Monochaetia hanzhongensis N. Jiang, in Jiang, Voglmayr, Xue, Piao & Lia, Microbiology Spectrum: 10.1128/spectrum.00042-23, 2 (2023)
Index Fungorum number:IF 841304; MycoBank number: MB 841304; Facesoffungi number: FoF 11684
Etymology – named after the collection site of the type specimen, Hanzhong City.
Diagnosis – distinct from the phylogenetically related species of M. lithocarpi by host association.
Pathogenic to host leaves. Asexual state: Conidiomata in culture sporodochial, aggregated or solitary, erumpent, pulvinate, black, 300–850 μm diam., exuding black conidial masses. Conidiophores indistinct, usually reduced to conidiogenous cells. Conidiogenous cells hyaline, smooth, cylindrical to subcylindrical, annelidic, 5–13 × 3–4 μm, mean ± SD = 10 ± 3 × 3.7 ± 0.3 μm. Conidia fusoid, straight or slightly curved, 4-septate, smooth, slightly constricted at the septa, (17.5–)18–20(–21) × (5–)5.5–6(–6.5) μm, mean ± SD = 19 ± 1.2 × 5.7 ± 0.3 μm (n = 50), L/W = 2.9–3.8; basal cell obconic with a truncate base, thin-walled, hyaline or pale brown, 3–4.5(–5) μm; median cells 3, trapezoid or subcylindrical, brown, thick-walled, the first median cell from base (3.5–)4–5(–5.5) μm long, the second cell (3–)3.5–4 μm long, the third cell 3.5–4 μm long, together (10–)10.5–12.5(–13) μm long; apical cell conic with an acute apex, thin-walled, hyaline, 2.5–4 μm long; basal appendage single, unbranched, tubular, centric, straight or bent, (3–)3.5–9.5(–12) μm long, mean ± SD = 6.3 ± 3.4 μm; apical appendage single, unbranched, tubular, centric, straight or bent, (6.5–)7–18.5(–23) μm long, mean ± SD = 12.9 ± 5.7 μm. Sexual morph unknown.
Culture characteristics – colonies on malt extract agar (MEA) flat, spreading, with flocculent aerial mycelium, folded surface, and diffuse edge, white to fawn, reaching 50 mm in diameter after 10 days at 25°C, forming black conidiomata with black conidial masses; colonies on potato dextrose agar (PDA) flat, spreading, with flocculent aerial mycelium and undulate margin, white to pale luteous, reaching 40 mm in diameter after 10 days at 25°C, forming black conidiomata with black conidial masses.
Material examined – China, Shaanxi Province, Hanzhong City, Foping County, Dongshan Mountain, on diseased leaves of Quercus variabilis (Fagaceae), 7 September 2019, Yong Li (holotype CAF 800016 = JNH0012; ex-holotype culture CFCC 54451).
Distribution –China
Sequence data –ITS: OK339747 (ITS1/ITS4); LSU: OK339776 (LROR/LR5); tef1: OK358475 (EF1-728F/EF2); tub2: OK358484 (Bt2a/Bt2b)
Notes – Monochaetia hanzhongensis is phylogenetically close to Monochaetia dimorphospora, Monochaetia kansensis, M. lithocarpi, Monochaetia quercus, and M. shaanxiensis (Fig. 1). Morphologically, M. hanzhongensis is similar to M. lithocarpi in conidial size (17.5 to 21 by 5 to 6.5 μm versus 15 to 24.5 by 4.5 to 7 μm in M. lithocarpi) but can be distinguished from M. lithocarpi by sequence data (nucleotide differences in ITS: 10/524 nucleotides [1.91%] and a 32-bp insertion; tef1: 68/473 nucleotides [14.38%], 6-bp insertions, and 7-bp gaps; tub2: 39/421 nucleotides [9.26%] and 4-bp insertions). M. hanzhongensis differs from M. dimorphospora, M. kansensis, and M. shaanxiensis in conidial width (5 to 6.5 μm versus 4 to 4.5 μm in M. dimorphospora, 6 to 8 μm in M. kansensis, and 6.5 to 8.5 μm in M. shaanxiensis) and has shorter conidia than M. quercus (17.5 to 21 μm versus 22.5 to 29 μm in M. quercus).
Fig. 1. Morphology of Monochaetia hanzhongensis (CFCC 54451). 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–F. conidiogenous cells giving rise to conidia; G. conidia. — Scale bars: C = 500 μm; D–G = 10 μm.