Scolecobasidium constrictum E.V. Abbott, Mycologia 19(1): 30. 1927.

Song, Shuang, Li, Meng, Huang, Jun-En & Liu, Fang, 2023, Two new species of Scolecobasidium (Venturiales, Sympoventuriaceae) associated with true mangrove plants and S. terrestre comb. nov., MycoKeys 96, pp. 113-126 : 113

Scolecobasidium constrictum E.V. Abbott, Mycologia 19(1): 30. 1927.

Ochroconis constricta ≡ Ochroconis constricta (E.V. Abbott) de Hoog & Arx, Kavaka 1: 57. 1974.

Dactylaria constricta ≡ Dactylaria constricta (E.V. Abbott) D.M. Dixon & Salkin, J. Clin. Microbiol. 24: 13. 1986.

Type.

USA Louisiana, from soil, 1927, E.V. Abbott ex-type culture CBS 202.27 = MUCL 9471 (metabolically inactive) .

Notes.

Scolecobasidium constrictum was introduced at the same time as the generic type of Scolecobasidium , S. terreum , by Abbott (1927). Later, Heterosporium terrestre was treated as a synonym of S. constrictum due to their similar morphological characteristics ( Barron and Busch 1962). Their original descriptions differ, however, in that H. terrestre produces rough conidia and variable conidiophores both in shape and size, and has occasional phragmospores. Therefore, Barron (1962) thought that Abbott described only a facet of S. constrictum and emended the species description. Subsequently, Ochroconis was introduced to accommodate species with sympodial conidiogenesis and unbranched, subspherical to cylindrical or clavate, melanised conidia, and S. constrictum was transferred to this genus as O. constricta and designated as the generic type ( De Hoog 1973).

With the help of molecular analyses, Shen et al. (2020) synonymized Ochroconis under Scolecobasidium , and S. constrictum should be resurrected as a result. We observed that the ex-type cultures of H. terrestre (CBS 211.53) and S. constrictum (CBS 202.27) were separated into two distinct clades with relatively long branches in the current study (Fig. 1 ) and sequences similarities between the two species were very low (LSU: 98.7%; ITS: 88%, tef1 -α: 85%, tub2: 79%). Since S. constrictum (CBS 202.27) is now sterile ( Shen et al. 2020), we could only make a detailed morphological comparison among multiple descriptions of ex-type cultures of H. terrestre (CBS 211.53) and S. constrictum (CBS 202.27) ( Abbott 1927; Atkinson 1952; Barron and Busch 1962; Samerpitak et al. 2014), and found that the two fungi were morphologically different in the shape (oval to ovate, short-cylindrical and long cylindrical to sole-shaped in H. terrestre vs. echinulate to verrucose in S. constrictum ) and number of septa (0-3 vs. 0-1) in the conidia, as well as the size of conidiophores (2-31.5 × 1.5-2.5 μm vs. 5-8 × 2-2.5 μm). Based on morphology combined with the phylogeny, we consider that H. terrestre R.G. Atk. should not be treated as a synonym of S. constrictum , and a new combination Scolecobasidium terrestre comb. nov. is proposed in this study.

In addition, the type strain of S. constrictum should be CBS 202.27, rather than CBS 211.53, which was incorrectly listed in tables 2, 3 and figs 1, 2 in Wei et al. (2022).

Figures

Figure 1. Phylogenetic tree of Scolecobasidium calculated with a maximum likelihood analysis of the combined ITS, LSU, tef 1 - α, and tub 2 sequences alignment. The tree was rooted with Verruconis calidifluminalis (CBS 125818). Bootstrap values (ML> 50 %) and Bayesian posterior probabilities (PP> 0.90) are shown at the nodes in the order of ML / PP. T indicates ex-type strains. The novel taxa and new combination are showed in bold. The scale bar represents the expected changes per site.