Synonym: Phomopsis, Sacc., Syll. fung. (Abellini) 2: 484. 1883.
Classification: Sordariomycetes, Sordariomycetidae, Diaporthales, Diaporthaceae.
Type species: Diaporthe eres Nitschke. Lectotype designated by Udayanga et al. (2014a): B 70 0009145. Epitype and ex-epitype strain designated by Udayanga et al. (2014a): BPI 892912, AR5193 = CBS 138594.
DNA barcodes (genus): ITS.
BRIP: Queensland Plant Pathology Herbarium, Brisbane, Australia; CBS: Westerdijk Fungal Biodiversity Institute, Utrecht, the Netherlands; CFCC: China Forestry Culture Collection Center, Beijing, China; CGMCC: Chinese General Microbiological Culture Collection Center, Beijing, China; DAOM: Plant Research Institute, Department of Agriculture (Mycology), Ottawa, Canada; DAOMC: Canadian Collection of Fungal Cultures, Ottawa, Canada; FAU: Isolates in culture collection of Systematic Mycology and Microbiology Laboratory; FFPRI: Forestry and Forest Products Research Institute, Japan; ICMP: International Collection of Micro-organisms from Plants, Landcare Research, Private Bag 92170, Auckland, New Zealand; IFRDCC: International Fungal Research and Development Culture Collection; MFLU: Mae Fah Luang University herbarium, Thailand; MFLUCC: Mae Fah Luang University Culture Collection, Chiang Rai, Thailand; LC: Working collection of Lei Cai, housed at Institute of Microbiology, Chinese Academy of Sciences, Beijing, China. T indicates ex-type strains.
ITS: internal transcribed spacers and intervening 5.8S nrDNA; tub2: partial β-tubulin gene; his3: partial histone H3 gene; tef1: partial elongation factor 1-alpha gene; cal: partial calmodulin gene.
Ascomata immersed in substrate, subglobose or irregular, solitary or clustered in groups, often erumpent through a pseudostroma mostly surrounding ascomata with more or less elongated ascomatal necks. Pseudostroma distinct, often delimited with dark lines. Asci unitunicate, 8-spored, sessile, elongate to clavate or cylindrical, loosening from ascogenous cells at an early stage and floating free in ascomata. Ascospores biseriate to uniseriate in ascus, fusoid, ellipsoid to cylindrical, straight, inequilateral or curved, septate, hyaline, sometimes with appendages. Conidiomata pycnidial, deeply embedded in culture on several media, globose to conical, eustromatic, multilocular, occasionally with ostiolate necks, scattered or aggregated, brown to black, surface covered with hyphae, cream to pale luteous or yellowish, conidial droplets or cirrus exuding from central ostioles; conidiomatal wall consisting of pale brown, thick walled, textura angularis. Conidiophores cylindrical to clavate, straight to sinuous, densely aggregated, branched, 0–6-septate, smooth, hyaline in upper region, pale brown at base. Conidiogenous cells phialidic, hyaline, cylindrical, terminal and lateral, tapering slightly towards apex. Paraphyses occasionally produced, intermingled among conidiophores, hyaline, smooth, 1–3-septate. Alpha conidia aseptate, generally hyaline, smooth, fusiform to ellipsoidal, with obtuse or acute to rounded ends, non- to multi-guttulate, but often bi-guttulate. Beta conidia aseptate, hyaline, filiform, smooth, straight or more often hooked, eguttulate, tapering or truncated towards ends. Gamma conidia rarely produced, hyaline, smooth, non- to multi-guttulate, fusiform to subcylindrical with acute or rounded apex (adapted from Gomes et al., 2013, Udayanga et al., 2014a).
Culture characteristics: Colonies on MEA, PDA and OA producing abundant compact, flattened, aerial mycelium, sometimes in rings, with an entire to irregular margin, white, cream to yellowish or pale olivaceous grey, smoke grey to grey, cottony; reverse pale brown to grey, dark green, producing brownish dots with age, with solitary or aggregated conidiomata at maturity.
Optimal media and cultivation conditions: On MEA, PDA and OA at 25 °C, or sterile pine needles placed on SNA at 25 °C under near-ultraviolet light (12 h light, 12 h dark) to induce sporulation of the asexual morph.
Hosts: On a wide range of plant families.
Notes: The genus Diaporthe presently includes 213 species supported by ex-type cultures and supplementary DNA barcodes, which include endophytes, saprobes and important plant pathogenic species. Recent phylogenetic analyses of the genus Diaporthe grouped some of those species into complexes, such as D. arecae, D. eres and D. sojae (Huang et al., 2013, Udayanga et al., 2014a, Udayanga et al., 2015). Several pathology studies confirmed Diaporthe species to be associated with diverse suites of diseases (Fig. 7) on a broad range of economically important agricultural crops (Udayanga et al. 2011). More than one Diaporthe species is frequently reported as causative agents of the same disease (Thompson et al., 2011, Guarnaccia et al., 2016).
