Harknessia Cooke, Grevillea 9 (no.51): 85 (1881)
MycoBank number: MB 8449; Index Fungorum number: IF 8449; Facesoffungi number: FoF 01683; 68 morphological species (Species Fungorum 2020), 38 species with sequence data.
Type species – Harknessia eucalypti Cooke
Notes – Harknessia species have been recorded in wide variety of habitats and normally they appear as leaf spots, wherein leaves with tip-dieback or leaf scorch and stem cankers occur (Crous et al. 1989, Wijayawardene et al. 2016b). Some species have been recorded from leaf and twig litter (Marincowitz et al. 2008). However, the pathogenicity of Harknessia species on host plants is not proven yet, since nobody has resolved it experimentally. Harknessia species with hyaline conidia and apical appendages were transferred to Mastigosporella by Höhnel (1917c), and species with brown conidia with apical and basal appendages were placed to Apoharknessia (Lee et al. 2004), whereas species with very thick conidial walls and longitudinal slits were included in Dwiroopa (Farr & Rossman 2003). Harknessia has enough molecular support to accommodate in a distinct lineage in Harknessiaceae. Currently, there are 74 Harknessia epithets in Index Fungorum (2020).
Yuan & Mohammed (1997) introduced Wuestneia epispora which was identical to the asexual morph of Harkenessia eucalypti. According to the cultural characters conidia of W. epispora are shorter (11–22 × 11–15 µm) than those of H. eucalypti (Crous et al. 1993). However, the average of conidial size (25.4 × 13.9 µm) by Yuan & Mohammed (1997) is closely similar with the averages of H. eucalypti (23 × 14 µm) (Nag Raj 1993). Therefore, Lee et al. (2004) treated this culture as authentic to H.eucalypti.
Figure 117 – Harknessia eucalypti (Material examined – USA, California, on leaves of Eucalyptus globulus. (Myrtaceae), Harknessia 1280, isotype K (M) 195744). a Herbarium specimen. b Conidiomata on host substrate. c Cross section of conidioma. d Peridium. e, f Conidia attached to conidiophores. g-k conidia are attached to conidiogenous cells. l Conidium with basal appendage. Scale bars: c = 100 μm, d-f = 20 μm, g-l = 10 μm.