.

Basidiomycota: Russulales: Russulaceae. Medium-sized (40–50 mm), plano-convex to finally infundibuliform, pastel red to dull red or greyish red pileus that turns reddish-orange with KOH; white lamellae turning yellowish-orange with KOH, absence of lamellulae; entirely white stipe; white spore print; mild taste; globose to subglobose (6.5–7.5 × 5.4–7.2 μm; Q = 1.1) basidiospores, with nearly complete reticulum to reticulate-winged ornamentation, amyloid suprahilar spot; presence of hymenial cystidia shaped clavate to subclavate with capitates to moniliform apex on gill sides (60–68 × 10.5–11.5 μm) and edges (43–50 × 10–11 μm); and presence of narrow (3–4 μm) caulocystidia.

Pileus 40–50 mm diam., at first convex, becoming plano-convex with a depressed centre, then infundibuliform with maturity (Fig 1A); surface smooth, pastel red (9A5) to dull red (10B4) or greyish red (10B5), often rose pale red (11A4), centre red (9A6-7; 9B7) to reddish brown (9D7-8), no colour change on exposure or with NH4OH, turns reddish-orange orange with KOH, scarlet red with FeSO4; margin reflexed at maturity, moderately striate towards margin; context 2 mm thick, white, translucent with NH4OH, turns yellowish-orange to 9H with KOH and fulvous with FeSO4. Lamellae adnexed, 4 mm broad, subdistatnt (spacing ca. 1 mm at pileus margin) after maturity, regular, white (1A1), unchanging after bruising, turning yellowish-orange with KOH, fulvous with FeSO4 and orange with sulphovanillin; edge concolorous; lamellulae absent. Stipe 31 × 10 mm, central, straight, cylindric with tapered at base, smooth, white (1A1), moist. Context solid in stipe, white (1A1), unchanging after bruising, apricot with FeSO4 which later turns into light snuff brown, no colour change with guaiac and phenol, orangish with KOH. Taste mild. Odour indistinctive. Spore print white.

Fig 1. Russula alatoreticula (CAL-1271).

(A) Fresh Basidiomata in the field. (B-C) Habitat—Shorea robusta dominated areas of Gurguripal and Khairulachak, West Bengal from where basidiomata of Russula alatoreticula were collected (photographs by S. Paloi). Scale bars: 10 mm in A.

https://doi.org/10.1371/journal.pone.0178050.g001

Basidiospore globose to sub-globose, (6.5–)6.8–7.0–7.2(–7.5) × 5.4–6.2–6.3(–7.2) μm, Q = 1.05–1.1–1.2, ornamentation composed of very high (1.3–2.1 μm high) ridges with crenulated to irregularly interrupted margin that are aligned or connected to give nearly complete reticulum to reticulate-winged fashion (Fig 2A and 2B), amyloid; suprahilar spot amyloid. Basidia (39–)40–45(–49) × 10.8–11.6(–12.5) μm, 4–spored, clavate to sub-clavate, oil-granule present when viewed with KOH, thin walled; sterigmata 4–5.5 × 1.5–2 μm (Fig 2C). Subhymenium pseudoparenchymatic. Lamellar trama composed of 33–39 × 25–34 μm, isodiametric, hyaline nested sphaerocytes. Hymenial cystidia ca. 60–65(–68) × 10.5–11.5 μm on gill sides (Fig 2D), near gill edge ca. 43–50 × 10–11 μm, clavate to subclavate with capitates to moniliform apex, thin-walled, oil granule present when viewed with KOH. Pileipellis sharply delimited from underlying sphaerocytes of the context, distinctly two layered (Fig 2E and 2F); subpellis (39–)42–54(–57) μm dense, rather gelatinized, composed of horizontally oriented hyphae that are ca. 3.5–5.5 μm wide; suprapellis less gelatinized, (28–)43–46(–50) μm deep, composed of ca. 3.5 μm broad hyphae with pyriform to subulate endings. Incrustations absent. Stipitipellis composed of hyaline, septate hyphal cells. Caulocystidia present, 3–3.5(–4) μm broad, narrow. Clamp-connections absent in all parts.

Fig 2. Microscopic features of Russula alatoreticula (CAL-1271, holotype).

(A-B) Scanning Electron Micrograph of basidiospores. (C) Basidia. (D) Hymenial cystidia (gill sides) as observed in Congo red. (E) Pileipellis. (F) Sphaerocytes. Scale bars: 10 μm in C-F.

https://doi.org/10.1371/journal.pone.0178050.g002

Habit and habitat. solitary, common, growing under Shorea robusta C.F. Gaertn. tree in the lateritic regions of West Bengal (Fig 1B and 1C).

