Helminthosporium puerensis L. Lu & Tibpromma 2025, sp. nov.

Helminthosporium puerensis L. Lu & Tibpromma sp. nov. Fig. 12 Etymology. The epithet refers to the location “ Pu’er “ from where the holotype was collected. Diagnosis. Differs from H. quercinum Voglmayr & Jaklitsch and H. microsorum D. Sacc., by the hyaline ascospores with inconspicuous sheath. Holotype. HKAS 137606. Description. Saprobic on decaying branch of C. arabica. Teleomorph: Ascomata 250–400 × 220–400 µm (x- = 320 × 310 µm, n = 15, including ostioles), solitary to scattered, immersed, visible as black dots with black hair on the host surface, globose to subglobose. Ostiolar neck central, cylindrical to papillate, surrounded by dark brown clypeus-like structure, without periphyses. Peridium 20–30 µm wide (x- = 26, n = 20), composed of 4–6 layers of textura angularis cells, polygonal to rectangular, light brown. Hamathecium 2–3 µm wide (x- = 2.2, n = 20), hyaline, filiform, branched, septate, pseudoparaphyses numerous. Asci 80–170 × 15–25 µm (x- = 130 × 19 µm, n = 20), 4–8 - spored, fissitunicate, bitunicate, clavate, straight, rounded at the apex, with a narrow apical chamber and faint ring, short-stalked with club-shape, sometimes with long stipes. Ascospores 25–30 × 7–11 µm (x- = 26.5 × 9 µm, n = 30), mostly straight, 1–3 - septate, constricted at the septum, asymmetric, with wider upper cell, hyaline, guttulate, smooth-walled, sheath present. Anamorph: Not observed. Culture characteristics. Ascospores germinating on PDA within 12 h, colonies reached 4 cm in diameter after two months at 25 ° C, surface smooth, circular, flat, with entire margin, from above, hyaline to light yellow, from below, dark brown at the centre, hyaline at the margin. Materials examined. China, Yunnan Province, Pu’er, on a decaying branch of Coffea arabica (Rubiaceae) (22°70'12"N, 101°34'78"E, 900 m alt.), 6 September 2020, LiLu, QX-C 7 (HKAS 137606, holotype), isotype MHZU 23-0055, ex-type living culture KUNCC 24-18347 = KUNCC 24-18348, ex-isotype living culture ZHKUCC 23-0620 = ZHKUCC 23-0621. Notes. Phylogenetic analyses show that Helminthosporium puerensis groups with H. chinense Y. P. Chen & Maharachch., (CGMCC 3.23570) and H. nanjingense Meng Zhang, Xiao J. Wang & H. Y. Wu, (HHAUF 020380) (Fig. 13). Helminthosporium chinense and H. nanjingense were only reported as anamorphs from decaying branches of palm trees (Sichuan Province, China) and dead branches of an unidentified tree (Jiangsu Province, China), respectively. Based on nucleotide comparisons, H. puerensis (ZHKUCC 23-0620) is different from H. chinense (CGMCC 3.23570) by 18 / 578 bp (3 %, without gaps) of the ITS, 3 / 749 bp (0.4 %, without gaps) of the LSU, 16 / 780 bp (2 %, without gaps) of the SSU and 8 / 320 bp (2.5 %, without gaps) of the TEF 1 - α. In comparison, it is different from H. nanjingense (HHAUF 020380) in 7 / 454 bp (1.5 %, without gaps) of the ITS (H. nanjingense only has ITS sequence data available). Helminthosporium chinense and H. nanjingense showed only a small difference in ITS by 7 / 447 (1.6 %, without gaps). Based on BLASTn search results of sequence data, ITS is 97.4 % similar to H. chinense (ON 557754), LSU, SSU and RPB 2 are closely related to H. quercinum, with similarity rates of 97 % (KY 984338), 98.8 % (NG _062196) and 92.5 % (KY 984398), respectively and TEF 1 - α is 94 % (KY 984448) similar to H. microsorum. In terms of morphological characteristics, our species can be distinguished from H. quercinum and H. microsorum by the hyaline ascospores with inconspicuous sheath; H. quercinum and H. microsorum are hyaline to brown ascospores with conspicuous sheath (Voglmayr and Jaklitsch 2017). Our species is most similar to the teleomorph H. massarinum in that it has ellipsoidal and hyaline ascospores (Fig. 12; Tanaka et al. (2015)). In addition, the PHI test results (Fig. 22 f) revealed no significant recombination relationships between H. puerensis and its phylogenetically related taxa. Therefore, the morphological differences and phylogenetic analyses support the introduction of H. puerensis as a new species.