Murramarangomycetales » Murramarangomycetaceae

Phaeothyriolum

Phaeothyriolum Syd., Annls mycol. 36(4): 305 (1938).

= Murramarangomyces Crous, in Crous et al., Persoonia 39: 385 (2017).

Index Fungorum number: IF 3962; Facesoffungi number: FoF 08089, 7 morphological species (Species Fungorum 2022), 4 species with molecular data.

Leaf spots circular, indistinct, confined to one side of the leaf. Mycelium inter epidermal, brown, septate, branched, giving leaf spots a red-purple appearance without any superficial mycelium being present; mycelium aggregating in substomatal cavity, giving rise to suprastomatal ascomata, either on living leaves, or on leaf litter. Sexual morph: Ascomata thyriothecial, in radial orientation or clusters, circular, brown, superficial, flattened, with lobed, smooth to irregular margin of textura epidermoidea or angularis. Asci ellipsoid-obclavate, pedicellate, 8-spored, with small ocular chamber. Pseudoparaphyses hyaline, septate, anastomosing or not, hypha-like, dissolving at maturity, or persistent. Ascospores tri- to multiseriate, hyaline, uniseptate, guttulate, granular, slightly constricted at median septum or not, fusoid-ellipsoid to obovoid, encased in prominent mucoid sheath that is mostly absent at maturity, becoming brown once discharged onto agar. Asexual morph: Mycelium in vitro consisting of hyaline, smooth hyphae, irregular, constricted at septa, forming brown, thick-walled cells that become fertile conidiogenous cells, aggregated in cauliflower-like clusters of brown, doliiform to globose, brown conidiogenous cells, phialidic, giving rise to solitary conidia. Conidia in slimy mass, aseptate, hyaline, smooth, bacilliform (adapted from Crous et al. 2019).

Type species: Phaeothyriolum eucalyptinum Syd.

Notes: Phaeothyriolum is characterised by thyriothecial ascomata, ellipsoid-obclavate, pedicellate, 8-spored asci, hyaline, septate pseudoparaphyses and tri- to multiseriate, hyaline, uniseptate, guttulate ascospores. The asexual morph is characterised by hyaline, smooth hyphae, irregular mycelium, doliiform to globose, brown conidiogenous cells and aseptate, hyaline, smooth, bacilliform conidia. Phaeothyriolum resembles Paramycoleptodiscus but differs in having creeping hyphae that produce grouped brown clusters of phialidic conidiogenous cells which form hyaline, smooth, aseptate conidia (Crous et al. 2017). Wijayawardene et al. (2017) placed Phaeothyriolum in Dothideomycetes genera incertae sedis. Crous et al. (2019) synonymized Murramarangomyces under Phaeothyriolum since M. corymbiae was reported to be the asexual morph of Phaeothyriolum corymbiae. In the phylogenetic analysis of Crous et al. (2019) based on ITS sequence data, four species of Phaeothyriolum clustered together within Dothideomycetes. Phaeothyriolum is morphologically and phylogenetically a distinct and well-defined genus in Murramarangomycetaceae. Molecular markers available for Phaeothyriolum include ITS, LSU and SSU.

 

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