Additional specimen(s) examined. India, West Bengal, Birbhum district, Shantiniketan, 23°40ʹ57ʹʹ N, 87°40ʹ24ʹʹ E, alt. 67 m, P. Mitra, 21 July 2012, CUH AM112; West Midnapur district, near Khairulachak, 22°27'1.94" N, 87°14'49.32" E, alt. 67 m, 24 July 2012, S. Paloi, CUH AM113; Durgapur, 30 August 2013, P. Mitra, CUH AM 114.

Note. Both the macro- and micro-morphological characters (see diagnosis), as well as full support for its phylogenetic placement (PP = 1.00; Fig 3) together with R. aurea, the type species of the subsect. Aurantinae, undoubtedly place the present taxon under the subsect. Aurantinae, of sect. Polychromae, of the subgen. Russula [42].

Fig 3. Phylogenetic tree.

Consensus phylogram (50% majority rule) resulting from a Bayesian analysis of the nrITS sequence alignment of Russula species, showing mean branch lengths, obtained from 106 generations of an MCMC analysis. Bayesian posterior probabilities (≥ 0.50) has been indicated above the branches. The scale bar represents number of expected changes per site. Categorizations of Russula species within the phylogenetic tree follows classification of Sarnari [42].

https://doi.org/10.1371/journal.pone.0178050.g003

Within the same subsect. Aurantinae, the present species appears close to Russula aurea Pers. but, easily distinguish from the later by its smaller size of the basidiospores (6.5–7.5 × 5.4–7.2 μm), very distinct (reticulate-winged up to 2.1 μm high) and unique (in this group) spore ornamentation. In addition, the occurrence of the new species concerned in tropical region and in association with Shorea robusta is very striking. In the Indian context, under subgen. Russula, among species with more or less same colouration of pileus and smaller size of the basidiospores: Russula rosea Pers. differs by the presence of light yellow to pale orange yellow coloured lamellae, pale yellow spore print, and fertile lamellae edge [43,44]; Russula minutula var. robusta Saini, Atri & Singer has forked lamellae with red coloured margin, and a spore ornamentation that is more typical of subsect. Roseinae (partial reticulum or warts connected by veins); Russula xerampelina differs by the presence of forked lamellae, white tinged with vinaceous red coloured stipe which turns brown at maturity, ochraceous yellow coloured spore print and basidiospores ornamentation composed of conic to spinoid isolated warts [44]. Among other species belonging to the subgen. Russula with white coloured spore print, R. emetica (Schaeff.) Pers., previously reported to be common in temperate mixed forest of India, differs by its acrid taste, having lamellae forked near the stipe, presence of lamellulae, slightly different size (7.4‒9.8 × 6‒7 μm; Q = 1.14‒1.46) basidiospores, and presence of cylindrical subclavate to clavate pileocystidia [44]; Russula vaurasiana K. Das & J.R. Sharma, originally described from India [44], differs by having a pileus coloured deep yellowish pink to reddish orange with light orange yellow tinge towards centre, forked and interveined lamellae, presence of cylindrical to subclavate pileocystidia, and distinctly broader basidiospores (7.3‒9.8 × 6.2‒8 μm).

Among phylogenetically related species: Russula melliolens differs by cream coloured spore-print and distinctly broader size basidiospores (9‒11 × 7.7‒9.8 μm) [45]; R. gracillima Jul. Schäff. has purple to dark vinaceous or violaceous pileus, yellowish white to saffron luteous spore print, cylindrical to clavate pileocystidia, and basidiospores ornamentation composed of mostly conic isolated warts [44]; Russula velenovskyi Melzer & Zvára, originally described from Czech Republic and subsequently reported to be common in Europe, differs by its ochraceous spore print, coarser acid-fast taste, obovate basidiospores, and presence of pileocystidia [46]; and R. integriformis differs by having brownish yellow coloured pileus, sweet taste, yellow spore print, and fusiform hymenial cystidia [47].

Russula delica is a mushroom that goes by the common name of milk-white brittlegill, and is a member of the Russula genus, all of which are collectively known as brittlegills. It is mostly white, with ochraceous or brownish cap markings, and a short robust stem. It is edible, but poor in taste, and grows in coniferous, broadleaved, or mixed woods. It can be confused with other white Russula species and certain white Lactarius species.

Taxonomy[edit]

First described by the Swedish mycologist Elias Magnus Fries in 1838, its specific epithetdelica is Latin for "weaned".[1] Older names include Christian Hendrik Persoon's Lactarius piperatus var. exsuccus.

