Pseudosetoseptoria 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): 46 (2024)

Index Fungorum Number: IF 900974; MycoBank Number: MB 900974; Facesoffungi Number: FoF 14287

Etymology – Referring to its similarity with Setoseptoria.

Saprobic on dead leaves or wood in terrestrial habitats. Sexual morph: Not observed. Asexual morph: Coelomycetous. Conidiomata pycnidial, immersed, solitary, scattered, visible as black spots on host surface, globose to subglobose, brown to dark brown. Conidiomata wall thin, composed of 2–4 layers of brown cells of textura angularis. Hamathecium not observed. Conidiophores reduced to conidiogenous cells. Conidiogenous cells lining the inner cavity in basal layer, holoblastic, hyaline, subcylindrical to ampulliform, smooth, forming conidia at their tips. Conidia hyaline, smooth, 1-septate, ellipsoid to ovoid with both ends rounded, guttulate, thick-walled.

Type species – Pseudosetoseptoria oryzae X.G. Tian, K.D. Hyde & Tibpromma

Notes – In the multi-loci phylogenetic analyses, our strains (MFLUCC 23-0151 and MFLUCC 23-0131) clustered together within Lentitheciaceae, sister to Setoseptoria species with 60 ML and 0.98 PP statistical support (Fig. 1). Morphologically, Setoseptoria is different from Pseudosetoseptoria in having conidiomata with verruculose to warty setae, collarette inconspicuous, or prominent conidiogenous cells and subcylindrical, multi-euseptate conidia which are tapering in apical part to obtuse or subobtuse apex, base truncate. In contrast, the conidiomata of Pseudosetoseptoria lacking setae, conidiogenous cells are subcylindrical to ampulliform, and conidia are 1-septate, ellipsoid to ovoid with round ends. In addition, the apical region of conidiogenous cells in Setoseptoria is several inconspicuous percurrent proliferations or periclinal thickening, which were not observed in Pseudosetoseptoria (Quaedvlieg et al. 2013).

Figure 1 – Phylogram generated from maximum likelihood analysis based on combined ITS, LSU, SSU, and tef1-α sequence data. Related sequences were obtained from Liu et al. (2021c). Sixty-nine strains are included in the combined sequence analysis, which comprise 4143 characters with gaps. Helminthosporium velutinum (MAFF 243854) and Massarina eburnean (CBS 473.64) were used as the outgroup taxa. Tree topology of the ML analysis was similar to the PP. The best scoring RAxML tree with a final likelihood value of 23713.546172 is presented. The matrix had 1310 distinct alignment patterns, with 32.08% of undetermined characters or gaps. Estimated base frequencies were as follows; A = 0.239761, C = 0.247852, G = 0.272034, T = 0.240353; substitution rates AC = 1.298345, AG = 2.459949, AT = 1.275662, CG = 1.232515, CT = 6.803258, GT = 1.000000; gamma distribution shape parameter α = 0.171406. Bootstrap support values for ML equal to or greater than 60% and PP equal to or greater than 0.90 are given above the nodes. Newly generated sequences are in red, while T indicates holotype or ex-type strains.