Pseudochaetosphaeronema baoshanense L. Lu, K. D. Hyde & Tibpromma

Pseudochaetosphaeronema baoshanense L. Lu, K. D. Hyde & Tibpromma Fungal Diversity 25: 1–275 (2025) Fig. 2 Description. Saprobic on a decaying branch of Hevea brasiliensis. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata 140–170 × 170–200 μm (x ̄ = 153 × 184 μm, n = 10), solitary, globose to subglobose or pyriform, dark brown, immersed or erumpent, with black spots on the host surface, unilocular. Conidiomatal wall 50–60 μm wide, composed of two layers, outer layers brown, inner layers pale brown to hyaline, arranged in a textura angularis to textura prismatica, darker at the outer layer, fusing and indistinguishable from the host tissues. Conidiophores arising from the inner layers lining the conidioma, or at the base, often reduced to conidiogenous cells. Conidiogenous cells 6–10 × 2–3 μm (x ̄ = 7.23 × 2.14 μm, n = 15), monophialidic, cylindrical, integrated, hyaline or pale brown, smooth-walled. Conidia 11–15 × 5–6 μm (x ̄ = 12.4 × 5.6 μm, n = 40), oblong to ellipsoidal, or fusoid, with rounded ends, sometimes truncate and narrow at the base, yellowish to pale brown, smooth, thick-walled, 1–3 - septate, some slightly constricted at the septum. Culture characteristics. Conidia germinated on PDA within 12 hours. Colonies circular, raised, brown, with entire margin; reverse dark brown at the center, fading to pale brown at the edge. Material examined. China, • Yunnan Province, Dehong Dai and Jingpo Autonomous Prefecture, Mang City, on a decaying branch of Hevea brasiliensis, 18 April 2024, Rui-Fang Xu, DHR 23 (GMB-W 1227), living culture GMBCC 2337; China, Yunnan Province, Lincang City, 28 July 2022, LCR 24 (GMB-W 1228), living culture GMBCC 2338. Known distributions. China, Yunnan Province (Lu et al. 2025; Wanasinghe et al. 2025; this study). Known hosts. Coffea sp. (Lu et al. 2025), dead twigs of an unknown deciduous plant (Wanasinghe et al. 2025), Hevea brasiliensis (this study). Notes. Phylogenetic analyses show that strains GMBCC 2337 and GMBCC 2338 clustered with Pseudochaetosphaeronema baoshanense (MHZU 24–0566, holotype) and P. hongheense (KUNCC 23–16774; KUNCC 25–19456) with 99 % ML and 1.00 BI support (Fig. 1). Morphologically, the species isolated from Hevea brasiliensis is similar to the species described by Lu et al. (2025) from Coffea sp., in having cylindrical conidiogenous cells and yellowish to brown, oblong to ellipsoidal or fusoid conidia. However, the conidiomata wall of our samples (GMB-W 1227, GMB-W 1228) is thicker than the holotype of P. baoshanense (MHZU 24–0566) (50–60 μm vs. 20–40 μm), and conidia of our samples are sometimes slightly constricted at the septa, whereas in the holotype they are non-constricted. While the ITS, LSU, and SSU regions were identical between the new isolates (GMBCC 2337 and GMBCC 2337) and P. baoshanense (MHZU 24–0566), only the tef 1 - α gene region showed four base pairs differences. Based on the combined molecular evidence, our collections are identified as P. baoshanense. According to our knowledge, this is the first report of P. baoshanense on Hevea brasiliensis. Pseudochaetosphaeronema hongheense was introduced by Wanasinghe et al. (2025), and this fungus was isolated from Honghe, Yunnan Province. In the present study, P. hongheense (KUNCC 23–16774, KUNCC 25–19456) clusters with P. baoshanense (MHZU 24–0566, holotype) with 97 % ML support, but Bayesian support is low. Pairwise nucleotide comparisons showed no differences in ITS, LSU, and tef 1 - α sequences, with only a base-pair gap in SSU. Morphologically, P. hongheense (HKAS 146045, holotype) and P. baoshanense (MHZU 24–0566, holotype) are similar in conidiomatal structure, conidiogenous cells, and brown, septate conidia. However, P. baoshanense differs from P. hongheense in thicker conidiomatal wall (20–40 μm vs. 5–15 μm), conidia that are oblong to ellipsoidal or fusoid and not constricted at the septa, and in producing 1–3 - septate conidia that are only slightly thick-walled at maturity (Lu et al. 2025). Pseudochaetosphaeronema hongheense is characterized by distinctly constricted, consistently 3 - septate, thick-walled conidia (Wanasinghe et al. 2025). Based on the molecular and morphological evidence, P. hongheense is considered a synonym of P. baoshanense.