Inocybe subchondrospora A. H. Zhu, Hai X. Ma & Y. P. Ge, 2025

Zhu, An-Hong, Xu, Yan-Ru, Ma, Hai-Xia & Yu, Wen-Jie, 2025, Three nodulose-spored Inocybe (Agaricales, Basidiomycota) species discovered from Motuo, Southwest China, MycoKeys 122, pp. 99-121 : 99-121

Inocybe subchondrospora A. H. Zhu, Hai X. Ma & Y. P. Ge sp. nov.

Figs 6 , 7

Etymology.

Refers to the basidiospore morphology which is similar to I. chondrospora .

Holotype.

China • Xizang Autonomous Region: Motuo County, Bangxin Town, along Motuo Highway , in sandy soil under conifer-broadleaf mixed forest, alt. 2,429 m, 13 June 2024, leg. Hai X. Ma & A. H. Zhu, FCATAS 12445 (XZ 1230). GenBank accession numbers: ITS ( PV 827765 ); LSU ( PV 833642 ); RPB 2 ( PV 845800 ).

Diagnosis.

Basidiomata small, Pileus brown to reddish brown; lamellae subcrowded; stipe cylindrical with a swollen base, brown to reddish brown, entirely pruinose. Basidiospores oblong-ellipsoid to phaseoliform, regular; hymenial cystidia broadly fusiform with a tapered base and usually forming a short pedicel, walls thickened, yellow, Caulocystidia descending to stipe base. Occurs in broad-leaved forests in tropical Xizang, China. Most similar to I. chondrospora , but differs from it by an appressed-fibrillose to nearly glabrous pileus, smaller basidiospores, broader hymenial cystidia, and an ecology in subtropical evergreen forests.

Description.

Basidiomata small-sized. Pileus 15–20 mm diam., initially hemispherical to subglobose, becoming convex to plano-convex with age, developing a low obtuse umbo at maturity; margin persistently incurved in young specimens, decurved in age; surface dry, matte, radially striate near margin; disc umber (7 B 6) to chestnut brown (6 E 4), gradually fading to yellowish brown (5 A 5–6 A 6) towards margin. Lamellae adnexed, close, with 3–4 tiers of lamellulae; lamellar face brownish yellow (5 D 6) when dry, developing sparse dark brown (5 E 4) maculations; edges fimbriate, concolorous with faces. Stipe 15–19 × 2–3 mm, eccentric, terete, solid; surface densely white-pruinose (1 A 1) at apex, becoming fibrillose-striate downwards; apex strong brown (6 E 7) with punctate protrusions, gradually transitioning to brown (6 B 6) at base. Context fleshy in pileus, 2–3 mm thick at dis, fibrillose in stipe; yellowish white overall, developing brownish tones near stipe base. Odor not distinctive.

Basidiospores [100 / 2 / 2] ( holotype) mostly ellipsoid to oblong-ellipsoid, (9.5) 10.1–11.4 – 12.9 (13.4) × (5.9) 6.0–6.6 – 7.2 (8.1) μm, Q = (1.3) 1.5–1.7 – 1.9 (2.0), Q m ± SD = 1.73 ± 0.134; less often phaseoliform, 9.5–10.9 – 11.9 × 5.9–6.5 – 8.1 μm; smooth, yellow-greenish in KOH, containing 1–2 yellowish refractive oil droplets. Basidia 14–18 – 22 × 6–7 – 9 μm (n = 30), predominantly clavate to cylindrical, 4 - sterigmate (occasionally 2 - sterigmate); sterigmata 2–8 μm long; contents yellowish with granular inclusions. Pleurocystidia 41–49 – 59 × 17–21 – 27 μm (n = 30), fusoid-ventricose with broad basal pedicels (3–5 μm wide), walls thickened apically (2–4 μm), yellow-green in KOH. Cheilocystidia 40–46 – 60 × 11–22 – 25 μm (n = 30), morphologically similar to pleurocystidia. Cheiloparacystidia 9–14 – 20 × 8–11 – 15 μm (n = 30), clavate, thin-walled, hyaline. Hymenophoral trama regular, 38–72 μm wide; hyphae cylindrical to inflated (7–30 μm diam.), thin-walled, yellowish. Pileipellis 48–130 μm thick, cutis-type; hyphae parallel, 7–24 μm diam., walls yellowish brown with encrusted pigments. Stipe trama composed of parallel, cylindrical hyphae 6–14 μm diam. Caulocystidia 38–42 – 47 × 14–17 – 20 μm (n = 30), fusoid, thick-walled (2–3 μm), concentrated at stipe apex. Oleiferous hyphae present in all tissues, 3–12 μm diam., bright yellow, irregularly contorted. Clamp connections abundant throughout all tissues.

