Cercospora glycinicola Cheew., Crous & U. Braun, 2015

Nguanhom, Jeerapa, Cheewangkoon, Ratchadawan, Groenewald, Johannes Z., Braun, Uwe, To-Anun, Chaiwat & Crous, Pedro W., 2015, Taxonomy and phylogeny of Cercospora spp. from Northern Thailand, Phytotaxa 233 (1), pp. 27-48 : 39

Cercospora glycinicola Cheew., Crous & U. Braun , sp. nov. ( Fig. 2 ). MycoBank MB812918

Type: — THAILAND. Chiang Mai: on Glycine max ( Fabaceae ), 29 Mar. 2013, S. Seekanha (holotype CBS H-22289, culture ex-type CPC 23911 = CBS 140164, CPC 23912).

Leaf spots amphigenous, subcircular to irregular, pale brown, surrounded by a darker brown margin, 1−3 mm diam. Mycelium internal. Caespituli amphigenous, punctiform, brown. Stromata brown, intraepidermal or substomatal, 32.5−57.5 μm diam. Conidiophores in moderately dense fascicles (4−25), straight or sinuous to geniculate due to sympodial proliferation, unbranched, brown, paler toward the apex, 30−113 × 4−6 μm, 1−4-septate. Conidiogenous cells proliferating sympodially, integrated, terminal or conidiophores reduced to conidiogenous cells, 28−60 μm long; conidiogenous loci conspicuous, apical and formed on shoulders caused by geniculation, lateral, multi-local, loci distinctly thickened, darkened, 3–4 μm diam. Conidia solitary, obclavate-cylindrical, hyaline, obtuse at the apex, truncate to slightly obconically truncate at the base, 1−3-septate, 23−83 × 3−5 μm; hila thickened and darkened, 2.5–3 μm diam.

Culture characteristics: —Colonies spreading, with moderate to dense, felty aerial mycelium, entire to undulate margin, reaching 42 mm diam after 2 wk. On MEA white, with somewhat greyish pink exudates. On PDA white to slightly grey, with diffuse red pigment in agar surrounding colony. On OA white to slightly grey, with diffuse red pigment in agar.

Etymology: —Named after its Glycine -inhabiting habit.

Notes: — Cercospora glycinicola is morphologically close to C. sojina ( Shin & Kim 2001) but distinct in having shorter conidiophores (30–113 μm, versus 40–200 μm) and above all narrower conidia with few septa (3–5 μm wide, 1–3-septate, versus 4–8 μm wide, 3–7-septate). Phylogenetically it is also distinct from species presently known from DNA sequence data, including C. sojina . However, although these two isolates originate from the same lesion, they were morphologically different. Isolate CPC 23911 had more geniculate conidiophores, shorter conidiogenous cells (28−38 μm) and slightly shorter conidia (23−68 μm). In contrast, isolate CPC 23912 had straight conidiophores, longer conidiogenous cells (45−60 μm) and somewhat acicular conidia. However, phylogenetically the two isolates only differed via one nucleotide position in cmdA.

Figures

FIGURE 2. Cercospora glycinicola (CBS H-22289).A. Leaf spot; B. Close-up of leaf spot; C, D. Conidiophores and conidiogenous cells; E−I. Conidia; J. Colony on MEA.—Scale bars: C−D = 40 μm; E−I = 50 μm.