Russula ochrobrunnea S.Y.Zhou, Y.Song & L.H.Qiu, 2020

Zhou, Songyan, Song, Yu, Chen, Kaixing, Li, Jingwei, Buyck, Bart & Qiu, Lihong, 2020, Three novel species of Russula Pers. subg. Compactae (Fr.) Bon from Dinghushan Biosphere Reserve in southern China, Cryptogamie, Mycologie 20 (14), pp. 219-234 : 232-233

Russula ochrobrunnea S.Y.Zhou, Y.Song & L.H.Qiu , sp. nov.

( Figs 7 ; 8 )

MYCOBANK NUMBER. — MB 835743.

HOLOTYPE. — China. Guangdong Province, Zhaoqing City, Dinghushan Biosphere Reserve , on the ground in broadleaf forest, 15.VII.2019, S. Y. Zhou K19071502 ( GDGM 79718 ).

ETYMOLOGY. — Named after its light brown lamellae with ochre margin when mature.

DIAGNOSIS. — Characterized by its grayish-brown pileus with striate to slightly cracking margin, sparse and light brown lamellae with ochre margin when mature, small basidiospores, presence of 1-spored basidia, flexuous to cylindrical hymenial cystidia often with papillate or branched apices and hyphae usually with brown pigments in pileipellis.

HABITAT AND DISTRIBUTION. — Solitary or gregarious in evergreen broadleaf forest.

ADDITIONAL SPECIMENS EXAMINED. — China. Guangdong Province, Zhaoqing City, Dinghushan Biosphere Reserve, on the ground in broadleaf forest, 2.VI.2018, S. Y. Zhou K18060208 (GDGM 79719).

DESCRIPTION

Basidiomata

Medium to large sized, agaricoid.

Pileus

7-9 cm in diameter, applanate with a depressed center to concave when mature; surface dry, not viscid, grayish-brown to tan, cracking into reticulum; margin slightly undulate or upward, striate.

Lamellae

Adnate to decurrent, distant (3-4 pieces of lamellae and lamellulae/cm at the margin of pileus), thick, firm, irregularly unequal; light brown to ochre; gill edge concolorous, but becoming tan to dark brown from drying out when old.

Stipe

4-6 × 2.4-3 cm, central to eccentric, cylindrical, mostly tapering downwards or slightly curving, solid, off-white.

Context

White, unchanging, 3-5 mm thick near stipe.

Odour

Unpleasant.

Taste

Not taken.

Spore print

White.

Basidiospores

Subglobose to ellipsoid, [40/2/2] (3.9-) 4.1-4.4-4.7 (-5.1) × (3.4-) 3.5-3.7-4.0 (-4.3) µm, Q = (1.09-) 1.10-1.18-1.29 (-1.30); ornamentations amyloid, composed of dense warts, some fused into ridges, forming a partial reticulum; suprahilar spot inamyloid.

Basidia

(24-) 26.5-32-39 (-42.5) × 4.5-6-7.5µm, clavate to cylindrical, 1-, 2-, 3- or 4-spored, hyaline or containing granular contents.

Lamellar trama

Composed of nested sphaerocytes surrounded by connective hyphae.

Pleurocystidia

(60.5-) 71-98-136 (-146.5) × 3.5-4.5-6µm, narrowly cylindrical or flexuous with obtuse, mucronate, moniliform or sometimes forked apices, thin-walled, filled with refractive contents, unchanging in SV.

Cheilocystidia

Resembling pleurocystidia.

Marginal cells

Not differentiated.

Pileipellis

A cutis, 70-110 µm thick, strongly gelatinized, orthochromatic in cresyl blue; hyphae 2-6 µm wide, narrowly cylindrical, septate, often with brown pigments; terminal cells (22-) 26-35.5-58 (-63) × 3-5-6 (-7) µm, cylindrical to narrowly clavate with obtuse or slightly acute apices, sometimes with brown pigments.

Pileocystidia

(53.5-) 55-62.5-76 (-90.5) × 3-4.5-7.5 µm, cylindrical to fusiform with obtuse, mucronate or forked apices, some filled with refractive contents, negative in SV.

Stipitipellis

A cutis; hyphae 1.5-4 µm wide, narrowly cylindrical, septate, many with brown pigments; terminal cells cylindrical or lageniform with obtuse apices.

Caulocystidia

Cylindrical to narrowly clavate with obtuse or slightly acute apices, up to 7 µm wide, thin-walled, filled with refractive contents.

Clamp connections

Absent.

NOTES

Both our phylogenetic analyses place our species firmly in sect. Polyphyllae Buyck & V.Hofst., being closely related to the North American R. eccentrica and already separated by a much longer branch from the Indian R. khanchanjungae Van de Putte, K. Das & Buyck ( Fig. 2 ). BLAST results of its ITS sequence in GenBank show top scores that are all <94% similar to our species, in this case for specimens collected in Japan and Korea ( Park et al. 2014). Russula ochrobrunnea S.Y.Zhou, Y.Song & L.H.Qiu , sp. nov., resembles R. eccentrica in overall morphology, but the latter has pink lamellae and much larger basidiospores (6-7.8 × 5-6 µm) and basidia (52-69 × 6.5-9.5 µm) ( Adamčík et al. 2018). Russula cartaginis Buyck & Halling , described from Costa Rica ( Buyck & Halling 2004) differs from R. eccentrica and our species in the presence of a brownish gill edge resulting from the presence of colored, branching marginal cells. Typical for most Polyphyllae is the often distinctly inflated lower portion of hymenial cystidia.

The Indian species R. khanchanjungae differs particularly by its crowded and forked lamellae becoming brown when bruised, and by the viscid and brown stipe with surface finely cracking exactly as the pileus surface; it also has much larger basidiospores (7.3-9.4 × 6.3-7.8 µm) and basidia (49-61 × 8-12 µm), as well as wider pleurocystidia (8-10 µm in width) ( Das et al. 2010). Also R. purpureonigra differs principally in its larger spores and crowded lamellae ( Manimohan & Latha 2011).

Figures

FIG. 7. — Russula ochrobrunnea S.Y.Zhou, Y.Song & L.H.Qiu, sp. nov. (GDGM 79718, holotype): A-D, fruiting bodies; E, F, scanning electronic micrographs of basidiospores. Scale bars: A-D, 1 cm; E, F, 1 μm.

FIG. 8. — Russula ochrobrunnea S.Y.Zhou, Y.Song & L.H.Qiu, sp. nov. (GDGM 79718,holotype):A, basidia;B, pleurocystidia;C, cheilocystidia; D, caulocystidia; E, terminal elements of pileipellis. Scale bars: A-D, 10 μm.

FIG. 2. — Maximum Likelihood tree of Russula Pers. subg.Archaeae Buyck & V.Hofst.and Compactae (Fr.) Bon based on LSU-mtSSU-tef1-rpb2-rpb1 combined sequences, bootstrap values higher than 70% were displayed around nodes. Scale bar: 0.02 substitutions.