Although Diaporthe was historically considered monophyletic based on the typical phomopsis-like asexual morph, the paraphyletic nature of this genus was recently revealed (Gao et al., 2017, Senanayake et al., 2017). Most of the known species in early literature were described in relation to their host association and morphological characters. However, a single species of Diaporthe can be found on diverse hosts, and can co-occur on the same host or lesion in different life modes. Phylogenetic studies demonstrated that morphological characters are not always reliable for species level identification due to their variability under changing environmental conditions (Gomes et al. 2013). As a consequence, identification and description of species based on host association alone is no longer tenable. For accurate species delimitation, phylogenetic inference of the ITS, cal, his3, tef1 and tub2 or combinations of these is required.
References: Mostert et al., 2001, Van Niekerk et al., 2005, Thompson et al., 2011, Guarnaccia et al., 2016, Guarnaccia et al., 2018 (morphology, pathogenicity and phylogeny); Udayanga et al., 2011, Udayanga et al., 2014a, Udayanga et al., 2015, Gomes et al., 2013 (morphology and phylogeny); Dissanayake et al., 2017b, Dissanayake et al., 2017c, Gao et al., 2017 (phylogeny).
Guarnaccia & Crous, sp. nov. MycoBank MB823830. Fig. 10.
Etymology: Name refers to Acacia heterophylla, the host from which this fungus was collected.
On PNA: Conidiomata 250–350 μm diam, pycnidial, globose or irregular, solitary, deeply embedded in media, erumpent, dark brown to black, whitish translucent to yellow conidial drops and/or cirrus exuded from ostioles; conidiomatal wall consisting of 3–4 layers of medium brown textura angularis. Conidiophores 7–22 × 1.5–4 μm, hyaline, smooth, 0–1-septate, densely aggregated, cylindrical, straight. Conidiogenous cells 6–9 × 1–2 μm, phialidic, hyaline, terminal, cylindrical, tapered towards apex. Paraphyses not observed. Alpha conidia 6–10.5 × 2.5–4.5 μm, mean ± SD = 8.4 ± 1.1 × 3.2 ± 0.4 μm, L/W ratio = 2.6, aseptate, ovate to ellipsoidal, hyaline, multi-guttulate and acute or rounded at both ends. Beta conidia 17–24 × 1–2 μm, mean ± SD = 21.7 ± 1.8 × 1.5 ± 0.3 μm, L/W ratio = 14.5, hyaline, aseptate, eguttulate, filiform, curved, tapering towards both ends. Gamma conidia not observed.
Culture characteristics: Colonies covering medium within 10 d at 21 °C, with surface mycelium flattened, dense and felty. Colony on MEA, PDA and OA at first white, becoming cream to yellowish, flat on MEA and OA, dense, felted on PDA; reverse grey with brownish dots with age, with visible solitary conidiomata at maturity on all media.
Material examined: France, La Rèunion, on Acacia heterophylla (Fabaceae), 8 Mar. 2015, P.W. Crous (holotype CBS H-23376, culture ex-type CBS 143769 = CPC 26215).
Notes: Diaporthe heterophyllae is phylogenetically close but clearly differentiated from D. eres based on ITS, tef1, tub2, his3 and cal sequence similarity (98 %, 88 %, 97 %, 95 %, and 97 %, respectively). Morphologically, D. heterophyllae differs from D. eres in its longer alpha conidia (6.5–10.5 vs. 6–8.5 μm) and in its shorter beta conidia (17–24 vs. 22–28 μm) (Udayanga et al. 2014a).
Etymology: Name refers to Euclea racemosa, the host from which this fungus was collected.
On PNA: Conidiomata 350–600 μm diam, pycnidial, globose or irregular, solitary, deeply embedded in media, erumpent, dark brown to black, yellowish translucent to pale brown conidial drops and/or cirrus exuded from ostioles; conidiomatal wall consisting of 3–4 layers of pale brown textura angularis. Conidiophores 7–17 × 2–4 μm, hyaline, smooth, 0–1-septate, densely aggregated, cylindrical, straight. Conidiogenous cells 5.5–8 × 1–2 μm, phialidic, hyaline, terminal, subcylindrical, tapered towards apex. Paraphyses not observed. Alpha conidia 4–6.5 × 2–3 μm, mean ± SD = 5.7 ± 0.6 × 2.3 ± 0.3 μm, L/W ratio = 2.5, aseptate, ellipsoidal to subcylindrical, hyaline, non- to multi-guttulate and acute or rounded at both ends. Beta and gamma conidia not observed.
Culture characteristics: Colonies covering medium within 10 d at 21 °C, with surface mycelium flattened, dense and felty. Colony on MEA and OA at first white, becoming olivaceous to dark grey. On PDA at first white, becoming white to yellowish; reverse grey with brownish dots with age, with visible solitary conidiomata at maturity on all media.
Notes: Diaporthe racemosae is phylogenetically close but clearly differentiated from D. schini based on ITS, tef1, tub2, his3 and cal sequence similarity (98 %, 94 %, 98 %, 94 %, and 96 %, respectively). Moreover, D. racemosa produces only alpha conidia, while D. schini produces only beta conidia (Gomes et al. 2013).
Authors: V. Guarnaccia, A.R. Wood & P.W. Crous