Setosynnema
Setosynnema D.E. Shaw & B. Sutton, Bot. J. Linn. Soc. 91: 33 (1985).
Index Fungorum number: IF 11188; Facesoffungi number: FoF 07569, 3 morphological species (Species Fungorum 2022), 1 species with molecular data.
Colonies effuse, brown to dark brown. Mycelium partly superficial, partly immersed in substratum, comprising branched, septate, tuberculate hyphae. Vegetative hyphae, pale brown to brown. Sexual morph: Unknown. Asexual morph: Conidiomata massive, stout, synnematous, solitary or in aggregates of 1–3, brown, made up of parallel closely packed brown hyphae, with an expanded spore producing head. Setae absent in pure culture but present on natural substrate. Conidiophores arising close to one another, and flock together closely, septate, smooth, sub hyaline to pale brown towards base, hyaline towards apex, sometimes 1–3 irregularly branched, with primary, secondary and tertiary branches, apex somewhat truncate to rounded, invariably with two scars marking position of branches or conidiogenous cells attachment. Conidiogenous cells terminal, apices somewhat rounded or truncate, with two slightly protuberant scars, clavate to cylindrical, hyaline, integrated. Conidia produced in a whitish mass emerging from apex of synnemata, hyaline, sometimes becoming pale whitish brown, acrogenous, filiform, curved, wide near the centre, tapering at each end, but distal end often narrower. Uniseriate chains of 6–8 cells, with 2–4 (mainly 3) of the septa between the middle cells constricted to form a narrow isthmus. The number and position of the constricted septa within the conidium is variable; there are 3(–4) constricted septa near the middle of each conidium, with 0–2 unconstricted septa at the distal end and 2 unconstricted septa at the proximal end (adapted from Bai et al. 2013).
Type species: Setosynnema isthmosporum D.E. Shaw & B. Sutton
Notes: Setosynnema is characterised by massive, stout, synnematous conidiomata, subhyaline to pale brown conidiophores, clavate to cylindrical, hyaline, integrated conidiogenous cells and acrogenous, filiform, curved, hyaline conidia. Nawawi (1985) found Setosynnema isthmosporum from Malaysia. Matsushima (1996) reported Setosynnema isthmosporum from Japan. Marvanová and Hywel-Jones reported Setosynnema isthmosporum from Thailand. Seifert (in Bai et al. 2013) considered Synnematophora as a synonym of Setosynnema based on the presence of setae. Bai et al. (2013) described S. yunnanense from decaying leaves in China based on morphology, namely the synnematous conidiomata and filiform septate conidia with strong constrictions at some septa with the central cells, connected by narrow isthmi. Setosynnema species are differentiated based on conidial size and number of septa (Bai et al. 2013). Bai et al. (2013) found no setae in the pure culture of S. yunnanense as was reported for S. isthmosporum but he did observe it on decaying leaves from which the type species was isolated. Bai et al. (2013) suggested that the variability in setal production might be a differentiating character of Setosynnema as was earlier proposed by Marvanová (2011). Bai et al. (2013) treated Setosynnema as genus incertae sedis. Setosynnema resembles Phalangispora in having similar sporodochia bearing a few dark setae but differs in having unbranched conidia while those of Phalangispora are branched (Guo et al. 2019). Guo et al. (2019) confirmed the placement of Setosynnema in Wiesneriomycetaceae based on morphology and multigene analyses of LSU, SSU, RPB2 and TEF1 sequence data. Setosynnema is morphologically and phylogenetically a distinct genus in Wiesneriomycetaceae. Molecular data is available for only S. yunnanense (LSU, SSU, RPB2 and TEF-1). More collections with DNA sequence data will help establish the relationship of Setosynnema with other genera in Wiesneriomycetaceae.
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