This species has undergone many taxonomic changes over the years. Russula chloroides is now considered a distinct species because of the very dense lamellae and blue/green zone at the stem apex of some specimens.[2] Gill spacing, gill depth, spore colour and spore ornamentation have also thrown many finds into doubt, and a number of varieties have been described throughout the years.[3][4]

Mycologist John Burton Cleland collected a form he described in 1935 as R. delica from under eucalypts in the Mount Lofty Ranges in South Australia,[5] however, this was reclassified as a new species R. marangania in 1997 by Cheryl Grgurinovic.[6]

Description[edit]

The basidiocarps (fruiting bodies) of Russula delica seem loath to leave the soil, and are often found half buried, or sometimes growing hypogeously. As a result, the caps often trap the surrounding leaf debris and soil on their rough surfaces. The cap can be 16 cm (6.3 in) in diameter. It is white, usually tinged with ochre or brown, with an inrolled margin, which usually remains white. At first it is convex, but later flattens, and is often funnel shaped. The firm, white stipe is short and stout, measuring 2–6 cm (0.8–2.4 in) high and 2–4 cm (0.8–1.6 in) wide. The gills are decurrent, and are quite closely spaced initially. The spore print is creamy white, and the warty oval spores measure 8–12 x 7–9 μm. The flesh is white, and does not change colour on cutting. It has a pleasant, fruity smell when young, but at maturity it may develop a faintly fishy or unpleasant smell.[7] It has a spicy, tangy taste.[8]

Similar species[edit]

Russula chloroides is very similar and often confused with R. delica. It can be separated by the turquoise band at the apex (at the attachment of the gills with the cap) and by its unpleasant, peppery smell.

Russula pallidospora is another similar species, which has very tough flesh, more distant gills and an ochraceous spore deposit.

Russula flavispora is also similar but rare, and has dense gills and a deep ochraceous spore deposit.

Similar whitish milk-cap species, such as Lactifluus piperatus all exude milk from the gills, and the cut flesh.[9]

Distribution and habitat[edit]

Russula delica is widespread in the northern temperate zones, including Europe and Asia.[8] It is particularly common in the Eastern Mediterranean. It is a thermophylic species, appearing during hot spells in summer and autumn in broadleaved and coniferous woods.[8] In North America Russula delica is rare and is largely replaced by R. brevipes,[10] which is very similar, but not found in Europe.

Edibility[edit]

This mushroom is edible but poor, having an unpleasant taste,[8] leading some to classify it as inedible.[1] However, in Cyprus,[11] as well as certain Greek islands such as Lesvos,[12] huge numbers of Russula delica are collected and consumed every year. They are usually pickled and preserved in olive oil, vinegar or brine, after prolonged boiling.

See also[edit]

References[edit]

External links[edit]

  1. ^ abNilson S & Persson O (1977). Fungi of Northern Europe 2: Gill-Fungi. Penguin. p. 112. ISBN 0-14-063006-6. 
  2. ^"Russula chloroides". The Russulales News Team. 2007. 
  3. ^Sarnari, M. (1998). Monografia Illustrata del Genere Russula in Europa. Vol. 1. A.M.B. Fondazione.
  4. ^Galli, R. (2003). Le Russule 2nd Edition. R. Galli.
  5. ^Cleland JB (1976) [1935]. Toadstools and mushrooms and other larger fungi of South Australia. South Australian Government Printer. p. 150. 
  6. ^Bougher NL, Syme K (1998). Fungi of Southern Australia. Nedlands, WA: University of Western Australia Press. p. 148. ISBN 1-875560-80-7. 
  7. ^Loizides M, Kyriakou T, Tziakouris A. (2011). Edible & Toxic Fungi of Cyprus (in Greek and English). Published by the authors. pp. 250–51. ISBN 978-9963-7380-0-7.
  8. ^ abcdRoger Phillips (2006). Mushrooms. Pan MacMillan. pp. 45–46. ISBN 0-330-44237-6. 
  9. ^Haas, Hans (1969). The Young Specialist looks at Fungi. Burke. p. 74. ISBN 0-222-79409-7. 
  10. ^Arora D. (1986). Mushrooms Demystified. Ten Speed Press. p. 88. ISBN 0-89815-169-4. 
  11. ^Loizides, M. (2008). A secret world: The fungi of Cyprus. Field Mycology 9 (3): 107-109. DOI:10.1016/S1468-1641(10)60420-3.
  12. ^Μανιταρόφιλοι Λέσβου (2013). 100+1 Μανιτάρια: Η έρευνα στη Λέσβο [in greek]. 192 p. ISBN 978-618-80314-3-2.

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