Cercospora musigena Nguanhom, 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 : 43

Cercospora musigena Nguanhom, Crous & U. Braun , sp. nov. ( Fig. 5 ). MycoBank MB812921

Type:— THAILAND. Chiang Mai: on leaves of Musa sp. ( Musaceae ), 27 May 2013, S. Seekanha (holotype CBS H-22292, culture ex-type CPC 24809 = CBS 140167, CPC 24831).

Leaf spots irregular, pale brown along the leaf margins, often surrounded by a yellow halo. Caespituli amphigenous, punctiform, brown. Stromata intraepidermal to subepidermal, brown, 30−45 μm diam. Conidiophores in moderately large fascicles (11−20 per fascicle), erumpent through the cuticle, brown, paler toward the apex, 3−5-septate, cylindrical, 1−3 times geniculate in upper part, tapering to flat-tipped loci, branched, 30−75 × 4−5 μm. Conidiogenous cells proliferating sympodially 1−4 times, integrated, terminal, rarely intercalary; conidiogenous loci distinct, apical or formed on shoulders due to sympodial proliferation, thickened and darkened, protruding, 2−3 μm diam. Conidia solitary, hyaline, straight to mildly curved, acicular, truncate at the base, obtuse at the apex, thin-walled, smooth, 15−130 × 3−5 μm, 2−20-septate, hila thickened, darkened, 2–2.5 μm diam.

Culture characteristics: —Colonies spreading, flat, with sparse to dense aerial mycelium, even margin, reaching 48 mm diam after 2 wk. On MEA surface pale purplish grey, with rosy buff outer region; reverse sepia. On PDA surface vinaceous-buff, with red diffuse pigment surrounding culture; reverse bay. On OA surface whitish, with patches of grey; reverse chestnut, with rust in outer region.

Etymology: —Named after the host from which it was isolated, Musa sp.

Notes: — Cercospora musigena is similar to C. hayi Calp. by its acicular conidia with truncate bases, being part of the C. apii complex ( Braun et al. 2014). In C. hayi , however, there are fewer conidiogenous loci per conidiogenous cell, and the conidial tips are acute to subacute ( Calpouzos 1955). C. apii s. lat. (including C. hayi ) on Musa spp. is genetically heterogeneous. Sequences retrieved from C. apii -like cultures isolated from banana clustered in three different clades ( Groenewald et al. 2013). However, the identity of the name C. hayi is still unresolved and will need to be clarified by means of epitypification ( Braun et al. 2014).

Figures

FIGURE 5. Cercospora musigena (CBS H-22292). A. Leaf spot; B, C. Conidiophores and conidiogenous cells; D−H. Conidia.—Scale bars: B−C = 50 μm; D−H = 30 μm.