Neoscytalidium hylocerei-undati S.S. Xiang & C.L. Yang [as ‘hylocereum-undulatum’], in Yang, Li, Xiang, Xu, Zeng, Sun, Liu, Maharachchikumbura, Lv, Wang, Ji-Zuo, A-Niu & Liu, Mycosphere 16(1): 1876 (2025)
Index Fungorum number: IF665049; MycoBank number: MB665049; Facesoffungi number: FoF16129
Etymology – The specific epithet reflects the host genus Hylocereus.
Holotype – SICAU 23-0144
Associated with canker on stems of Hylocereus undatus (Haw.) Britt. et Rose. Sexual morph: Not observed. Asexual morph: Coelomycetous. Conidiomata 95–120 × 95–180 μm (x̄ = 102 × 123 μm, n = 10), pycnidial, immersed to partly erumpent at maturity, brown to black, solitary, scattered, uni-loculate, ellipsoid or fusiform, ostiolate, glabrous. Conidiomatal wall 7–34 μm width, comprising of thick-walled, pale brown to brown cells of textura angularis, thickening at apical zone. Conidiophores reduced to conidiogenous cells, arising from the inner layer cells of the conidiomata. Conidiogenous cells 7–18 × 2–6 μm (x̄ = 10.2 × 3.5 μm, n = 30), hyaline, enteroblastic, monophialidic, integrated, cylindrical to subcylindrical, tapered to the apices, straight or curved, with minute collarette, smooth-walled, collarette 0.5–3 μm long. Conidia 11–17(–22) × 4.5–7 μm (x̄ = 14.4 × 5.7 μm, n = 50), hyaline, fusiform, ellipsoid, subcylindrical, straight or slightly curved, aseptate, usually with two guttules, thin-walled, smooth. Beta-conidia not observed.
Culture characteristics – Colonies on PDA attaining 60–70 mm diameter in 4 days, fastgrowing, circular, fimbriat, white, filamentous aerial mycelium superficially, reverse white.
Material examined – China, Sichuan Province, Chengdu City, Wenjiang District, Schoolyard of Sichuan Agricultural University, 103°51′27.55″E 30°42′19.5″N, 550 m, isol. from stems of Hylocereus undatus, 10 Nov. 2020, C.L. Yang, YCL202011003 (SICAU 23-0144, holotype), extype culture (SICAUCC 23-0103). ibid. YCL202011003-2 (SICAU 23-0151), living culture SICAUCC 23-0137.
GenBank numbers – SICAUCC 23-0103 = ITS: PP781969, LSU: PP719621, SSU: PP734052, tef1-α: PQ005620, tub2: PQ005626. SICAUCC 23-0137 = ITS: PP781970, LSU: PP719626, SSU: PP734054, tef1-α: PQ005623, tub2: PQ005627
Notes – In the phylogenetic analysis, Neoscytalidium hylocerei-undati forms a well-supported subclade within Neoscytalidium (96% MLBS / 1.00 BYPP) and shows a close relationship with N. hylocereum. Through pairwise nucleotide comparisons, N. hylocerei-undati exhibits distinctions from N. hylocereum (TSU-HP01, holotype). The ITS region shows a 98.0% similarity (496/506, 2 gaps), tef1-α shows 96.8% similarity (245/253, 0 gap), and tub2 is 100% identical (400/400, 0 gap). Morphologically, N. hylocerei-undati sets itself apart from N. hylocereum by having larger conidia (11–17(–22) × 4.5–7 μm vs. 9.8–13.5 × 3.7–5 µm) and a more rapid colony growth rate (15–17.5 mm/d vs. 30 mm/d). Furthermore, N. hylocerei-undati features two guttules on conidia, a characteristic absent in N. hylocereum (Wonglom et al. 2023). Consequently, we introduce N. hylocerei-undati as a distinct and novel species.
Figure 1 – Neoscytalidium hylocerei-undati (SICAU 23-0144). a, b Symptoms on the leaf. c Conidiomata. d Conidiogenous cells. e Conidiogenous cells with immature conidia. f Conidia. g Germinated conidium. h, i Colonies on PDA. Scale bars: c = 50 μm, d = 20 μm, e–g = 10 μm.