Pseudochaetosphaeronema chiangraiense Wijesinghe, Boonmee & K. D. Hyde

Pseudochaetosphaeronema chiangraiense Wijesinghe, Boonmee & K. D. Hyde, Fungal Diversity 111: 75 (2021) Fig. 3 Description. Saprobic on a decaying branch of Hevea brasiliensis. Sexual morph: Ascomata 170–280 × 200–280 μm (x ̄ = 221 × 223 μm, n = 10), solitary, scattered, immersed, uniloculate, globose to subglobose. Peridium 30–50 μm wide, composed of several brown to pale brown cells of textura angularis. Hamathecium 1–2 μm wide, numerous, filiform, unbranched, pseudoparaphyses. Asci 80–123 × 23–29 μm (x ̄ = 99 × 25 μm, n = 15), 8 - spored, bitunicate, fissitunicate, cylindrical to clavate, with a short pedicel, apex rounded, with ocular chamber. Ascospores 20–32 × 7–13 μm (x ̄ = 26 × 10 μm, n = 30), overlapping, 2–3 seriate, fusiform, with obtuse ends, 1 - septate at the center, constricted at the septa, hyaline, guttulate, thick and smooth-walled. Asexual morph: Undetermined. Culture characteristics. Ascospores germinated on PDA within 24 hours, and ascospores turned brown after germination. Colonies irregular, wrinkled, brown, crateriform with undulate margin; reverse dark brown. 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 30 (GMB-W 1225), living culture GMBCC 2335. Known distributions. Thailand (Boonmee et al. 2021) and Yunnan Province, China (Li et al. 2023; this study). Known hosts. Tamarindus sp. (Boonmee et al. 2021), Olea europaea (Li et al. 2023), and Hevea brasiliensis (this study). Notes. Pseudochaetosphaeronema chiangraiense was collected from Tamarindus sp. in Chiang Rai, Thailand (Boonmee et al. 2021), and was also later recorded on Olea europaea in Sichuan Province, China (Li et al. 2023). In this study, our isolate (GMBCC 2335) was grouped with P. chiangraiense (MFLUCC 21–0083, ex-type). The morphology of our collection (GMB-W 1225) is similar to the holotype of P. chiangraiense (Boonmee et al. 2021), but differs only in size: holotype with a thinner peridium when compared to our collection (13–17 μm vs. 30–50 μm), and a bit big in pseudoparaphyses (2–4.5 μm vs. 1–2 μm); larger asci (50–110 × 15–30 μm vs. 80–123 × 23–29 μm), and longer ascospores (20–45 μm vs. 20–32 μm). However, the new isolate was genetically identical to P. chiangraiense in the ITS, LSU, and SSU regions but differed by three base pairs in the tef 1 - α gene. Therefore, we identify our strain as P. chiangraiense based on phylogenetic and morphological evidence. According to our knowledge, this is the first record of P. chiangraiense on H. brasiliensis in China.