Harknessia Cooke, in Cooke & Harkness, Grevillea 9(no. 51): 85 (1881)
Diaporthomycetidae, Diaporthales, Harknessiaceae, Harknessia
Saprobic or pathogenic, typically on leaf tissues. Sexual morph: Ascomata immersed, brown, perithecial, solitary or aggregated. Neck emergent to depressed. Ascomatal wall of 3–5 layers of brown cells of textura angularis. Paraphyses hyaline, septate, discrete between asci. Asci 8-spored, unitunicate, cylindrical to clavate, short pedicellate, with J- apical ring. Ascospores hyaline, uni- to biseriate, ellipsoid to fusoid, aseptate, thick-walled, guttulate, smooth-walled. Asexual morph: Coelomycetous, appearing as almost circular, black distinct spots. Conidiomata brown, erumpent, scattered, pycnidial, unilocular, globose to subglobose. Peridium containing 3–4 layers of brown-walled cells of textura angularis. Conidiophores hyaline, short, cylindrical, nearly globose, branched, mixed with peridium cells. Conidiogenesis cells hyaline to brown, holoblastic, bottle-shaped, cylindrical. Conidia hyaline when immature, brown at maturity, globose to ovoid, with a truncate apiculate apex and an obtuse to blunt base, smooth-walled, with longitudinal striations along the length of some conidia. Basal appendages hyaline, smooth, thin-walled, tubular, often collapsing (adapted from Maharachchikumbura et al. 2016).
Type species: Harknessia eucalypti Cooke, Grevillea 9(no. 51): 85 (1881)
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. 2016). 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 (1917), 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 it as 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.
Species illustrated in this entry:
Harknessia eucalypti Cooke
Crous PW, Knox-Davies PS, Wingfield MJ. 1989 – Newly-recorded foliage fungi of Eucalyptus spp. in South Africa. Phytophylactica 21, 85–88
Crous PW, Wingfield MJ, Nag Raj TR. 1993 – Harknessia species occurring in South Africa. Mycologia 85, 275– 280
Farr DF, Rossman AY. 2003 – Dwiroopa, a coelomycetous genus with two species. Mycoscience 44, 443–446
Höhnel F von. 1917 – Mykologische Fragmente. Nrn. 120–190. Annales Mycologici 15, 293–383
Lee S, Groenewald JZ, Crous PW. 2004 – Phylogenetic reassessment of the coelomycete genus Harknessia and its teleomorph Wuestneia (Diaporthales), and the introduction of Apoharknessia gen. nov. Studies in Mycology 50, 235–252
Maharachchikumbura SSN, Hyde KD, Jones EBG, McKenzie EHC et al. 2016 – Families of Sordariomycetes. Fungal Diversity 79, 1–317
Marincowitz S, Crous PW, Groenewald JZ, Wingfield MJ. 2008 – Microfungi occurring on the Proteaceae in the fynbos. CBS Biodiversity series 1–166
Nag Raj TR. 1993 – Coelomycetous anamorphs with appendage bearing conidia. Mycologue publications, Waterloo 1–1101
Wijayawardene NN, Hyde KD, Wanasinghe DN, Papizadeh M et al. 2016 – Taxonomy and phylogeny of dematiaceous coelomycetes. Fungal Diversity 77, 1–316
Yuan ZQ, Mohammed C. 1997 – Wuestneia epispora sp. nov. on stems of eucalypts from Australia. Mycological Research 101, 195–200