Pleosporales » Roussoellaceae


Immotthia M.E. Barr, Mycotaxon 29: 504 (1987).

Index Fungorum number: IF 25106; Facesoffungi number: FoF 08362, 2 morphological species (Species Fungorum 2022), no molecular data available.

Hyperparasitic or saprobic on decorticated wood. Sexual morph: Hypostroma dark brown to black, crust under ascomata, patch-like, composed of thick-walled cells of textura angularis, covering the surface of host stromata, difficult to distinguished from the peridium of ascomata, sometimes forming dark brown hyphae at the lowest layer penetrated with the host of Hypoxylon. Ascomata dark brown to black, subglobose to obpyriform, or inequilateral, gregarious to densely aggregated, superficial, uniloculate, or carbonaceous when dry, glabrous, surface rough with protruding cells, arising from a large hypostroma, usually with a pore-like, inconspicuous ostiole or minute papilla. Peridium thin- to thick-walled, of unequal thickness, composed of several layers, inner layers comprising hyaline to dark brown, pseudoparenchymatous cells, of textura angularis, outer layers composed of thick, dark brown to black cells, arranged in a textura angularis. Hamathecium composed of dense, septate, branched, anastomosing, cellular pseudoparaphyses embedded in a gelatinous matrix. Asci (4–) (6–)–8-spored, bitunicate, fissitunicate, cylindrical or cylindric-clavate, subsessile to short-pedicellate with obtuse knob-like or furcate pedicel, apically rounded with a well-developed ocular chamber. Ascospores overlapping 1–2-seriate, pale yellowish to brown, or reddish brown, ellipsoidal to fusiform, with rounded ends,uniseptate, asymmetrical, with the upper cell slightly larger than the lower cell, slightly constricted at the septum, smooth- to rough-walled, verrucose. Asexual morph: Coelomycetous, chaetophoma-, coniothyrium-, microsphaeropsis-, or pyrenochaeta-like, associated with the sexual morph on natural substrate. Conidiomata pycindial, similar to ascomata but differ in having a smaller size, black, carbonaceous, immersed to erumpent, becoming superficial, globose to obpyriform, uni- to multiloculate, glabrous, with indistinct ostiolate. Pycnidial wall thin- to thick-walled, composed of several layers of brown to dark brown pseudoparenchymatous cells, of textura angularis. Conidiophores reduced to conidiogenous cells. Conidiogenous cells enteroblastic, phialidic, discrete, determinate, ampulliform, or cylindric, smooth, hyaline, with minute collarette and conspicuous periclinal thickening. Conidia ellipsoidal, rounded at both ends, one-celled, at first hyaline, becoming brown at maturity, smooth-walled or finely verrucose (adapted from Jiang et al. 2021).

 Type species: Immotthia atrograna (Cooke & Ellis) M.E. Barr

Notes: Immotthia is characterised by dark brown to black hypostroma, dark brown to black, subglobose to obpyriform, or inequilateral ascomata, cylindrical or cylindric-clavate asci and overlapping 1–2-seriate, pale yellowish to brown, or reddish brown, ellipsoidal to fusiform,uniseptate ascospores. Barr (1993) confirmed that the two taxa I. hypoxylon and I. atrograna are conspecific based on morphological re-examination. Barr (1987a, b) assigned Immotthia to Dacampiaceae and this was followed by Akulov and Hayova (2016). Jaklitsch et al. (2002) formally synonymized I. hypoxylon under I. atrograna based on priority. Barr (2002) transferred Immotthia to Teichosporaceae based on the combination Immotthia atroseptata (Piroz.) M.E. Barr. The asexual morph of Immotthia has been reported as coelomycetous, and identified as Coniothyrium parasitans but this relationship needs to be confirmed based on DNA sequence data (Hyde et al. 2017; Hongsanan et al. 2020a). The asexual morph of Immotthia is characterised by enteroblastic, phialidic, doliiform to ampulliform, or cylindrical, smooth, hyaline conidiogenous cells bearing brown, ellipsoidal, smooth, and aseptate conidia (Hyde et al. 2017; Hongsanan et al. 2020a; Jiang et al. 2021). Hyde et al. (2017) tentatively placed Immotthia in Roussoellaceae based on morphology such as asci, ascospores characters and coelomycetous asexual morph and this was followed by Doilom et al. (2018) and Hongsanan et al. (2020a). Jiang et al. (2021) introduced the third species I. bambusae from dead culms of bamboo (Poaceae) in Thailand based on morphology and phylogeny. According to the phylogenetic analysis of Jiang et al. (2021). Immotthia is closely related to Pseudocoleophoma in Dictyosporiaceae. Immotthia differs from Pseudocoleophoma in having dense, superficial ascomata on hypostoma, with cylindrical to cylindric-clavate asci, ellipsoidal to fusiform, light brown to reddish brown, asymmetrical ascospores, without a mucilaginous sheath while Pseudocoleophoma has scattered or clustered, immersed to erumpent ascomata, with cylindrical to clavate asci, fusiform, hyaline ascospores, enclosed in a mucilaginous sheath (Tennakoon et al. 2019; Li et al. 2020). Members of Immotthia are hyperparasites on hypoxylon-like stroma while species of Pseudocoleophoma are saprobic in terrestrial environment (Jayasiri et al. 2019; Jiang et al. 2021). The asexual morph of Immotthia can be differentiated from Pseudocoleophoma based on the multiloculate, carbonaceous conidiomata and ellipsoidal, brown, aseptate conidia (Hyde et al. 2017; Jiang et al. 2021) while conidiomata of Pseudocoleophoma are uniloculate and produce cylindrical to subcylindrical or fusiform, hyaline, 0–1-septate conidia. Immotthia is morphologically and phylogenetically a distinct genus in Dictyosporiaceae.


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