Cercospora cyperacearum 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 : 40-41

Cercospora cyperacearum Cheew., Crous & U. Braun , sp. nov. ( Fig. 3 ). MycoBank MB812919

Type: — THAILAND. Chiang Mai: on leaves of Cyperus alternifolius ( Cyperaceae ), 12 May 2013, S. Seekanha (holotype CBS H-22290, culture ex-type CPC 23918 = CBS 140165).

Other specimens examined: — THAILAND. Chiang Mai: on unknown monocot, 12 May 2013, S. Seekanha, CPC 24811; Lamphun on leaves of Solanum mammosum ( Solanaceae ), 9 Dec. 2010, J. Nguanhom, CPC 22014.

Leaf spots amphigenous, pale brown to brown, margin indefinite, elongated to irregular. Caespituli amphigenous, punctiform, brown. Stromata substomatal to intraepidermal, brown, 38–63 μm high, 18–38 μm wide. Conidiophores fasciculate, pale olivaceous, paler and narrower towards the apex, unbranched, main portion straight, subcylindrical, only conidiogenous cells distinctly geniculate, 18−68 × 4−5 μm. Conidiogenous cells proliferating sympodially 5−9 times, integrated, terminal, 18–35 μm long, conidiogenous loci conspicuous, thickened and darkened, apical and lateral, circumspersed, 1−3 μm diam. Conidia solitary, hyaline, thin-walled, smooth, obclavate-cylindrical, subacute to acute at the apex, truncate at the base, 40−63 × 2−2.5 μm, indistinctly 1–6-septate, hila slightly thickened, darkened and refractive, 1−3 μm diam.

Culture characteristics: —Colonies spreading, with dense aerial mycelium, reaching 40 mm diam after 2 wk. On MEA surface green-glaucous with pink pigment surrounding colony with undulate margins; reverse fucous-black. On PDA surface smoke grey with pink at the margin, entire margin; reverse fucous-black. On OA surface dense mycelium, with sparse entire margin, pure olivaceous-grey with diffuse livid red pigment surrounding colony; reverse dark vinaceous with lavender grey at the centre.

Etymology: —Epithet derived from the host genus, Cyperus .

Notes: — Cercospora cyperacearum is undoubtedly plurivorous, as it is known from DNA sequences retrieved from unrelated hosts, including dicots and monocots, rendering a final conclusion impossible. The occurrence on additional hosts cannot be excluded and is probable, i.e., previously described Cercospora species might be involved. The Cercospora species described from Cyperus spp. are morphologically distinct ( Braun et al. 2014). Cercospora cyperigena U. Braun & Crous has much shorter, 0–1-septate conidiophores, 5–20 × 2–5 μm, and C. cyperi Sawada has small stromata, 10–25 μm diam, smaller conidiogenous loci, (1–)1.5–2(–2.5) μm diam, and broader conidia, (2–)2.5– 5(–5.5) μm ( Braun et al. 2014). Cercospora cyperacearum on Cyperus alternifolius in Thailand is characterised by forming large stromata and narrow conidia, and agrees well with the description of Cercospora ugandensis in Vasudeva (1963) based on Indian material on Cyperus sp. , which is, however, not in agreement with the original description of this species that has been reduced to synonymy with C. cyperi in Braun et al. (2014). The characters of conidiophores and conidia of Cercospora spp. on Solanum are not in agreement with the material on Solanum mammosum . C. solanicola and C. melongenae are C. apii -like, i.e., with consistently acicular conidia, and were reduced to synonymy with C. physalidis s. lat. in Braun & Mel’nik (1997), which was considered to be part of the C. apii s. lat. complex in Crous & Braun (2003). These species are characterised by having long, pluriseptate conidiophores to 200 μm, and conidia to 300 × 2.5–5 μm. The conidiophores in C. solani agree well with those of C. cyperacearum but the lesions are indistinct and the acicular conidia are 3.5–6 μm wide ( Chupp 1954; type material examined: Thüm., Mycoth. univ. 2070, HAL). C. solanigena ( Bhartiya et al. 2000) , described from India on Solanum melongena , resembles C. cyperacearum . However, the stromata are smaller, 10–30 μm diam, and the conidiophores are 16–100 × 3–5 μm, 1–6-septate, with conidia being cylindrical-obclavate to acicular (based on the original illustrations), 15–85 × 2–5 μm, 1–5-septate.

Figures

FIGURE 3. Cercospora cyperacearum (CBS H-22290). A. Leaf spot; B. Close-up of leaf spot; C, D. Conidiophores and conidiogenous cells; E−G. Conidia; H. Colony on MEA.—Scale bars: C−G = 40 μm.