Phaeoseptoriella poaceicola Y. Gao, H. Gui & K.D. Hyde, sp. nov.

Index Fungorum number: IF 902470; MycoBank number: MB 902470; Facesoffungi Number: FoF16260

Etymology – in reference to the holotype occurring on grasses (Poaceae)

Holotype – HKAS 128741

Saprobic on decaying stem of Dactylisglomerata (Poaceae). Sexual morph: Undetermined. Asexual morph: Conidiomata 60–75 μm high × 90–100 μm diam. (x̅ = 70 × 97 μm, n = 15), flattened, solitary, immersed in the epidermis of the host, globose to subglobose, brown to black spots. Conidiomatal wall 5.5–13 µm wide (x̅ = 9.5 μm, n = 25), thin-walled, 1–4 layered, composed of pale brown cells of textura angularis, with inner layer comprising hyaline cells. Conidiogenous cells (4.1–)4–7.7(–9.1) × (4–)4.3–5.7(5.5) μm (x̅ = 5.9±1.82 × 5±0.70 μm, n = 25), hyaline, globose to subglobose, smooth-walled. Conidia (30–)33–39(–41) × (4.3–)5–6(–6.7) μm (x̅ = 36±3.23 × 5.5±0.56 μm, n = 35), phragmosporous, initially hyaline, becoming pale yellowish at maturity, 7-septate, cylindrical to subcylindrical, straight or slightly curved, smooth-walled, rounded at apex, slightly truncate at base, guttulate.

Culture characteristics – Colonies on PDA, reaching 10–20 mm diam., after three weeks at 25–27 °C, with irregular, floccose, raised, white from the above and in reverse yellow.

Material examined – China, Yunnan Province, Zhaotong City (27°38’37″N, 103°37’5″E), on decaying stem of Dactylis glomerata (Poaceae), 25 September 2022, Ying Gao, LG7A (HKAS 128741, holotype), ex-type (CGMCC 3.24561); ibid., LG7B (HKAS 128742, paratype), ex-paratype (CGMCC 3.24562); ibid., on decaying stems of Anaphalis tenuisissima, 20 August 2021, Ying Gao, living cultures ZY356B (CGMCC 3.25058), ZY359A (CGMCC 3.25059), ZY359B (CGMCC 3.25060).

Note – Phaeoseptoriella poaceicola is introduced as a new species based on morphology and phylogenetic analysis of combined SSU, LSU, ITS, tef1-α, and rpb2 datasets. Our strains of Phaeoseptoriellapoaceicola (CGMCC 3.24561, CGMCC 3.24561, CGMCC 3.25058, CGMCC 3.25059, and CGMCC 3.25060) distinct clade (100% ML, 1.00 PP, Clade C). The ITS pairwise nucleotide comparison of our isolate Phaeoseptoriella poaceicola (CGMCC 3.24561) with Phaeoseptoriella edithcowaniae (PP707905), Ph. emmelinepankhurstiae (OR673891), Ph. vidagoldsteiniae (OR673892), and Ph. zeae (NR_163371) showed 123/601 bp, 83/537 bp, 81/537 bp, and 88/534 bp differences (20.47%, with 37 gaps; 15.46%, with 27 gaps; 15.08%, with 25 gaps; 16.48%, with 28 gaps), respectively. Our isolate differs from Ph. edithcowaniae (PP708933) and Ph. zeae (NG_067869) in 13/836 bp and 4/836 (1.56% and 0.48% without gaps) in the LSU regions, respectively. It differs from Ph. zeae (MK442674) in 130/878 bp (14.81%, without gaps) in the rpb2 regions, SSU and tef1-α of other Parastagonospora species were not provided. Phaeoseptoriella only included four species, however, Ph. emmelinepankhurstiae, Ph. edithcowaniae, and Ph. eidagoldsteiniae have not been provided with morphological analyses (, ). Phaeoseptoriellapoaceicola differs from Ph. zeae in comparatively smaller conidiomata (90–100 μm diam. vs. 200–250 μm diam.), conidiogenous cells (hyaline, globose to subglobose vs. pale brown, ampulliform to doliiform), bigger conidia (30–41 μm long, 4–7 μm wide, cylindrical to subcylindrical, 7-septate vs. 14–23 μm long, 3–4 μm wide, fusoid-ellipsoid, 3-septate) (). Based on the guidelines for a polyphasic approach recommended for species boundary delimitation (; ), we introduce Phaeoseptoriella poaceicola as a novel taxon.

Figure 1 – Asexual morph of Phaeoseptoriella poaceicola (HKAS 128741, holotype) on a dead stalk of Dactylis glomerata a, b. Conidiomata on the host. c, d. Vertical section of conidiomata. e. Conidioma wall. i. Conidiogenous cells arise from the wall and develop conidia. f–h, j. Conidia. k. Germinating conidia. l. Cultures on PDA from above. m. Cultures on PDA from the reverse. Scale bars: c = 30 μm, d, e = 20 μm, f–h = 10 μm, i = 5 μm, j = 10 μm, k = 20 μm.