Dothiorella fusiformis Rathnayaka & F. Q. Yu 2026, sp. nov.

Dothiorella fusiformis Rathnayaka & F. Q. Yu sp. nov. Figs 3, 4 Etymology. The epithet refers to fusiform-shaped ascospores. Holotype. HKAS 151748. Description. Saprobic on dead twigs of Thalictrum sp. Sexual morph: Ascomata 190–250 μm high × 190–225 μm diam. (x ̄ = 220 × 200 μm, n = 10), immersed to erumpent through host tissue, globose, solitary and scattered, black, unilocular. Peridium 20–35 μm wide, composed of two layers, outer layer consists of thick-walled, dark brown to brown cells of textura angularis, inner layer composed of thin-walled, pale brown to hyaline cells of textura angularis. Hamathecium comprising numerous 3–5 μm wide, hyaline, septate, unbranched pseudoparaphyses. Asci 80–91 × 17–20 μm (x ̄ = 87 × 19 μm, n = 30), 8 or 4 - spored, bitunicate, fissitunicate, cylindrical-clavate to clavate, short-pedicellate, apically rounded, with ocular chamber. Ascospores 13–18 × 6–10 μm (x ̄ = 16 × 5 μm, n = 30), length / width (l / w) ratio = 3.2, overlapping 2–3 - seriate, broadly fusiform, straight or slightly curved, initially hyaline and aseptate, becoming dark brown and 1 - septate at maturity, slightly constricted at the septum, rough-walled. Asexual morph: Saprobic on the dead twigs of Thalictrum sp. Coelomycetous. Conidiomata 295–325 μm high × 310–375 μm diam. (x ̄ = 310 × 350 μm, n = 10), pycnidial, solitary, globose, formed in uniloculate stromata, immersed to erumpent through host tissue. Conidiomatal wall 20–38 μm diam., 4–6 layers, consists of outer layers of thick-walled, dark brown to brown cells of textura angularis, inner layers consists of thin-walled, pale brown to hyaline cells of textura angularis. Conidiophores usually reduced to conidiogenous cells. Conidiogenous cells 10–4 μm high × 3–5 μm diam. (x ̄ = 6 × 4 μm, n = 15), lining the pycnidial cavity, holoblastic, hyaline, cylindrical, discrete, determinate, smooth-walled. Conidia 10–18 × 5–7 μm (x ̄ = 15 × 6 μm, n = 25, l / w = 2.5), oblong to ellipsoidal, straight or slightly curved, rounded at both ends, initially hyaline and aseptate, becoming dark brown often while attached to conidiogenous cell, slightly constricted at the septum, guttulate. Culture characteristics. Ascospores germinating on PDA within 24 h. Germ tubes produced at one side of ascospore. Colonies on PDA reaching 3–3.5 cm diam. after 4 days at 25 ° C, colonies circular in shape, medium dense, flat or effuse, slightly raised, fluffy to fairly fluffy, aerial, white in middle and black in outer layer in both upper and lower sides (Fig. 3). Conidia germinating on PDA within 24 h. Germ tubes produced at one side of Conidia. Colonies on PDA reaching 2–3.5 cm diam. after 5 days at 25 ° C, colonies circular in shape, medium dense, flat or effuse, slightly raised, fluffy to fairly fluffy, aerial, black in both upper and lower sides (Fig. 4). Material examined. China • Yunnan Province, Pu’er City, Xiaoheijiang Forest Park, lives on dead twigs of Thalictrum sp. (Ranunculaceae), 25 September 2025, Achala Rathnayaka, AS 80 (HKAS 151748, holotype), ex-type living culture GBWSCCF 120274; ibid., AS 82 (HKAS 151752), living culture GBWSCCF 120275. Notes. In the multi-gene phylogeny of combined LSU, ITS, tef 1 - α and β-tubulin analyses, our novel strains (GBWSCCF 120274 / HKAS 151748 / GBWSCCF 120275 / HKAS 151752) formed a separate clade sister to D. alpina (CGMCC 3.18001) with 94 % ML bootstrap and 0.98 PP support (Fig. 1, Group A). When comparing the basepair (bp) differences between our new isolate (HKAS 151748) and D. alpina (CGMCC 3.18001), ITS shows around 2.1 % (10 / 478) differences (without gaps). Also, bp comparison between HKAS 151748 / GBWSCCF 120274 and HKAS 151752 / GBWSCCF 120275 revealed that 0.2 % (1 / 490) and 0.1 % (1 / 852) differences in the ITS and LSU, respectively. Phylogenetically closely related Dothiorella alpina, has been recorded only from its asexual morph by Hyde et al. (2020) in Ipomoea sp., Yunnan Province, China. Morphologically, the asexual morph of our new collection (HKAS 151752) differs from D. alpina (KUN- HKAS 102212) by the size of conidiomata (295–325 μm high × 310–375 μm diam. vs. 135–245 µm high × 150–235 μm diam.) (Hyde et al. 2020). In considering the conidial morphology, D. fusiformis has oblong to ellipsoidal, straight or slightly curved conidia that slightly constricted at the septum, guttulate and with l / w ratio of 2.5 (this study). However, in D. alpina, the conidia are oblong, occasionally irregular in shape, not constricted at the septa, and with l / w ratio of 2.19 (Hyde et al. 2020). Thus, based on distinct morphology and phylogenetic evidence, we established our new collection, D. fusiformis as a new species in Dothiorella. Also, in this study, we introduced both sexual (GBWSCCF 120274 / HKAS 151748) and asexual (GBWSCCF 120275 / HKAS 151752) morphs of D. fusiformis.