Dothideomycetes » Dothideomycetes, genera incertae sedis » Chionomyces

Chionomyces meliolicola

Chionomyces meliolicola (Cif.) Deighton & Piroz., Mycol. Pap. 128: 75 (1972)                               Fig. 1, 2

Monacrosporium meliolicola Cif., Annls mycol. 36(2/3): 244 (1938)

Index Fungorum number: IF 311046; Facesoffungi number: FoF 06228

Parasitic on the surface of living leaves. Sexual morph: Undetermined. Asexual morph: Colonies effuse, white, floccose. Mycelium hyperparasitic, consists of dark-brown to black undulate, branched septate, thin and smooth-walled hyphae 3–4 µm wide, with thickly overgrowing superficial mycelium of leaf-inhabiting ascomycetes and bearing conidiophores as lateral branches. Conidiophores variable in length, up to 300 µm long, distributed singly or grouped onto loose fascicles, more or less erect, simple, colorless to pale brown, straight or flexuous with dense, refractive walls mainly towards the base, closely and markedly septate throughout or with the septa concentrated in the upper half, of variable in length. Conidiogenous cells holoblastic, percurrent, sympodial. Conidia 11–17 µm × 3–5 µm (x̅ = 15.1 × 4.7 µm, n = 10) produced successively and holoblastically, one at a time from the tips of the conidiophores which proliferate percurrently by flipping the entire conidial scar to one side and growing through the opening to leave behind a series of pseudo-annellations. The conidia are firstly ovoid then elongate to produce a papillate apex. Mature conidia are spindle-shaped, colourless to brown, thin and smooth-walled, 3–5-septate, with a wide truncate base and apical cell narrowing abruptly into beak-like curved projections and wide at the apex.

Notes – The herbarium material from PDD revealed very broad conidiophore tips (about 4 µm), broad conidial bases and apical cells extending into a long tail. The mostly 4-septate conidia measured 11–17 µm × 3–5 µm. The original author had given conidial measurements as 8–10 µm.

Material examined – NEW ZEALAND, Kauaeranga Valley, on unidentified leaves, 20 January 1974, J.M. Dingley (PDD 37163).

Economic significance Species of the genus Chionomyces were identified as hyper-parasitizing a Meliolales (one of the plant parasitic “black mildews") on an unidentified palm (Bronson 2018).