Moniliophthora vaginicola T. Bau & W. N. Hou 2026, sp. nov.

Moniliophthora vaginicola T. Bau & W. N. Hou sp. nov. Figs 14 J – N, 17 Diagnosis. It is characterized by its cream pileus with a warm-brown center, flocculose-scaly stipe, and growth on withered Poaceae leaf sheaths. Etymology. “ vaginicola ” refers to its growth on withered, yellowing leaf sheaths near the base of living Poaceae plants. Description. Basidiomata small to medium-sized. Pileus 0.5–1.2 cm diam., initially convex, becoming nearly plane, centrally depressed; surface creamy white to cream-colored (RAL 9001), roughened; center warm brown (RAL 8003); margin with deep, longitudinal, radial grooves. Context thin, beige (RAL 1001). Lamellae adnate, relatively sparse, L = 13–16, I = 1, beige (RAL 1001) with a pinkish tint. Stipe 1.4–1.8 cm long, 1–2 mm thick, cylindrical, slightly thicker at apex, hollow; apex beige (RAL 1001) with a pinkish tint, middle clay brown (RAL 8001), base warm brown (RAL 8003); surface densely covered with cream-colored (RAL 9001), flocculent, fine scales. Basidiospores (8.4) 8.7–11 (12) × (5.1) 5.5–6.4 (6.7) µm, Q = (1.47) 1.48–1.93 (2.04) [1.66 ± 0.14], subellipsoid, thin-walled, hyaline, inamyloid. Basidia 35–41 × 8–10 µm, clavate, thin-walled, hyaline, inamyloid, 4 - (rarely 2 -) sterigmate; sterigmata 2.4–6.2 µm long. Basidioles 26–38 × 7–10 µm, clavate to cylindrical, smooth, thin-walled, hyaline, inamyloid. Cheilocystidia 16–29 × 5.8–11 µm, cylindrical, clavate to irregular, smooth, thin-walled, hyaline; apex bearing 1–3 digitate projections, projections 1.7–12 µm high. Pleurocystidia not observed. Lamellar trama irregular; hyphae 5–7 µm wide, thin-walled, hyaline, inamyloid. Pileus hairs 80–258 × 5.1–7.9 µm, setose, inamyloid, densely arranged, thick-walled to solid, apex slightly acute, sometimes bearing a single digitate projection. Pileus trama a cutis; hyphae 4–6.3 µm wide, slightly thick-walled, smooth, inamyloid, pale brown in water, unchanged in 5 % KOH. Stipe hairs 58–145 × 4.5–7.1 µm, setose, thick-walled to solid, apex acute. Stipe trama composed of parallel, thick-walled, smooth hyphae 3.4–5.4 µm wide. Clamp connections present in all tissues. Typus. CHINA • Inner Mongolia Autonomous Region, Tongliao City, Horqin Left Back Banner, Wudantala Forest Farm, on yellowing leaf sheaths, Poaceae plants, 43°00'59"N, 122°44'36"E, alt. 217 m, 15 July 2023, T. Bau & W. N. Hou, FJAU 69463 (H 230758), holotype!. Additional materials examined. CHINA • Inner Mongolia Autonomous Region, Tongliao City, Hure Banner, on withered leaf sheaths, Cyperaceae plants, 42°45'47"N, 121°46'17"E, alt. 352 m, 17 July 2023, T. Bau & W. N. Hou, FJAU 69464 (H 2307166). • Inner Mongolia Autonomous Region, Tongliao City, Horqin Left Middle Banner, Wusitu Nature Reserve, on yellowing leaf sheaths, Poaceae plants, 43°47'47"N, 123°17'43"E, 148 m asl, 21 July 2023, T. Bau & W. N. Hou, FJAU 69465 (H 2307246). MONGOLIA • Dornod Province, Matad, on yellowing leaf sheaths, Poaceae plants. 47°40'09"N, 116°54'27"E, alt. 626 m, 23 December 2024, T. Bau & B. Ganbaatar, FJAU 69435 (B 23005). • Dornod Province, Matad, on withered, yellowing leaf sheaths near the base of living Poaceae plants, 47°40'09"N, 116°54'27"E, alt. 626 m, 23 December 2024, T. Bau & B. Ganbaatar, FJAU 69434 (B 23020). Notes. Phylogenetic analyses show that the GenBank sequence PQ 732594, labeled as P. palmivorus (Sharples) Antonín & M. Kolařík and derived from specimen UBA 23005, forms a well-supported independent clade with the examined specimens (PP = 1, UFBoot = 100 %). Examination of specimen UBA 23005, collected from Mongolia by Burenbaatar Ganbaatar, reveals that its morphological characters are consistent with those of the examined materials. Based on both phylogenetic evidence and morphological comparison, these specimens are therefore regarded as conspecific. Furthermore, the presence of a pileipellis with dense setae, together with its placement within the Moniliophthora clade (PP = 1, UFBoot = 99 %), indicates that this taxon is better assigned to Moniliophthora rather than Paramarasmius. Basidiomatal pileus color is variable and often relatively vivid among the 15 currently recognized species of Moniliophthora. To be specific, Mo. pakistanica Izhar, Asif, Niazi & Khalid and Mo. ticoi (Halling) Niveiro, N. A. Ramírez, Lodge & Aime exhibit orange tones, Mo. mayarum Lodge, Aime & Niveiro displays reddish tones, and Mo. purpurea Fatima & Khalid presents purplish tones (Izhar et al. 2022; Haqnawaz et al. 2024; Niveiro et al. 2020). The nearly cream-colored pileus surface of this species clearly differs from those of other known species in the genus. As indicated by the above findings, basidiomatal pigmentation may provide useful auxiliary evidence for species delimitation, although it should not be considered a shared diagnostic character of Moniliophthora. The phylogenetic analyses involved sequence data from as many Moniliophthora species as possible. The resulting tree indicates that the recently described Mo. sclerotium is closely related to this species. Nevertheless, Mo. sclerotium is most readily distinguished by the production of subglobose, ellipsoid to irregular sclerotia, whereas sclerotia are absent in Mo. vaginicola (Zhang et al. 2025). At present, Mo. sclerotium usually occurs from scattered to gregarious on decaying wood and is known only from Yunnan Province.