Russula pseudoamoenicolor A. Ghosh, Buyck, K. Das, A. Baghela & R.P. Bhatt

MycoBank: MB 817101 Facesoffungi number: FoF02522

Etymology: referring to the lookalike of Russula amoenicolor, an European species.

Holotype: CAL 1330.

Basidiomata up to 100 mm in height. Pileus 50–100 mm in diam., globose, plano-convex to applanate with broadly depressed center, becoming uplifted when mature; margin decurved, entire, tuberculately striate, torn when mature, surface dry, viscid when moist, subvelvety, purplish-red-violet-red (14B5–14B8) or light lilac, light violet to pastel violet (16A4–16A5) with purplish-white (14A2) to violet-white (16A2) towards margin, rarely dark violet (15A6–15A8) towards the depression; cuticle peeling 3/4th of the radius; cap context white (1A1–2A1), unchanging when bruised. Lamellae adnexed to subdecurrent, close to rather crowded, white (1A1–2A1), forked near the stipe; edges marginate near the cap margin, lamellulae absent. Stipe 45–70 × 10–14 mm, equal, slightly tapered towards the base, dry, smooth, brittle, central, reddish-white to pink-rose or pink-red (12A3–12A5), context stuffed, white (1A1–2A1), pinkrose (12A3–12A5) with guaiacol. Taste mild. Spore print not obtained. Basidiospores 6–7.30–9.5 × 5–6.33–8 um (n= 25, Q = 1.03–1.16–1.33), subglobose to broadly ellipsoid, rarely ellipsoid, ornamentation amyloid, composed mostly of ridges and warts (up to 1 um high) aligned or connected to form an incomplete reticulum, with few isolated warts, apiculi up to 2 um high. Basidia 35–55 × 9–13 um, cylindrical, subclavate to clavate, 4-spored, sterigmata up to 6 um high. Subhymenium layer up to 30 um thick, pseudoparenchymatous. Hymenophoral trama mainly consisting of sphaerocytes measuring 17–40 × 16–34 um. Pleurocystidia 90–117 × 10–21 um, ventricose, subfusiform to fusiform with blunt apex, thick walled (1 um thick), emergent up to 60 um; content blank or insignificant. Gill edges fertile, with basidia and cystidia. Cheilocystidia 30–85 × 7–10 um, same as pleurocystidia. Pileipellis up to 90 um thick, composed of clustered erect to suberect elements composed of chains of 4–7 cells; terminal cells ellipsoid, conical, subfusoid to occasionally subulate (11–65 × 4–10 um wide); subterminal cells mostly cylindrical to rectangular, few ellipsoid or rounded (inflated), measuring up to 14 um wide.

Habitat and distribution: grows in close association with Quercus sp. with undergrowth of Rhododendron sp. in moist deciduous and mixed (broadleaf and coniferous) forest.

Material examined: INDIA, Uttarakhand, Pauri Garhwal, along the road side of khirsu, alt. 1835 m., N3010.1550 E7852.1340, 24 July 2015, A. Ghosh, AG 15-739 (CAL 1330, holotype)

Notes: The combination of characters in Russula pseudoamoenicolor comprising a purplish-red to violet-red or lilac subvelvety pileus with darker center, reddish-violet to pink-rose stipe, occasional occurrence of typically subulate terminal cells of pileipellis, absence of dermatocystidia and inamyloid suprahilar spot place it in R. subg. Amoenula Sarnari. In the field, the European species, R. amoenicolor Romagn. appears to be quite similar to the present taxon but the former (Sarnari 1998) has purple to green or variegated pileus, smaller basidiospores (6.7–8.4 x 5.6–7.4 um) and mostly subulate terminal cells in pileipellis (terminal cells mainly ellipsoid, conical, subfusoid or occasionally subulate in R. pseudoamoenicolor) and its ITS nucleotide sequence are dissimilar (93 % identity with R. pseudoamoenicolor for 100 % query coverage using BLAST) from the present species. From a phylogenetic standpoint, R. pseudoamoenicolor is closely related to R. violeipes and cluster together in a subclade with high bootstrap support. The European species, R. violeipes Que´l. was recently reported from South Korea (Park et al. 2013), yet these collections differs significantly from European material (GenBank acc. no. AY061726). These Korean collections (GenBank accession nos. KF361797 and KF361783) are here, however, recovered as identical to our material from the Indian Himalaya. Interestingly, two Australian species, R. variispora T. Lebel and R. rostraticystidia T. Lebel, previously of undetermined position within R. subg. Heterophyllidia (Lebel and Tonkin 2007) are here for the first time recovered with significant support (93 % BS) as very closely related to or likely members of R. subsect. Amoeninae. Russula variispora and R. rostraticystidia both are sequestrate species and hence, have an altogether different morphology from other known Amoeninae, or even from all other known species in R. subg. Heterophyllidia as secotioid-gasteroid taxa have never been reported from other subsections in this subgenus (Kong et al. 2015). The rostrate pleurocystidia of R. rostraticystidia and the similarly shaped terminal cells in the less developed pileipellis of these Australian secotioid species (Lebel and Tonkin 2007) support their placement in Amoeninae.

Russula pseudoamoenicolor (holotype). a, b Fresh basidiomata. c–e Transverse section through lamellae showing pleuromacrocystidia. f Radial section through pileipellis. g–j Elements of pileipellis. k Basidiospores. l SEM micrograph of basidiospores. Scale bars a = 100 mm; c, d = 50 um; e, g–k = 10 um; f = 100 um; l = 2 um

Russula pseudoamoenicolor (holotype). a Fresh and/or dissected basidiomata. b Radial section through pileipellis. c Basidiospores. d Pleurocystidia. e Basidia. f Cheilocystidia. Scale bars a = 10 mm; b–f = 10 um

Phylogram generated from maximum likelihood method based on ITS-rDNA sequences: The evolutionary history was inferred by using the maximum Likelihood method based on the Kimura 2-parameter model (Kimura 1980). The tree with the highest log likelihood (-2215.6038) is shown. One-thousand bootstrap replicates were analyzed to obtain the nodal support values. The novel species having GenBank Accession Number KX234819 (ITS-r-DNA) is shown in blue. The R. emetica and R. nana were considered as the out group taxa. Evolutionary analyses were conducted in MEGA6 (Tamura et al. 2013)