Lactarius parvihatsudake X.H. Wang, J.B. Pu & Xia Chen, 2024

Pu, Jin-Bao, Cao, Shu-Qin, Wang, Ran, Chen, Xia, Pang, Chun-Mei & Wang, Xiang-Hua, 2024, New species diversity and host association of Lactarius sect. Deliciosi: describing L. gibbosus and L. parvihatsudake (Russulaceae, Russulales) in southern China, Phytotaxa 668 (3), pp. 226-238 : 233

Lactarius parvihatsudake X.H. Wang, J.B. Pu & Xia Chen , sp. nov., Fig. 4

MycoBank number: MB 854362

Etymology:—referring to the resemblance to L. hatsudake but with smaller basidiocarps.

Holotype:— CHINA: Zhejiang Prov., Hangzhou, Lin’an District, Tianmu Mt. National Nature Reserve, Laodian, N30º20′30.04′′ E119º25′59.42′′, elev. 1105 m, in mixed forest with trees of Pseudolarix amabilis, Cryptomeria japonica var. sinensis, Chamaecyparis pisifera, Cunninghamia lanceolata and Indocalamus tessellatus , 17 Sept. 2021, coll. J.B. Pu, no. FC330112210295 (KUN-HKAS 135138! GenBank: ITS PP887460; gpd PP898314; nuc-LSU PQ273276; rpb1 PQ274844; rpb2 PQ274832; tef1 PQ274838).

Diagnosis:—Differing from L. hatsudake in the smaller and thin-fleshed basidiocarps, distant lamellae and azonate pileus. It grows in Pseudolarix amabilis forest whereas L. hatsudake in pine forest.

Basidiocarps small to medium-sized, fleshy. Pileus 20–50 mm in diam., involute when young, soon plano-applanate with depressed center, infundibuliform when fully mature; surface smooth, greasy, strongly hygrophanous, azonate, red to grayish red when wet, fading to pale ochraceus with greenish tinge at dry places, centre often dry and fading, grayish or dull red at the margin, margin or even the whole pileus often transparently radially striate; context 1–2 mm thick, pale grayish red, unchanging. Lamellae 2–4 mm broad, distant to subdistant, short decurrent, grayish red, with more or less purplish tinge when fully mature, duller when bruised, not changing to green or blue. Stipe 20–40 × 3–5 (7) mm, central, cylindrical, equal or slightly tapering upwards, hollow; surface concolorous with or duller than lamellae, some changing to yellowish brown when old. Latex scanty, dull vinaceous red, unchanging. Spore print unknown.

Basidiospores (120/6/5) (7.5) 8.0– 8.7 –9.5 (10.0) × 6.5– 7.3 –8.0 (8.5) μm [holotype: (40/2/1) 7.5– 8.6 –9.5 × 6.5– 7.3 –8.0 (8.5) μm], broadly ellipsoid to ellipsoid [Q = (1.09) 1.11–1.29 (1.31), Q = 1.19 ± 0.05] [holotype: Q = (1.12) 1.13–1.27 (1.29), Q = 1.19 ± 0.05]; ornamentation 0.5–1.5 (1.8) μm high, composed of medium acute ridges partially connected, not forming a reticulum, closed meshes rare, sometimes with transparent dots, free ridges and isolated warts present but uncommon; plage not amyloid. Basidia 45–70 × 10–15 µm, clavate, 4-spored. Pleuromacrocystidia very rare, absent in some individuals, 25–50 × 5–7 μm, embedded in hymenium, not projecting beyond the basidia, base originating from hymenium or even higher than the basal septa of basidia, subfusiform to clavate with a tapering apex, with colorless, pale yellowish brown or golden-brown contents. Hymenial pseudocystidia common to abundant, 2–5 μm broad, with pale golden-brown to golden-brown contents, filiform, tortuous, sometimes forking at apex. Lamella edge sterile; cheilomacrocystidia rare, absent in some individuals, similar to pleuromacrocystidia in shape but smaller; marginal cells 10–20 (30) × 4–6 (8) μm, cylindrical, clavate, some bending, hyaline. Pileipellis an ixocutis to ixolattice, 100–200 μm thick, sometimes covered with a hyphae-free gluten layer (up to 30 μm), of loosely interwoven hyphae; hyphae 2–7 μm broad, nearly colorless, some shrivelled, slightly to strongly gelatinized, terminal hyphae 20–50 × 3–4 μm. Lactiferous hyphae abundant, 3–9 μm broad, golden brown. Stipitipellis an ixocutis, 30–50 μm thick, of hyphae compactly interwoven; hyphae 2–5 μm broad, colorless, not gelatinized. Trama of pileus and stipe with abundant rosettes. Clamp connections absent.

