Russulales » Russulaceae » Russula

Russula pseudomodesta

Russula pseudomodesta Paloi, Suwannarach N. & Kumla

MycoBank number: MB 848802, Index Fungorum: IF848802

Basidiomata large- to medium-sized. Pileus 60−125 mm diam., convex or ovoid at early stage, become broadly convex to plano-convex with slightly depressed center; surface smooth to pruinose, greenish gray (1A2), yellowish gray (2B2−3B2), grayish yellow (3C3), orange gray (5B2−6B2), grayish orange (5B3−6B3), grayish green (25B2) to sometimes reddish gray (7B2) at center, becoming fed toward margin grayish white (1A2), yellowish white (2A2), gray (3B1) to sometime white (1A1), no change after bruising, turned orange with 10% KOH, light pinkish withguaiacol; margin wavy, cracked at maturity, striate; context up to 5 mm at the middle, white to off-white, no change after exposed to air. Lamellae adnate, up to 8 mm wide, regular, sometimes bi-forked near stipe, white (1A1), no change after bruising; edge smooth, concolorous; lamellulae zero to one in a row. Stipe 35−52 × 11−18 mm, central, more or less equal, cylindrical, sometimes slightly bulbous base; surface smooth to pruinose, white (1A1), no change after bruising, turned yellow with 10% KOH, light pinkish with guaiacol; context firm, white (1A1), becoming light yellowish after exposed to air. Odor not recognized, not hard. Taste mild. Spores print white to off white.

 

Basidiospores 5.5−6.4−7.2 × 5.1−5.6−6.5 μm, Q = 1.0−1.1−1.1, globose to sub-globose, ornamentation amyloid, composed with 0.3−0.5 μm low to 0.7−1.1 μm high warts, few connected (1−3) together with fine line, 0.1 μm high, among warts with very small warts present, never reticulate, suprahilar spot, inamyloid. Basidia 35.5−53.5 × 9−11.5 μm, clavate to sub-clavate, sometimes cylindrical, thin-walled, hyaline, oil granules present when viewed with 5% KOH, 4-spored; sterigmata 3−5.5 μm long, cylindrical. Lamellae edge composed of cystidia and basidia. Subhymenium pseudoparenchymatous. Hymenial cystidia 66−87 × 10−13 μm, cylindrical to sub-cylindrical or fusiform with short appendiculate to moniliform or sometimes obtuse apex, thin-walled, hyaline, heteromorphous contents present near gill edge; same as gill side. Pileipellis orthochromatic in cresyl blue, context composed with sphaerocytes; subpellis composed with densely arranged hyphae, 125−150 μm deep, gelatinized, hyphae 2.5−4 μm broad, thin-walled, hyaline, branched; suprapellis 95−150 μm deep, less gelatinized, composed with erect to sub-erect hyphal end, 30−65 × 2.5−7 μm, thin-walled, sometimes thick walled, septet, hyaline, hyphal end obtuse to sometimes pointed, subterminal cells 5.5−16.5 × 5−10.5 μm, globose, sub-globose to ellipsoid, thin-walled, hyaline, 3−5 cells in a row. Pileocystidia rare at margin, comparatively frequent toward center, different types, clavate to sub-clavate or sub cylindrical with obtuse to less pointed or moniliform to mucronate, 25−50 × 5−6.5 μm, sometimes very long 75−90 × 5.5−7.5 μm, cylindrical with obtuse to mucronate apex, one celled, thin-walled, hyaline, oil granule present with 5% KOH. Stipitipellis composed with tightly arranged, interwoven hyphae, 3−4.5 μm broad, thin-walled, hyaline, branched, septate, hyphal end obtuse to clavate; context composed with sphaerocytes. Caulocystidia abundant, different shaped, 17−54 × 3.5−6 μm, few are very long, 4−6 μm wide, clavate to sub-clavate or sub-cylindrical with obtuse to round apex to moniliform or mucronate thinwalled, hyaline, oil granules present with 5% KOH. Clamp connection absent in all tissue.

 

Ecology and distribution: Solitary to caespitose, growing under trees of Shorea spp. (Dipterocarpaceae). Known only from the type locality in Northern Thailand.

 

Additional material examined: Thailand, Chiang Mai Province, Chiang Mai University premises, 18°480.8496N;98°5721.2256E, elevation 335 m, 28 August 2022, S. Paloi and W. Phonrob, (SDBR-CMUSOU33). GenBank accession numbers OQ957482 (nrITS) and OQ968301 (nrLSU).

 

Fig. 1 A combined (nrITS+nrLSU) phylogram derived from maximum likelihood analysis of 62 taxa. Three Russula species, R. nigricans, R. dissimulans, and R. camarophylla were used for rooting purposes. The numbers above branches represent maximum likelihood bootstrap percentages (right) and Bayesian posterior probabilities (left). Bootstrap values ≥ 75% and Bayesian posterior probabilities ≥ 0.90 are shown above the branches. The scale bar represents the expected number of nucleotide substitutions per site. Type sequences highlighted in bold front. Newly reported species in this study are highlighted (blue front) and corresponding species pictures are provided.