Neocoleroa metrosideri P.R. Johnst., 2016

Johnston, Peter R. & Park, Duckchul, 2016, Neocoleroa metrosideri sp. nov. (Sympoventuriaceae, Venturiales), Phytotaxa 253 (3), pp. 214-218 : 216-217

Neocoleroa metrosideri P.R. Johnst. , sp. nov. ( Fig. 2 )

MycoBank MB 815460

Diagnosis: Differs from Neocoleroa sibirica by its host substrate ( Metrosideros rather than Vaccinium ) and larger ascospores (18–21 (–24) × (6.5–) 7–8 μm rather than 12 × 2–2.5 μm).

Etymology: refers to host substrate.

Holotype: NEW ZEALAND. Auckland, Glen Innes, Auckland University Tamaki campus (36.883037 S 174.849881 E), on living leaves of Metrosideros excelsa , 6 October 2015, P. R. Johnston ( PDD 107531 , holotype; ex type culture ICMP 21139 ). GenBank accession numbers KU131678 , KU131677 .

Leaf spots 3–5 mm diam., round or irregular in shape, barely visible on the upper surface of host leaf, diffuse reddish area with a slightly darker edge; well differentiated on lower surface of host leaf, slightly raised, pale grey with a narrow reddish border. Pseudothecia solitary or in small groups on the lower surface. External hyphae sparse, branched, walls darkened, thin, tangled amongst hairs of the leaf tomentum. Fungal hyphae within the epidermal cells of the host, possibly penetrating directly through cuticle. Pseudothecia superficial amongst host leaf tomentum, globose, 0.1–0.15 mm diam., black-walled, sunken and disc-like when mature, small central ostiole; setae 15–25 × 4–5 μm, straight, branched dichotomously several times near the apex, tips of branches rounded, walls pale brown, slightly thickened. Pseudothecial wall 10 μm thick, comprising 2–3 rows of globose to short-cylindric cells with walls barely thickened, darker in outernmost rows of cells. Hamathecium with pseudoparaphyses joined both top and bottom, narrow-cylindric, 1.5–2 μm diam., branched and anastomosing, occasionally septate, persistent. Asci about 60 × 20 μm, subsaccate to broad-cylindric, foot-like base, broadest in lower half, tapering gradually to rounded apex, bitunicate, fissitunicate, 8-spored, forming near base of pseudothecia. Ascospores 18–21 (–24) × (6.5–) 7–8 μm (average 20.2 × 7.3 μm), 1–septate, constricted at septum, upper cell wider than the lower cell, tapering to rounded ends, hyaline. Growth in culture very slow, colonies 1.5–3 mm diam. after 4 weeks on standard agar such as PDA, MEA, and Oatmeal agar. Cultures dark grey-brown, mostly immersed in agar with cottony dark aerial mycelium. Mycelium dark walled, some cells slightly swollen. No conidia observed.

Figures

FIGURE 2. Neocoleroa metrosideri (PDD 107531). A, leaf spots, upper surface of leaf. B, leaf spots, lower surface of leaf. C, detail of pseudothecia on lower surface of leaf. D, crushed pseudothecium showing apically branched setae and released asci. E, pseudothecium in vertical section. F, detail of fungal tissue within host epidermal cells in vertical section. G, asci and pseudoparaphyses. H, ascospores. Scale bars, a–b = 5 mm; c = 100 μm; d = 50 μm; e–h = 20 μm.