Pseudochaetosphaeronema xishuangbannaense R. F. Xu & Tibpromma

Pseudochaetosphaeronema xishuangbannaense R. F. Xu & Tibpromma, MycoKeys 103: 71–95 (2024) [as ‘ xishuangbannaensis’] Fig. 5 Description. Saprobic on a decaying branch of Hevea brasiliensis. Sexual morph: Ascomata 110–330 × 212–335 μm, (x ̄ = 218 × 263 μm, n = 10), white spot on the surface, sometimes inconspicuous on host surface, solitary, scattered, immersed, globose to subglobose or pyiform, or ellipsoid, uni-loculate, brown, with ostiole. Ostiole 70–155 × 60–85 μm, (x ̄ = 105 × 70 μm, n = 5), central, brown, papillate. Peridium 30–60 μm wide, composed of several layers, brown to pale brown to hyaline cells of textura intricata. Hamathecium comprises 2–3 μm wide, numerous, filiform, unbranched, hyaline, cellular pseudoparaphyses. Asci 80–110 × 16–30 μm (x ̄ = 95 × 21 μm, n = 15), 8 - spored, bitunicate, obovoid, short, distinct pedicel, apex rounded with an ocular chamber. Ascospores 26–36 × 10–12 μm (x ̄ = 30 × 11 μm, n = 20), hyaline, fusiform, with pointed ends, 1 - septate, occasionally 3 - septate, constricted at the middle septum, wider upper cell, constricted at the septa, guttulate, thick-walled, with a thin mucilaginous sheath. Asexual morph: Undetermined. Culture characteristics. Ascospores germinate on PDA within 24 hours. Colonies circular, umbonate, entire margin; brown from above, dark brown at center and edge, with brown ring on reverse. 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 42 (GMB-W 1226), living culture GMBCC 2336. Known distributions. China, Yunnan Province, Xishuangbanna Dai Autonomous Prefecture (Xu et al. 2024), China, Yunnan Province, Dehong Dai and Jingpo Autonomous Prefecture (this study). Known hosts. Hevea brasiliensis (Xu et al. 2024, this study) Notes. In the phylogenetic analyses, strain GMBCC 2336 formed a clade with strains of P. xishuangbannaense (ZHKUCC 23–0804 and ZHKUCC 23–0805) with 100 % ML / 1.00 BYPP statistical supports (Fig. 1). Compared with the holotype of P. xishuangbannaense (ZHKU 23–0107) with our sample (GMB-W 1226) has smaller ascomata (110–330 × 212–335 μm vs. 270–410 × 370–480 μm), a thinner peridium (30–60 μm vs. 40–90 μm), smaller asci (80–110 × 16–30 μm vs. 130–180 × 25–35 μm), and smaller, 1–3 - septate ascospores (26–36 × 10–12 μm vs. 30–50 × 10–20 μm, 3–5 - septate) (Xu et al. 2024). Despite these size differences, the overall morphology and phylogeny align with those of P. xishuangbannaense. The nucleotide comparisons show differences of 3 bp (570 bp) and 1 bp (954 bp) of ITS and SSU, respectively, between the new isolate (GMBCC 2336) and the ex-type of P. xishuangbannaense (ZHKUCC 23–0804). Therefore, strain GMBCC 2336 is identified as P. xishuangbannaense and represents a newly collected specimen from Dehong, about 415 km from the type locality in Xishuangbanna.