Dictyosporium palmae Abdel-Aziz
Index Fungorum number: IF552328; Facesoffungi number: FoF 02492
Etymology: From date palm, the host.
Holotype: CBS-H 22129; Ex-type culture: CBS 139630 = MF3178
Saprobic on submerged decaying fronds of Phoenix dactylifera (date palm). Sexual morph: Undetermined. Asexual morph: Mycelium immersed in the substrate, hyaline, 2.5−4 μm thick, septate. Conidiomata on the natural substrate sporodochial, loose, scattered, shining black, one to 10 cm in length. Conidiophores micronematous, hyaline to light-brown in color, 0–2 septate, 22–40 × 4–5 μm. Conidiogenous cells monoblastic, determinate, yellow-brown to brown in color, sub- globose to ovate in shape, thin-walled, 10–17 × 7–10 μm. Conidia solitary, digitate, complanate, obclavate in shape with rounded base and tapered tip, 75–165 × 15–33 μm (x̄ = 107.02 × 26.4 μm, n = 60), dark-brown to black, consisting of 95–144 cells, individual cells are cylindrical, elongated, 5–7 μm tall, 2.5–4 μm wide, arranged in 3–6 compact rows, 17–26 cells per row, the inner rows nested within the outer rows that mostly shorter than inner ones, tips of some rows are equipped with gelatinous, hyaline, rounded appendages or hyaline, long, hypha-like appendages up to 50 μm long and 3 μm thick or gelatinous caps to the whole conidial tip. (Descriptions from Abdel-Aziz 2016)
Culture characters: Conidia germinating on PDA within 24 h and several germ tubes produced from each conidium. Colonies 30 mm diam. in two weeks at 23ºC, produce white mycelium with orange liquid droplets on its surface with yellow to orange exudates. Sporulating after 3 months incubations and produce conidia similar in shape and size to those recorded on natural wood.
Material examined: EGYPT, Sohag, River Nile, on submerged decaying fronds of Phoenix dactylifera L. (Arecaceae), 14 August 2014, F.A. Abdel-Aziz, CBS-H 22129, holotype; ex-type living culture, CBS 139630 = MF3178.
Notes: Phylogenetic analyses of LSU rDNA placed Dictyosporium palmae in Dictyosporium sensu stricto along with the type species D. elegans in a highly supported clade with D. digitatum and D. stellatum (Abdel-Aziz 2016). Dictyosporium palmae differs from D. digitatum by having longer and narrower conidia (75−105 × 18−32 μm vs. 46.5−88 × 26−46 μm) and a fewer cell rows (4−6 vs. 6−8 rows) for D. palmae and D. digitatum respectively (Goh et al. 1999). Dictyosporium palmae differs from D. stellatum by having larger sporodochia (up to 10 cm length vs. 7 mm diam), narrower conidia (75–165 × 15–33 μm vs. 50–175 × 27.5–52.5 μm), fewer cell rows (3−6 vs. 5–7) for D. palmae and D. stellatum respectively. Conidial appendages are absent in D. stellatum and their conidial cells are discoid or doliiform. Conidial cells in D. palmae are cylindrical or elongate in shape and conidia with appendages (Crous et al. 2011). Dictyosporium sensu stricto comprises the type species D. elegans and sixteen taxa which include fifteen asexual and two sexual species. Fungi belong to Dictyosporium sensu stricto are characterized by having effused and scattered colonies, pleurogenous irregular conidiophores, and olive to brown conidia with or without appendages. The two sexual morph strains are basal to the asexual strains and might represent a new genus (Boonmee et al. 2016). (Notes from Abdel-Aziz 2016)
Abdel-Aziz FA (2016) Two new cheirosporous asexual taxa (Dictyosporiaceae, Pleosporales, Dothideomycetes) from freshwater habitats in Egypt. Mycosphere 7:448–457
Boonmee, S., D’souza, M.J., Luo, Z. et al. Dictyosporiaceae fam. nov. Fungal Diversity 80, 457–482 (2016). https://doi.org/10.1007/s13225-016-0363-z
Fig 1. Dictyosporium palmae (holotype). a Diffuse sporodochia on wood, b-f. Variously shaped conidia, g. Young conidium, f,g. Conidia from pure culture, conidiophores (arrowed), h-k. Magnified apical part of the conidia showing variously shaped conidial appendages. Conidial appendages can be globose hyaline appendage surrounded by mucilaginous sheath (in h, j, arrowed), mucilaginous cap (in k, arrowed) or long, hyaline, hyphae-like (in f, j, arrowed). Scale bars: a = 150 μm, b-f = 10 μm, g-k = 5 μm. (Abdel-Aziz 2016)