Pseudosetoseptoria oryzae X.G. Tian, K.D. Hyde & Tibpromma, in Tian, Bao, Karunarathna, Jayawardena, Hyde, Bhat, Luo, Elgorban, Hongsanan, Rajeshkumar, Maharachchikumbura, Suwannarach, Dawoud, Lu, Han, Xiao, Du, Lu, Xu, Dai, Liu, Liu & Tibpromma, Mycosphere 15(1): 47 (2024)
Index Fungorum number: IF 900975; Facesoffungi number: FoF 14288
Etymology – Referring to the host plant Oryza sativa, on which the fungus was collected.
Holotype – MFLU 23-0177
Saprobic on leaves of Oryza sativa. Sexual morph: Not observed. Asexual morph: Coelomycetous. Conidiomata pycnidial, 45–145 × 50–150 µm (x̅ = 97 × 100 µm, n = 10), immersed, solitary, scattered, visible as black spots on host surface, globose to subglobose, brown to dark brown. Conidiomata wall 8–20 µm (x̅= 12 µm, n = 15), thin, composed of 2–4 layers of brown textura angularis. Paraphyses not observed. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner cavity in basal layer, annallidic, hyaline, subcylindrical to ampulliform, smooth, forming conidia at their tips. Conidia 10–20 × 7.5–9 µm. hyaline, smooth, 1-septate, ellipsoid to ovoid, rounded at both ends, guttulate, thick-walled.
Culture characteristics – Colonies on PDA reaching 20 mm diameter after two weeks at 25 °C. Colonies on PDA filamentous margins, flat, superficial, circular, smooth or folded surface, superficial and reverse dark brown.
Material examined – Thailand, Chiang Rai Province, Mueang District, Subdistrict, on dead leaves of Oryza sativa, 3 January 2021, X.G. Tian, r8-1 (MFLU 23-0177, holotype), ex-type culture MFLUCC 23-0151; ibid, 10 November 2020, X.G. Tian, r6-5 (MFLU 23-0176, paratype), ex-paratype living culture MFLUCC 23-0131.
GenBank numbers – MFLUCC 23-0151: LSU = OR438823, ITS = OR438352, SSU = OR458343. MFLUCC 23-0131: LSU = OR438822, ITS = OR438351, SSU = OR458342, tef1-α = OR500315.
Notes – In the multi-loci phylogenetic analyses, our strains (MFLUCC 23-0151 and MFLUCC 23-0131) clustered within Lentitheciaceae, sister to Setoseptoria. In a BLASTn search of NCBI GenBank, the closest match in Lentitheciaceae with the ITS sequences of Pseudosetoseptoria oryzae (MFLUCC 23-0131) with 99.31% similarity to Setoseptoria sp. (GZCC 19–0487). The closest match with the LSU sequences with 98.11% similarity to S. magniarundinacea (HHUF 28293). The closest match of the SSU sequence with 100% similarity to Phragmocamarosporium hederae strain KUMCC 18-0166, Keissleriella caraganae strain KUMCC 18-0164, Murilentithecium clematidis strain MFLUCC 14-0562, and S. phragmitis strain GZCC 19-0485. The closest match with the tef1-α sequences with 96.47% similarity to S. arundinacea strain HHUF 27543. The PHI test revealed no significant recombination event between Pseudosetoseptoria oryzae and the closely related taxa (Φw = 0.99) (Fig. 30). The significant recombination between two strains of Pseudosetoseptoria oryzae (MFLUCC 23-0151 and MFLUCC 23-0131) indicates that they are conspecific.
Figure 1 – Pseudosetoseptoria oryzae (MFLU 23-0177, holotype). a, b Appearance of conidiomata on the host. c, d Section through conidioma. e, f, h Conidiogenous cells and developing conidia. g Section of peridium. k–o Conidia. i Germinated conidium. j, p Colonies on PDA from surface and reverse. Scale bars: c, d = 50 μm, e, g–i = 20 μm, f, k–o = 10 μm.