Citation: Pem D et al. (2019) Mycosphere Notes 275-324: A morphotaxonomic revision and typification of obscure Dothideomycetes genera (incertae sedis). Mycosphere 10(1), 1115–1246
Bactrodesmium Cooke, Grevillea 12(no. 61): 35 (1883)
Pathogenic on dead wood. Sexual morph: Undetermined. Asexual morph: Sporodochia scattered, punctiform, dark-brown. Conidiophores macronematous, mononematous packed together closely to form pulvinate sporodochia, unbranched, mid to dark-brown, smooth, septate. Conidiogenous cells integrated, holoblastic, monoblastic, terminal, cylindrical. Conidia oblong-clavate, confluent with the stem, 4 to 6- septate, the lower articulation and the uppermost short, the second from the top very long, solitary, straight to curved, rounded at the tip and truncate at the base, the upper end becoming progressively paler towards the basal cell which is usually sub-hyaline, with a very dark band at the first septum from the top, smooth.
Type species – Bactrodesmium abruptum (Berk. & Broome) E.W. Mason & S. Hughes
Notes – The genus Bactrodesmium is established by Cooke (1883) to accommodate Sporidesmium abruptum Berk. and Br., Sporidesmium spilomeum Berk. and Br. Sporidesmium abruptum was transferred to Bactrodesmium but the binomial was invalidly published. The combination was later validated by Mason & Hughes (1958), and B. abruptum was designated as the lectotype species of Bactrodesmium. Two new species namely, B. opacum and B. clavulatum were later added to the genus Bactrodesmium by Cooke & Harkness (1884). Currently, more than 48 epithets are accommodated in the genus Bactrodesmium (Index Fungorum 2019). The sexual morph is reported to be Stuartella spp. (Wijayawardene et al. 2018). The genus is heterogeneous and includes species with pseudoseptate conidia, such as B. rahnii M.B. Ellis (Ellis 1976) or euseptate, with or without presence of black bands in the septa. They are rarely verrucose as in Bactrodesmium palmicola Mercado, Heredia & J. Mena (Mercado-Sierra et al. 1995) or with longitudinal septa such as Bactrodesmium indicum Reghuveer (Rao 1983). The genus Bactrodesmium is identified by its sporodochial conidiomata and hyaline or brown, simple or branched conidiophores associated with mono- or polyblastic conidiogenous cells (Ellis 1971, Holubova-Jechova 1972). According to a study conducted by Hernandez-Restrepo (2013) based on B. obovatum (FR870265), B. pyriforme (FR870266) and B. pyriforme (HE646637), the genus Bactrodesmium clusters in Sordariomycetes, genera incertae sedis. In the analyses conducted by (Hernandez-Restrepo 2017), Bactrodesmium pallidum (FMR 11345) formed a clade in the Savoryellaceae, Bactrodesmium gabretae (ZK) was basal to Calycina citrigena (ILLS 61033) while Bactrodesmium cubense (CBS 680.96) was basal to Morosphaeria velatispora (KH 218). In our phylogenetic analyses using LSU and ITS sequences available in GenBank, the strain Bactrodesmium gabretae (ZK) is basal to Dermea acerina (CBS 161.38) which is accommodated in Leotiomycetes; Bactrodesmium pallidum (FMR 11345) is basal to Bahusakala longispora (CBS 544.84) in Sordariomycetes while Bactrodesmium cubense (CBS 680.96) is basal to Morosphaeria ramunculicola (BCC 18404) in Morosphaeriaceae (data not shown). The genus Bactrodesmium is polyphyletic and taxonomy is still unresolved because of its potential high diversity and lack of DNA sequences. More cultures and DNA sequences are required to build the phylogenetic tree of Bactrodesmium and resolve its correct taxonomic position. We illustrate the characters of the genus Bactrodesmium by re-examining the type specimen Sporidesmium abruptum Berk. Br. under the code IMI 6833. The genus needs epitypifying or a reference specimen. Based on morphological characters, we retain the genus Bactrodesmium sensu stricto in Dothideomycetes, genera incertae sedis.