Neocosmospora phalaenopsidis S.S. Xiang & C.L. Yang, in Yang, Li, Xiang, Xu, Zeng, Sun, Liu, Maharachchikumbura, Lv, Wang, Ji-Zuo, A-Niu & Liu, Mycosphere 16(1): 1966 (2025)

Index Fungorum number: IF900695; MycoBank number: MB900695; Facesoffungi number: FoF16130

Etymology – Refers to the host genus Phalaenopsis.

Holotype – SICAU 23-0140

Associated with rachis blight on the rachis of Phalaenopsis aphrodite Rchb. F. Sexual morph: Not observed. Asexual morph: Hyphomycetous. Conidiophores 81–124 × 2–4 μm (x̄ = 106 × 3 μm, n = 30), aggregated in dense fascicles, arising from the upper cells of stroma, erumpent, subcylindrical, straight to variously curved, hyaline, unbranched or branched once or twice, septate, smooth, thin-walled; each branch terminating in a single phialide, tapering uniformly from base to tip, collarette of phialides thickened, not conspicuously flared. Conidia typically arising from conidiophore or sporodochia, hyaline, thin-walled, smooth. Alpha-conidia 7–18 × 4–6 μm (x̄ = 11 × 4.9 μm, n = 50), ellipsoidal, aseptate. Beta-conidia 15–39 × 4–6 μm (x̄ = 28 × 5 μm, n = 50), falcate, tapering uniformly to a subacute tip, 1–3–septate. Chlamydospores unicellular, ovoid to ellipsoidal, single or in chains, terminal on hyphae or intercalary, pale brown in colour, consisting of enlarged, thick-walled vegetative cells: unicellular 8–9.5 × 7–9 μm (x̄ = 8.8 × 8.0 μm, n = 50); multicellular 13–37 × 7–12 μm (x̄ = 20 × 8.3 μm, n = 50).

Culture characteristics – Colonies on MEA attaining 40–45 mm diameter in 20 days, colony surface greyish white, aerial mycelium white, cottony and more densely formed at the colony center becoming flat towards the margin, reverse yellow at the center fading to brown at the margin. Colony margin entire to undulate. Colonies on OA attaining 40–45 mm diameter in 70 days, colony surface white, aerial mycelium white, flocculent, reverse overall white with irregular yellow to brown pigmented areas. Colonies on PDA attaining 40–45 mm diameter in 20 days, medium sparse, irregular, hairy edge, colony surface white, aerial mycelium white, cottony, reverse white. Colonies on SNA attaining 40–45 mm diameter in 70 days, sparse, irregular, hairy edge, colony surface white, aerial mycelium white, well developed in the middle, sparse at the margin, reverse white.

Material examined – China, Sichuan Province, Chengdu City, Wenjiang District, 103°51′14.06″E 30°42′35.25″N, 537 m, isol. from the rachis of Phalaenopsis aphrodite, 20 Nov. 2020, C.L. Yang, YCL202011005 (SICAU 23-0140, holotype), ex-type culture (SICAUCC 23- 0104). ibid., YCL202011005-2 (SICAU 23-0166), living culture SICAUCC 23-0138.

GenBank numbers – SICAUCC 23-0104 = ITS: PP769690, LSU: PP719622, tef1-α: PQ005621, rpb2: PQ005613, PQ005614. SICAUCC 23-0138 = ITS: PP769694, LSU: PP719627, tef1-α: PQ005624, rpb2: PQ005615, PQ005616

Notes – Our strain, as revealed by multigene analyses encompassing ITS, LSU, rpb2, and tef1-α sequence data, forms a cluster with Neocosmospora solani, albeit with low bootstrap support. In the context of sequence comparisons with N. solani (CBS 140079), notable differences emerge. The rpb2 fragments show similarity levels of 97.75% (781/799, 0 gap) and 98.13% (839/855, 0 gap), while the tef1-α fragment is 98.03% (698/712, 3 gaps), the ITS fragment is 99.12% (561/566, 1 gap), and the LSU fragment is 99.83% (598/599, 0 gap) (Schroers et al. 2016). Morphologically, N. phalaenopsidis is different from N. solani in having smaller conidia (15–39 × 4–6 μm vs. 8.5–53 × 2.5–7) and fewer conidial septa (0–3 septa vs. 0–5 septa), and the colony growth rate of N. phalaenopsidis is slower than that of N. solani (on PDA: 2.0–2.3 mm/d vs. 6.5– 8.5 mm/d; on SNA: 0.6 mm/d vs. 8–9 mm/d) (Schroers et al. 2016). The PHI test also showed no significant recombination events between N. solani and N. phalaenopsidis. Therefore, we introduce N. phalaenopsidis as a new species.

Figure 1 – Neocosmospora phalaenopsidis (holotype, SICAU 23-0140). a Symptoms on the rachis. b, c Appearance of conidiogenesis. d, e Fascicles with conidiophores and conidiogenous cells. f Conidiophores bearing conidia. g Conidia. h Front and reverse view of colonies on MEA. i, j Conidiophores bearing conidia on MEA. k Conidia on MEA. l Front and reverse view of colonies on OA. m, n Conidiophores bearing conidia on OA. o Chlamydospore on OA. p Conidia on OA. q Front and reverse view of colonies on PDA. r, s Conidiophores bearing conidia on PDA. t Chlamydospore on PDA. u Conidia on PDA. v Front and reverse view of colonies on SNA. w, x Conidiophores bearing conidia on SNA. t Chlamydospore on SNA. u Conidia on SNA. Scale bars: b = 190 μm, c = 40 μm, d, e = 20 μm, f–g, i–k, m–p, r–u, w–z = 10 μm.