Foliicolous, occurring on needles of Picea engelmanni. Sexual morph: undetermined. Asexual morph: Conidiomata 200–300 µm diam., 150–200 µm high, dark brown to black, amphigenous, pycnidial, solitary to gregarious or confluent, hypophyllous, deeply immersed, later opening a circular pore in the middle part of overlapping host tissue, but conidia released via lateral ostiole, depressed globose in sectional view, unilocular, glabrous. Ostiole single, subcylindrical, laterally located. Conidiomatal wall 10–100 µm wide, composed of thick-walled, pale brown to hyaline cells of textura angularis in the basal and lateral part, passing into relatively thick-walled, pale brown to brown cell of textura intricata to textura epidermoidea in the upper part, becoming dark brown cells of textura angularis in the ostiolar region. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 5–15 × 3–7 µm, hyaline, enterolastic, phialidic, lageniform to conical, determined, smooth-walled. Conidia 21–35 × 5.7–8.6 µm ( = 27 × 7.3 µm; n = 30), hyaline, subcylindrical, with rounded apex, and narrow, truncate base bearing marginal frills, straight, unicellular, smooth-walled, bearing a funnel-shape or irregular, mucoid, apical appendage.
Material examined: Canada, Alberta, 31 mile N. W. of Rocky Mountain Ranger Station, on needles of Picea engelmanni Engelm. (Pinaceae), 7 July 1966, J. Petty & F. March (DAOM 145420).
Notes: Collection DAOM 145420 was deposited as Darkera parca by Whitney et al. (1975), but it has smaller conidia than DAOM 145413b (holotype, 37–54 × 8.3–13.8 µm ( = 42 × 10.7 µm). In addition, collection DAOM 145420 has phialidic conidiogenous cells whereas they are distinctly annellidic in DAOM 145413b. These two collection are probably not conspecific, but lacking molecular data, this hypothesis cannot be confirmed.
Darkera sp. (DAOM 145420) a, b Herbarium package and specimen. c, d Appearance of brown to dark brown conidiomata on the host. e–f Vertical section of conidiomata. g Section of peridium. h Ostiole. i–o Conidiogenous cells and developing conidia (arrows show apical mucoid appendages). p–s Conidia. Scale bars c = 500 µm, d = 200 µm, e–f = 100 µm, g–h = 50 µm, i–s = 10 µm.
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