Habitat and distribution.

Gregarious in sandy soils of subalpine zone ( 2,400 –2,500 m elev.); currently known only from the type locality in southeastern Xizang, also found in subtropical evergreen broad-leaved forests in Hubei province.

Additional specimens examined.

China • Xizang Autonomous Region: Motuo County, Bangxin Town, along Motuo Highway , in sandy soil under conifer-broadleaf mixed forest, alt. 2,429 m, 13 June 2024, leg. Hai X. Ma & A. H. Zhu, FCATAS 14836 (XZ 1230 A); GenBank accession numbers: ITS ( PV 834866 ); LSU ( PV 834864 ); RPB 2 ( PV 847674 ) • Hubei Province: Yichang City , Wufeng Tujia Autonomous County, 17 June 2024, in subtropical evergreen forests dominated by fagaceous trees, Y. P. Ge, Q. Na, J. W. Guo, G. Y. Qiu & L. J. Wang, NJ 5283 ( FCAS 4254 ). GenBank accession numbers: ITS ( PV 834856 ); LSU ( PV 834860 ) .

Remarks.

Inocybe subchondrospora is distinguished by small, reddish-brown to cinnamon-brown basidiomata, a convex to plano-convex pileus, and pruinose stipes with a swollen but non-marginate base. Microscopically, it exhibits ellipsoid to elongate basidiospores with obtuse apices and broadly fusiform hymenial cystidia bearing small pedicels. Phylogenetically, I. subchondrospora forms a sister lineage to the north temperate taxon I. chondrospora (syn. I. immigrans Malloch ), with this clade itself sister to I. kuberae Bandini & B. Oertel.

Inocybe chondrospora resembles the new species in basidiomata coloration and spore shape but differs in having a tomentose-scaly pileus, significantly larger basidiospores, larger hymenial cystidia (pleurocystidia: 38–80 × 11–28 µm), and an ecological preference for sandy soils associated with Betulaceae , Orchidaceae , Pinaceae , and Salicaceae ( Dovana et al. 2023) . In contrast, I. kuberae shares the dark brown pileus and pruinose stipe but diverges in nodulose spores (avg. 11.8 × 8.9 µm), ventricose (sub) lageniform hymenial cystidia, and occurrence on calcareous soils at subalpine elevations ( Bandini et al. 2022).

Figures

Figure 6. Basidiomata of Inocybe subchondrospora. a, b. XZ 1230 (holotype); c – e. NJ 5283. Photos by Hai X. Ma and Y. P. Ge. Scale bars: 10 mm (a – e).

Figure 7. Microscopic features of Inocybe subchondrospora (XZ 1230, holotype). a, b. Basidiospores; c. Basidia; d – g. Cheilocystidia and cheiloparacystidia; h. Pleurocystidia i. Cross-section of lamellae; j. Hymenophoral trama hyphae; k. Caulocystidia on stipileipellis hyphae; l. Stipileipellis hyphae; m. Stipe trama hyphae; n. Pileipellis; o. Pleipellis hyphae; p. Stipe trama hyphae; q. Oily hyphae. Photos by Y. R. Xu. Scale bars: 10 μm (a – c, j, l – m, o – q); 20 μm (d – h); 50 μm (i, k, n).