Petrakia echinata (Peglion) Syd. & P. Syd., Annls mycol. 11(5): 406 (1913)
Index Fungorum number: IF 192652; Facesofungi number: FoF 01821
≡ Epicoccum echinatum Peglion, Malpighia 8: 459 (1895).
Parasitic on living leaves of Acer pseudoplatanus L., forming numerous, conspicuous rounded, black, sporodochia. Sexual morph: Mycodidymella (Butin et al. 2013). Asexual morph: Sporodochia 90–110 μm high, 100–150 μm diam., dark brown to black, solitary, scattered to gregarious, occasionally confluent, superficial, erumpent, elliptical or irregular in outline, with a basal stroma variably developed, 20–30 μm thick, composed of cells of textura angularis to textura globulosa. Conidiophores reduced to conidiogenous cell arising from the uppermost cells of the basal stroma. Conidiogenous cells 12–35 × 3–10 μm, hyaline to pale yellow, integrated, annellidic, with 2–3 annellations, cylindrical, thick-walled, smooth. Conidia 22–45 × 12–32 μm (x̄ = 32 × 25 μm, n = 30), rounded to oval or broadly ellipsoidal,
muriform, with multi-transverse and longitudinal septa or oblique septa in the central zone, constricted at septa, thick-walled, smooth, at first hyaline, later becoming brown or dark brown, bearing 8–33 × 3–9 μm, cellular, long appendages; appendages, arising as a tubular extension of the body of the conidium, unbranched, narrow and attenuated, subhyaline, cylindrical, smooth-walled.
Culture characteristics: Colonies on PDA slow-growing, reaching 15 mm diam. after one week, circular, white to pale grey, velvety, felty, sparse, aerial, surface smooth with crenate edge, filamentous; reverse black at the central zone, white at the margin.
Material examined: ITALY, Province of Forlì-Cesena [FC], Camposonaldo, Santa Sofia, on living leaves of Acer pseudoplatanus L. (Sapindaceae), 20 February 2013, Erio Camporesi IT-1570 (MFLU 15–7568, reference specimen designated here), living culture MFLUCC 15–0582.
Notes: In the phylogenetic analysis, strain MFLUCC 15–0582 is closely related to Petrakia echinata (Li et al. 2016). The comparisons of ITS sequence data from both strains show 100 % similarity. Morphologically, strain MFLUCC 15–0582 has similar sporodochia and conidia characteristics to those of P. echinata, and the only distinguishing character is the dimension of the conidia. Strain MFLUCC 15–0582 has slightly larger conidia (22–45 × 12–32 μm, versus 16– 28 × 18–22 μm) than P. echinata. However, the differences noted here similarly reflect reasonable intraspecific variation. Petrakia echinata has been reported as a pathogen in Austria, Caucasus, Germany Switzerland and the Czech Republic (Kirisits 2007, Butin et al. 2013), and this is the first record of the species in Italy.