Pseudosetoseptoria jiangxiensis C.Y. Xu & D. M. Hu, 2024

Li, Cui, Xu, Chen-Yu, Hu, Dian-Ming, Tennakoon, Danushka S. & Song, Hai-Yan, 2024, Additions to Lentitheciaceae (Pleosporales, Dothideomycetes): Pseudosetoseptoria jiangxiensis sp. nov. from decaying culms of bamboo in China, Phytotaxa 668 (2), pp. 139-152 : 145-146

Pseudosetoseptoria jiangxiensis C.Y. Xu & D. M. Hu , sp. nov.

Index Fungorum number: IF902526; Facesoffungi number: FoF09317, FIGURE 2

Etymology:—Named after the place “ Jiangxi ” where the new taxa was collected.

Holotype:— HFJAU10184

Saprobic on submerged decaying bamboo culms in freshwater habitats. Sexual morph: Undetermined. Asexual morph: Coelomycetous. Conidiomata 350–850 × 400–650 µm (x̄ = 540 × 450 µm, n = 10), pycnidial, semi-immersed, dark brown to black, solitary or clustered, carbonaceous, covered with yellowish hypae, globose to subglobose, papillate. Conidiomatal wall 12–20 μm wide, composed of several layers of light brown to dark brown, cells of textura angularis, cells towards the inside lighter, at the outside darker and fusing with the host tissues. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 3–6 × 3–4.5 μm (x̄ = 4.2 × 3.6 µm, n = 10), hyaline, annallidic, cylindrical, slightly tapering towards apex and smooth-walled. Conidia 10.5–15 × 7–10.5 μm (x̄ =12.5 × 8.8 μm, n = 40), hyaline, broadly obovoid, elliptic, or nearly spherical, aseptate, minute guttulate, smooth-walled.

Culture characteristics:— Colonies on PDA, 13–15 mm diam. after 14 days at 25 °C, colonies from above: medium dense, circular, raised, cottony, surface smooth, entire margin, white to cream at margin, white to gray at center; reverse: white to yellowish at margin, light brown at center, Mycelium white to cream.

Material examined:— China, Jiangxi Province, Nanchang City, Nanyuan Village, on decaying bamboo culms, 19 March 2023, C.Y. Xu, slt-1-2 (HFJAU10184, holotype), ex-type living culture, JAUCC 6016 (other living cultures- JAUCC 6117, JAUCC 6194).

Notes:— Pseudosetoseptoria was introduced by Tian et al. (2024) to include Pse. oryzae (MFLUCC 23-0151) as the type species. According to the multi-gene phylogeny (LSU, SSU, ITS, tef1-α), our collection (JAUCC 6016, JAUCC 6194 and JAUCC 6117) groups with Pse. oryzae (MFLU 23-0176 and MFLU 23-0177) with 95% ML and 1.00 BYPP statistical support. In addition, the strains, JAUCC6016, JAUCC6194 and JAUCC6117 cluster together with 100% ML and 1.00 BYPP bootstrap support. Morphologically, our collection differs from Pse. oryzae in having semi-immersed, carbonaceous, large conidiomata (350–850 × 400–650 µm) and broadly obovoid, aseptate conidia, whereas Pse. oryzae has immersed, smaller conidiomata (45–145 × 50–150 µm) and ellipsoid to ovoid, 1-septate conidia ( Tian et al. 2024). In addition, our isolate differs from colony characteristics in having white to cream mycelia whereas Pse. oryzae has dark brown mycelia ( Tian et al. 2024). We compared the nucleotides across the ITS (+ 5.8S) gene region of our collection (JAUCC 6016) and Pse. oryzae (MFLUCC 23-0151). According to the results, there are 29 base pair differences (across 558 nucleotides). In addition, there were 34 base pair differences across the 911 nucleotides of tef1-α gene region and 10 base pair differences across the 838 nucleotides of LSU.

The asexual morph of Setoseptoria can be distinguished from our collection by brown, immersed conidiomata with verruculose to warty setae and hyaline or olivaceous, subcylindrical, transversely euseptate conidia with obtuse or subobtuse apex, truncate base and mostly with one large central guttule per cell ( Quaedvlieg et al. 2013). Conversely, our collection has brown to black, semi-immersed, carbonaceous conidiomata without setae and obovoid, elliptic, or nearly spherical, aseptate conidia with minute guttules. As well as, the apical region of conidiogenous cells in Setoseptoria has several inconspicuous percurrent proliferations, or with periclinal thickening, which were not observed in our collection ( Quaedvlieg et al. 2013). Therefore, based on both morphology and phylogeny evidence, we introduce our collection as a new species, Pseudosetoseptoria jiangxiensis from China.

Figures

FIGURE 2. Pseudosetoseptoria jiangxiensis (HFJAU10184, holotype) a Appearance of conidiomata on host. b Close up of conidioma. c Conidioma in squash mount. d,e,g Vertical sections through conidiomata (g Drawing of a vertical section of conidioma). f Conidiomatal wall. h–j Conidiogenous cells and developing conidia. k A germinated conidium. l–o Conidia. (on PDA). p Colony from above (on PDA). q Colony from below (on PDA). Scale bars: c–e,g = 200 µm, f = 15 µm, h–o = 10 µm.