Clonostachys yadongensis S. C. He, K. D. Hyde & Q. Zhao 2025, sp. nov.

Clonostachys yadongensis S. C. He, K. D. Hyde & Q. Zhao sp. nov. Fig. 4 Etymology. The species epithet is derived from Yadong County, where the holotype was collected. Typification. China • Xizang Autonomous Region, Linzhi City, Yadong County (27°48'N, 88°83'E, 3894 m), on the lower part of the leaves of Ageratina adenophora leaves, July 24, 2023, collected by Shu-Cheng He, HSC 1025 (holotype: KUN-HKAS 133183); ex-type living culture: KUNCC 24-18532). GenBank: ITS: PQ 522508, 28 S: PQ 634395, tef 1: PQ 650481, tub 2: PQ 650463, rpb 2: PQ 538524. Description. Sexual morph: Not observed. Asexual morph: Hyphomycetous. Colonies on the WA, solitary or gregarious, white to pale yellow, raised, medium sparse, rough. Conidiophores mononematous, penicillate, straight or flexuous, branched, smooth-walled, thin-walled, septate, hyaline, produce globose cells at the apex, terminal branches developing into phialides, 80–118 × 2.4–3.4 μm (x ̄ = 97 × 2.8 μm, n = 20). Phialides polyblastic, terminal, flask-shaped, aseptate, hyaline, smooth, thin-walled, minutely guttulate, terminal developing into conidia, 9.6–15.6 × 1.7–2.3 μm (x ̄ = 13.1 × 2 μm, n = 20). Conidia amerospores, solitary, acrogenous, simple, oval to ellipsoidal, smooth, thin-walled, aseptate, hyaline, minutely guttulate, 3.6–5.4 × 2.6–3.3 μm (x ̄ = 4.5 × 2.9 μm, n = 30). Culture characteristics. Colonies on PDA reaching 5.5–6 cm after 20 days of incubation at 25 ° C, white above, pale yellow reverse, medium spare, raised, hairy, fimbriate, velvety, ciliate, not pigment produced. Habitat. Leaves of Ageratina adenophora. Additional material examined. China • Xizang Autonomous Region, Linzhi City, Yadong County (27°48'N, 88°83'E, 3894 m), on the lower part of the leaves of Ageratina adenophora, July 24, 2023, collected by Shu-Cheng He, HSC 1025 A (isotype: KUN-HKAS 133184; ex-isotype living culture: KUNCC 24-18533). GenBank: ITS: PQ 522509, 28 S: PQ 634391, tef 1: PQ 650482, tub 2: PQ 650464, rpb 2: PQ 538525. Notes. In the phylogenetic analysis, Clonostachys yadongensis clustered with C. krabiensis with 100 % MLB and 0.91 BYPP support (Fig. 1). Clonostachys krabiensis was introduced by Tibpromma et al. (2018) and is characterized by solitary, superficial, globose to subglobose, orange to brownish orange ascomata, 6–8 - spored, cylindrical to clavate asci; fusoid to ellipsoidal, hyaline, with longitudinal striations, granulate ascospores. Its morphology fits well with the generic concept of Clonostachys sexual morph (Bao et al. 2023; Perera et al. 2023; Zhao et al. 2023). Our specimen (HKAS 133183) exhibited an asexual morph that is characterized by mononematous, penicillate, erect conidiophores; flask-shaped or cylindrical, aseptate, hyaline phialides; acrogenous, ellipsoidal or oblong with obtuse ends, hyaline conidia. The 28 S and ITS sequences of Clonostachys yadongensis differ from that of C. krabiensis which showed base pair differences, 3 / 825 (0.35 %), 11 / 513) and (2.1 %) respectively. Clonostachys krabiensis was reported in Papua New Guinea and Thailand as a saprobe on Pandanus sp. and wood litter, while C. yadongensis was reported in the Xizang Autonomous Region, China, mainly as an endophyte on Ageratina adenophora. Clonostachys krabiensis has been reported to have a sexual morph, but C. yadongensis has only been observed in its asexual morph. Based on base pair differences and following the guidelines of Maharachchimbukura et al. (2021), we identified our specimen as a new species, Clonostachys yadongensis.