Classification: Sordariomycetes, Diaporthomycetidae, Diaporthales, Apoharknessiaceae.
Type species: Apoharknessia insueta (B. Sutton) Crous & S.J. Lee, basionym: Harknessia insueta B. Sutton. Holotype of H. insueta: IMI 22697. Epitype and ex-epitype strain designated by Lee et al. (2004): CBS H-9913, CBS 111377 = STE-U 1451.
DNA barcodes (genus): ITS, LSU.
DNA barcodes (species): ITS, cal, tub2. Table 2.
|Species||Isolates1||GenBank accession numbers2||References|
|Apoharknessia eucalypti||CBS 142518T||MG934432||MG934510||MG934505||Present study|
|Ap. eucalyptorum||CBS 142519T||KY979752||KY979867||KY979919||Crous et al. (2017a)|
|Ap. insueta||CBS 111377ET||JQ706083||MG934511||MG934506||Crous et al. (2012c), present study|
CBS: Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands. T and ET indicate ex-type and ex-epitype strains.
ITS: internal transcribed spacers and intervening 5.8S nrDNA; cal: partial calmodulin gene; tub2: partial β-tubulin gene.
Conidiomata pycnidial, separate to gregarious, subepidermal, becoming erumpent, stromatic, amphigenous, depressed globose or subglobose to irregular, unilocular, glabrous; opening irregularly, with yellowish, furfuraceous cells, lacking a definite ostiole; conidiomatal wall of textura angularis. Conidiophores reduced to conidiogenous cells lining cavity. Conidiogenous cells lageniform to ampulliform or ampulliform to subcylindrical, hyaline, smooth, in mucilage, percurrently proliferating once or twice near apex. Conidia broadly ellipsoidal to obovoid or obliquely gibbose, apex obtusely rounded, aseptate, non-apiculate, medium brown or brown, with or without a longitudinal hyaline band on flat surface, thick-walled, smooth, with or without striations along length of conidia, with prominent central guttule; basal appendage absent or hyaline, tubular, smooth, thin-walled, devoid of cytoplasm; apical appendage absent or hyaline, conical or tubular, short, smooth, thin-walled, devoid of cytoplasm. Sexual morph unknown.
Culture characteristics: Colonies flat on MEA, PDA and OA, with sparse or moderate aerial mycelium, smooth, lobate margins, fast sporulating. On MEA surface greenish black or olivaceous black in centre, dirty white in outer region; reverse olivaceous grey in centre, dirty white in outer region.
Optimal media and cultivation conditions: MEA, PDA and OA under continuous near-ultraviolet light at 25 °C to promote sporulation.
Distribution: Brazil, Colombia, Cuba, Malaysia and Mauritius.
Disease symptoms: Leaf spots.
Notes: The genus Apoharknessia was established by Lee et al. (2004) for Ap. insueta, a presumed foliar pathogen of eucalypts in Brazil, Colombia, Cuba and Mauritius. The genus included two species following the description of Ap. eucalyptorum to accommodate a presumed endophyte of Eucalyptus pellita isolated from collections made in Malaysia (Crous et al. 2017a).
Apoharknessia is distinguished from Harknessia by having an apical appendage on its conidia, and cultures that lack fluffy aerial mycelium and sporulate abundantly on the aerial hyphae. Cultures of Harknessia s. str. are slow to sporulate, and tend to form abundant pycnidial conidiomata in culture (Lee et al. 2004).
Recently, the family Apoharknessiaceae was introduced based on a phylogenetic study of the members of the Diaporthales, in order to accommodate Apoharknessia, designated as the type genus of the family, together with Lasmenia, which is also a genus associated with plant disease (Senanayake et al. 2017).
Crous & M.J. Wingf., sp. nov. MycoBank MB820945. Fig. 3.
Etymology: Name refers to Eucalyptus, the host genus from which this fungus was collected.
Foliicolous, isolated from leaves incubated in moist chambers (presumed endophytic). Conidiomata up to 250 μm diam, pycnidial, solitary to gregarious, subepidermal, becoming erumpent, stromatic, amphigenous, depressed globose; opening irregularly, with yellowish, furfuraceous cells; conidiomatal wall of textura angularis. Conidiophores reduced to conidiogenous cells lining cavity. Conidiogenous cells 8–12 × 3–5 μm, ampulliform to subcylindrical, hyaline, smooth, in mucilage, percurrently proliferating once or twice near apex. Conidia (7–)8–10(–11) × (5–)6(–7) μm, broadly ellipsoid to obovoid, apex obtusely rounded, aseptate, non-apiculate, medium brown, thick-walled, smooth, striations along length of conidium body, with prominent central guttule. Basal appendage absent or 0–2 μm long, 2 μm diam, hyaline, tubular, smooth, thin-walled, devoid of cytoplasm.
Culture characteristics: Colonies on MEA, PDA and OA, with moderate aerial mycelium and smooth, lobate margins, reaching 60 mm diam after 2 wk at 25 °C. On MEA surface greenish black in middle, dirty white in outer region; reverse olivaceous grey in centre, dirty white in outer region. On PDA surface and reverse olivaceous grey in centre, dirty white in outer region. On OA surface greenish black in middle, outer region dirty white.
Material examined: Malaysia, Sabah, isolated from leaves of Eucalyptus pellita (Myrtaceae), May 2015, M.J. Wingfield (holotype CBS H-23081, culture ex-type CPC 27550 = CBS 142518).
Notes: Apoharknessia eucalypti is an odd member of the genus in that its conidia generally lack an apical appendage. The latter was observed on one or two conidia, irrespective of the media used for cultivation. The ITS sequence of Ap. eucalypti is only 92 % similar to that of Ap. insueta [GenBank JQ706083; Identities = 569/618 (92 %), 33 gaps (5 %)] and 97 % similar to that of Ap. eucalyptorum [GenBank KY979752; Identities = 604/621 (97 %), 5 gaps (0 %)].
Authors: P.W. Crous, Y. Marin-Felix, J.Z. Groenewald & M.J. Wingfield