Petrakia echinata
Petrakia echinata (Peglion) Syd. & P. Syd. (1913).
≡ Epicoccum echinatum Peglion, Malpighia 8: 459 (1895).
Index Fungorum number: IF 192652; Facesoffungi number: FoF 01821, Fig. 1, 2
Description:
Parasitic on living leaves. Sexual morph: Unknown. Asexual morph: Conidiomata 105–110 μm diam., 105–115 μm high, sporodochial, superficial, scattered or in groups, dark brown to black. Conidiophores reduced to conidiogenous cells. Conidiogenous cells holoblastic, hyaline, smooth. Macroconidia and mycopappus-like propagules scattered or in groups, on dark brown, somewhat circular necroses on the upper surface of living leaves. Mycopappus-like propagules shortly stalked, sub-globose to ellipsoid, multicellular, parenchymatous, comprising somewhat isodiametric, globose cells, hyaline to pale brown, with up to 6 filamentous, hyaline hyphal appendages. Macroconidia 20−30 × 18−25 µm (x̄ = 22 × 21.1 µm, n = 10), formed on epiphyllous sporodochia, embedded in the leaf tissues with a cone shaped stroma, mature sporodochia blackish brown. Macroconidia formed on epiphyllous sporodochia, embedded in the leaf tissues in circular shaped stroma, mature sporodochia blackish brown. Macroconidia dark brown, muriform, ellipsoid to elongated spindle-shaped, cells angular, somewhat cubic, cell walls dark-brown, smooth. Macroconidia bearing one apical and 0–4 (6) side projections, projections straight with conical to spherical tips, hyaline to light brown, mostly without septa; pedicels up to 11–30 µm long and 3.5–7.8 µm wide.
Material examined: France, from leaf of Acer pseudoplatanus (Sapindaceae), Van der Aa H.A. (BR5020172196214).
Fig. 1 Petrakia echinata (BR5020172196214). a–d Herbarium material and appearance of sporodochia on the host surface. e, f Squash mount of sporodochia. g Conidiogenesis. h–p Conidia (i: immature conidia attached to the conidiophore). Scale bars: d = 200 μm, e, f = 50 μm, g = 30 μm, h, j = 20 μm, i, k–p = 10 μm.
Fig. 2 Mycodidymella teleomorph of Petrakia echinata (re-drawn from Fig. 1 in Butin and Holdenrieder 2013). a Pseudothecia. b Section through a pseudothecium. c Asci and paraphyses. d Ascospores. Scale bars: a = 1 mm, b = 100 μm, c, d = 10 μm.
Importance and distribution
There are 13 Petrakia epithets in Index Fungorum (2022), but several species have been transferred to Ernakulamia, Pseudopetrakia and Xenostigmina. Petrakia comprises ten species known on leaves of Aesculus turbinata (Sapindaceae), leaves of Acer sp. (Sapindaceae), leaves of Fagus crenata (Fagaceae), Juniperus (Cupressaceae), living leaves of Fagus japonica (Fagaceae) and decaying culms of Miscanthus floridulus (Poaceae). Petrakia is known from Asia (Hong Kong, Japan), Caucasus and Europe (Germany, Italy, Netherlands).
References
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