Russula botrytigustata Tondeleir & Verbeken 2026, sp. nov.

Russula botrytigustata Tondeleir & Verbeken sp. nov. Figs 3, 5 Diagnosis. Sequestrate with strongly reduced columella, pileus yellowish white; spores with an almost complete reticulum; hymenial cystidia lageniform, mucronate; pileocystidia cylindrical to subclavate, long and slender. Holotype. Sri Lanka • A. Verbeken 07-177 (GENT); near Sinharaja Forest; 16 Dec. 2007. Etymology. botrytigustata (Lat. adj.): from botrytis, the varietal epithet of Brassica oleracea var. botrytis (cauliflower), and gustata (“ tasted ”), referring to the distinctive cauliflower-like taste of the basidiomata. Description. Basidiomata sequestrate, epigeous, subglobose, somewhat flattened, 15 mm in diameter. Columella strongly reduced, greyish hyaline. Pileipellis yellowish white (4 A 2), smooth, with gelatinous veins in transparency. Hymenophore greyish yellow (4 B 3-4), with labyrinthoid loculi that are longer towards the stipe. Context without odor; taste distinctly like raw cauliflower; chemical reactions not observed. Spore print not observed. Basidiospores 5.6–7.4 – 9.2 (– 9.4) × 5.0–6.3 – 7.5 (– 7.8) µm, some spores substantially larger, likely originating from 2 - spored basidia, then 10.5–12.2 µm, broadly ellipsoid, Q = (1.05 –) 1.11–1.18 – 1.25 (– 1.28); thick-walled; ornamentation of moderately distant, 0.2–0.4 µm high amyloid warts [4–5 in a 3 µm diam. circle], (sub) reticulated and without isolated elements, fused by long ridges [4–5 (– 8) in a 3 µm diam. circle]; suprahilar spot amyloid with similar but lower ornamentation; suprahilar appendix 0.5 to 1.5 µm long, without sterigmatal appendix. Basidia clavate, 2 -, 3 -, or 4 - spored, (24.2 –) 25.8–31.3 – 36.8 (– 43.5) × (6.6 –) 7.9–9.3 – 10.6 (– 12.0) µm; sterigmata 4–7 µm long and curved or rarely straight, thin-walled, hyaline. Basidioles narrowly clavate to clavate, 7–9 µm wide, hyaline. Hymenial cystidia widely dispersed, 40–50 per mm 2, lageniform, mucronate, (33.3 –) 42.6–51.9 – 61.2 (– 67.7) × (7.8 –) 8.3–9.9 – 11.4 (– 13.8) µm, extending up to 20 µm from the hymenium, with a (5 –) 15–30 µm long, tortuous appendix that is rarely branched; contents heteromorphous, coarsely crystalline or hyaline, without reaction in sulfovanillin, turning yellowish in Melzer. Subhymenium consisting of 1–2 tiers of cells, parenchymatous to ramose, 9–13 × 13–19 µm. Hymenophoral trama consisting of sphaerocytes of diameter 12–24 µm, with few cystidioid hyphae. Pileipellis orthochromatic in Cresyl Blue, 140 µm thick, gradually passing into the underlying trama. Suprapellis 15–25 µm thick, ungelatinized, consisting of compact flexuous hyphae with ascending to erect hyphal terminations, gradually passing into thin subpellis, consisting of loose 3–4 µm thick hyphae and 4–5 µm thick cystidioid hyphae. Hyphal terminations near the pileus center dispersed and inconspicuous, narrow and thin-walled, occasionally branched, cylindrical, nodulose and flexuose, rarely apically obtuse, sometimes encrusted; terminal cells (21 –) 27.6–36.5 – 45.4 (– 49) × (2.5 –) 2.7–3.0 – 3.2 (– 3.5) µm. Subterminal cells more or less equal in size, rarely branched. Hyphal terminations near the pileus margin similar in shape but slightly shorter; (13.7 –) 26.3–34.1 – 42.0 (– 49) × (2.1 –) 2.6–3.0 – 3.5 (– 3.8) µm. Pileocystidia near the pileus center abundant, 1 - celled, (42.0 –) 54.6–106.5 – 158.4 (– 270.0) × (4.0 –) 4.9–6.1 – 7.3 (– 9.0) µm, cylindrical to subclavate, rarely obtuse, extending deep into the subpellis, thin-walled, with heteromorphous, finely to coarsely crystalline contents that are sometimes banded. No reaction in sulfovanillin. Pileocystidia near the pileus margin similar in size, abundance, and shape; 45.0–109.2 – 173.4 (– 298.0) × (4.5 –) 5.0–6.2 – 7.4 (– 8.0) µm. Cystidioid hyphae abundant in subpellis, scarce in hymenophoral trama. Oleiferous hyphae absent. Habitat. Primary rainforest with Shorea spp. Notes. Russula botrytigustata shares barely any morphological characteristics with representatives of the R. castanopsidis / R. tapawera lineages. Some representatives, such as R. tapawera (T. Lebel) T. Lebel, exhibit a similar configuration of the pileipellis, but this feature is highly variable within this lineage (McNabb 1973; Lebel 2002; Adamčík et al. 2019). Moreover, all species in the R. castanopsidis lineage exhibit isolated ornamentation with only a few line connections, in contrast to the (sub) reticulated ornamentation of R. botrytigustata. The presence of mucronate hymenial cystidia appears to be the only shared characteristic. For this reason, and given its phylogenetically distinct position, we assume that R. botrytigustata represents the first described species from a thus far unrecognized lineage. This species shows some similarities with the Australian sequestrate species R. parvisaxoides (T. Lebel) T. Lebel by sharing mucronate hymenial cystidia and lacking a prominent stipe or columella. However, the spores of this species are much larger (8.5–11 × 7–10 µm), with less reticulate ornamentation, and pileocystidia are absent. As no phylogenetic placement of this species has been provided in earlier studies, we performed a BLAST search of the ITS sequence of the type material, which suggests placement in R. subsect. Cyanoxanthinae Singer. No other sequestrate species from Australasia shows similar spore ornamentation.