Pleosporales » Dictyosporiaceae

Digitodesmium

Digitodesmium P. M. Kirk

 

Saprobic on submerged bamboo, wood in freshwater or decaying wood, soil in terrestrial habitats. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Conidiomata sporodochial, punctiform, pulvinate, scattered, pale brown to brown. Mycelium mostly immersed, composed of branched, septate, thin-walled, smooth, pale brown hyphae. Conidiophores semi-macronematous, mononematous, fasciculate, composed of moniliform, pale brown, septate, smooth hyphae. Conidiogenous cells holoblastic, monoblastic, integrated, terminal, determinate, globose to doliiform, minutely cicatrized. Conidia acrogenous, solitary, dry, digitate, cheiroid, slightly divergent arms, euseptate, some with a hyaline gelatinous cap at the apex (Kirk 1981; Boonmee et al. 2016).

 

Type species: Digitodesmium elegans P.M. Kirk

 

Notes: Digitodesmium is unique by its digitate conidia and moniliform conidiophores (Kirk 1981; Boonmee et al. 2016). Tsui et al. (2006) indicated that Digitodesmium might be a synonym of Dictyosporium because the phylogenetic position of Digitodesmium was within Dictyosporium, but with low bootstrap support. A similar result was shown in Cai et al. (2008). Digitodesmium was distinguished from Dictyosporium by its divergent conidial arms which were considered as an artificial feature by Tsui et al. (2006) and Cai et al. (2008). Boonmee et al. (2016) introduced family Dictyosporiaceae to accommodate most cheirosporous hyphomycete genera and accepted Digitodesmium as a distinct genus based on multigene phylogenetic analyses. We think that the moniliform conidiophores of Digitodesmium are also important to distinguish this genus. Three freshwater Digitodesmium species morphologically fit well with the generic concept of Digitodesmium in producing divergent conidial arms (Ho et al. 1999; Cai et al. 2002, 2003). The placement of D. heptasporum L. Cai & K. D. Hyde and D. recurvum W. H. Ho et al. needs to be confirmed with molecular data. (Notes from Dong et al. 2020)

 

List of freshwater Digitodesmium species

*Digitodesmium bambusicola L. Cai, K. Q. Zhang, McKenzie, W. H. Ho & K. D. Hyde, Nova Hedwigia 75: 528 (2002)

Freshwater distribution: Philippines (Cai et al. 2002)

Digitodesmium heptasporum L. Cai & K. D. Hyde, Sydowia 55: 133 (2003)

Freshwater distribution: Yunnan, China (Cai et al. 2003)

Digitodesmium recurvum W. H. Ho, K. D. Hyde & Hodgkiss, Mycologia 91: 900 (1999)

Freshwater distribution: China (Ho et al. 1999)

 

Key to freshwater Digitodesmium species

1. Conidia with appendage....................................................... D. bambusicola

1. Conidia without appendages....................................................................... 2

2. Conidia 30–45 × 12–21 μm......................................................... D. recurvum

2. Conidia 50–75 × 32.5–70 μm................................................. D. heptasporum

 

References

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

Cai L, Guo XY, Hyde KD (2008) Morphological and molecular characterisation of a new anamorphic genus Cheirosporium, from freshwater in China. Persoonia 20:53–58

Cai L, Zhang KQ, McKenzie EHC, Ho WH, Hyde KD (2002) Acrodictys liputii sp. nov. and Digitodesmium bambusicola sp. nov. from bamboo submerged in the Liput River in the Philippines. Nova Hedwigia 75:525–532

Cai L, Zhang KQ, McKenzie EHC, Hyde KD (2003) New species of Dictyosporium and Digitodesmium from submerged wood in Yunnan, China. Sydowia 55:129–135

Dong W, Wang B, Hyde KD, McKenzie EHC, Raja HA, Tanaka K, Abdel-Wahab MA, Abdel-Aziz FA, Doilom M, Phookamsak R, Hongsanan S, Wanasinghe DN, Yu X-D, Wang G-N, Yang H, Yang J, Thambugala KM, Tian Q, Luo Z-L, Yang J-B, Miller AN, Fournier J, Boonmee S, Hu D-M, Nalumpang S, Zhang H (2020) Freshwater Dothideomycetes. Fungal Divers 105:319–575

Ho WH, Hyde KD, Hodgkiss IJ (1999) Digitodesmium recurvum, a new species of chirosporous hyphomycete from Hong Kong. Mycologia 91:900–904

Kirk PM (1981) New or interesting microfungi II. Dematiaceous hyphomycetes from Esher Common. Surrey. Trans Brit Mycol Soc 77:279–297

Tsui CKM, Berbee ML, Jeewon R, Hyde KD (2006) Molecular phylogeny of Dictyosporium and allied genera inferred from ribosomal DNA. Fungal Divers 21:157–166

 

Fig 1. Digitodesmium spp. a–c. D. recurvum (redrawn from Ho et al. (1999), HKU(M) 4552, holotype). a. Conidiophore bearing conidium, b. Conidium, c. Conidium at the basal portion, d. D. bambusicola (redrawn from Cai et al. (2002b), PDD 74494, holotype), d. Conidium with apical or subapical appendages. Scale bars: a–d = 10 μm. (Dong et al. 2020)

 

 

Recent Genus

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