Monochaetia shaanxiensis N. Jiang, in Jiang, Voglmayr, Xue, Piao & Lia, Microbiology Spectrum: 10.1128/spectrum.00042-23, 10 (2023)
Index Fungorum number:IF 841307; MycoBank number: MB 841307; Facesoffungi number: FoF 11688
Etymology – named after the collection site of the type specimen, Shaanxi Province.
Diagnosis – morphologically distinct from the phylogenetically related species of M. kansensis by shorter basal appendage.
Pathogenic to host leaves. Asexual state: Conidiomata in culture sporodochial, aggregated or solitary, erumpent, pulvinate, dark brown, 150–450 μm diam., exuding dark brown conidial masses. Conidiophores septate and branched, hyaline, thin-walled. Conidiogenous cells hyaline, smooth, cylindrical to subcylindrical, annelidic, 11.5–20.5 × 2–3 μm, mean ± SD = 15.7 ± 2.7 × 2.4 ± 0.2 μm. Conidia fusoid, straight or slightly curved, 4-septate, smooth, slightly constricted at the septa, (19–)19.5–21.5(–22) × 6.5–7.5(–8.5) μm, mean ± SD = 20.6 ± 0.9 × 7.1 ± 0.5 μm (n = 50), L/W = 2.5–3.2; basal cell obconic with a truncate base, thin-walled, hyaline or pale brown, 3–4(–4.5) μm; median cells 3, trapezoid or subcylindrical, brown, thick-walled, the first median cell from base 4.5–5(–5.5) μm long, the second cell 3.5–4.5 μm long, the third cell (3–)3.5–4.5 μm long, together 11.5–13 μm long; apical cell conic with an acute apex, thin-walled, hyaline, (4–)4.5–5.5 μm long; basal appendage single, unbranched, tubular, centric, straight, 2–3 μm long, mean ± SD = 2.5 ± 0.3 μm; apical appendage single, unbranched, tubular, centric, straight, (3.5–)4–6.5(–8) μm long, mean ± SD = 5.1 ± 1.4 μm. Sexual morph: unknown.
Culture characteristics – Colonies on MEA flat, spreading, with radially folded surface and entire edge, luteous to olivaceous gray, reaching 35 mm in diameter after 10 days at 25°C, forming black conidiomata with black conidial masses; colonies on PDA flat, spreading, with flocculent aerial mycelium and undulate edge, white to pale luteous, reaching 45 mm in diameter after 10 days at 25°C, forming black conidiomata with black conidial masses.
Material examined – China, Shaanxi Province, Xian City, Zhouzhi County, Heihe Forest Park, on diseased leaves of Quercus baronii (Fagaceae), 6 September 2019, Yong Li (holotype CAF 800020 = JNH0016; ex-holotype culture CFCC 54419).
Distribution: China
Sequence data: ITS: OK339755 (ITS1/ITS4); LSU: OK339784 (LROR/LR5); tef1: OK358483 (EF1-728F/EF2); tub2: OK358492 (Bt2a/Bt2b)
Notes: Monochaetia shaanxiensis is phylogenetically close to M. hanzhongensis, M. kansensis, and M. lithocarpi (Fig. 1). However, M. shaanxiensis has a distinctly shorter apical appendage than M. lithocarpi (3.5 to 8 μm versus 13 to 23.5 μm in M. lithocarpi), a shorter basal appendage than M. kansensis (2 to 3 μm versus 3 to 15 μm in M. kansensis), and wider conidia than M. hanzhongensis (6.5 to 8.5 μm versus 5 to 6.5 μm in M. hanzhongensis).
Fig. 5. Morphology of Monochaetia shaanxiensis (CFCC 54419). A. Colony on PDA after 10 d at 25 °C; B. Colony on MEA after 10 d at 25 °C; C. Conidioma formed on PDA; D, E. conidiogenous cells giving rise to conidia; F, G. conidia. — Scale bars: C = 300 μm; D–G = 10 μm.