Additional specimens examined:— CHINA: Zhejiang Prov.,Hangzhou,Lin’an District,Tianmu Mt.National Nature Reserve, Fuyushanzhuang, N30º18′41.57′′ E119º26′39.61′′, elev. 323m, 06Jun.2021, coll.J.B. Pu, no.FC330112210125 (KUN-HKAS 135137; GenBank: ITS PP887459; gpd PP898313; nuc-LSU PQ273277; rpb1 PQ274845; rpb2 PQ274833; tef1 PQ274839); Tianmu Mt. National Nature Reserve, Laodian, N30º20′35.36′′ E119º26′16.18′′, elev. 1156 m, in mixed forest with Pseudolarix amabilis, Cryptomeria japonica var. sinensis, Chamaecyparis pisifera, Cunninghamia lanceolata and Indocalamus tessellatus , 17 Sept. 2021, coll. J.B. Pu, no. FC330112210304 (KUN-HKAS 135139; GenBank: ITS PP887458; gpd PP898312; nuc-LSU PQ273278; rpb1 PQ274846; rpb2 PQ274834; tef1 PQ274840); Hangzhou Botanical Garden, in introduced plantation of P. amabilis , 07 May 2024, coll. Y.J. Lu, s.n. (KUN-HKAS 135136; GenBank: ITS PP887463; gpd PP898317); ibid., 11 May 2024, coll. Y.J. Lu, s.n. (KUN-HKAS 135135; GenBank: ITS PP887462; gpd PP898316; nuc-LSU PQ273279; rpb1 PQ274847; rpb2 PQ274835; tef1 PQ274841). Jiangsu Prov., Nanjing Botanical Garden Mem. Yun Yat-Sen, in introduced plantation of P. amabilis , N32º3′31.25′′ E118º49′58.04′′, elev. 61 m, 04 Oct. 2023, coll. X. Chen, no. CX795 (KUN-HKAS 135133; GenBank: ITS PP887461; gpd PP898315; nuc-LSU PQ273280; rpb1 PQ274848; rpb2 PQ274836; tef1 PQ274842).

Note: In the field, L. parvihatsudake is reminiscent of L. hatsuadake , but the smaller basidiocarps, distant lamellae and transparently sulcate pileus margin make it different. This is a thin-fleshed species and the pileus is never zonate as L. hatsudake . The spores are bigger and broader, the ornamentation of the spores is higher and the macrocystidia are smaller. Another notable difference from other red-colored species is the habitat with Pseudolarix amabilis , a relict genus/species that has never been reported to be host of the species in the section. The closest relative of L. parvihatsudake is not clear, but apparently not related with L. hatsudake and another Asian red-colored species L. horakii . In both ITS and gpd phylogenies, this species formed a long branch, suggesting an early divergence. This genetic divergence might be from the host specificity with the relict host Pseudolarix amabilis , similar to L. guangdongensis ( Han et al. 2019) , if the symbiotic relationship is eventually confirmed.

Figures

FIGURE 4. Lactarius parvihatsudake. A–C: basidiocarps, D: basidiospores, E: pleuromacrocystidia, F: pseudocystidia, G: lamella edge, H: pileipellis. (scale bars: A-C: 1 cm, D: 5 µm, E and F: 20 µm, G and H: 25 µm).A, D–F and H from holotype (KUN-HKAS 135138), B and G from KUN-HKAS 135133, C from KUN-HKAS 135136.