Pleosporales » Pleosporaceae

Pleoseptum

Pleoseptum A.W. Ramaley & M.E. Barr, Mycotaxon 54: 76 (1995).

Index Fungorum number: IF 6197; Facesoffungi number: FoF 07387, 1 morphological species (Species Fungorum 2022), no molecular data available.

Saprobic on leaves of Yucca baccata Torr. Sexual morph: Ascomata scattered, solitary, immersed, visible as numerous black spots on host surface, uniloculate, globose to ovoid or conoid, dark brown to black, glabrous, with centrally opening ostiole penetrating the host epidermis. Peridium thick-walled, of unequal thickness, broad at the apex, composed of two layers of thickened pseudoparenchymatous cells, outer layer comprising several layers of thick-walled cells, arranged in a textura angularis, brown to dark brown, inner layers comprising several layers of thin-walled cells, hyaline, arranged in textura angularis. Hamathecium composed of numerous, 2–3 μm wide, filiform, distinctly septate, frequently anastomosing, narrow cellular pseudoparaphyses, embedded in mucilaginous matrix. Asci 8-spored, bitunicate, fissitunicate, cylindrical to cylindric-clavate, short pedicellate, apically rounded, with well-developed ocular chamber. Ascospores overlapping 1-seriate, dictyosporous, muriform, ellipsoidal to fusiform or obovoid, brown to dark brown, with 3–5 transverse septa, and 0–2 longitudinal septa, constricted at the central septum, smooth-walled, with distinct mucilaginous sheath. Asexual morph: Conidiomata growing with the sexual state, pycnidial, scattered, solitary to gregarious, immersed, visible as black spots on host surface, uniloculate, globose to ovoid or conoid, brown to dark brown, glabrous, with ostiolar opening penetrating the host epidermis. Conidiomata walls thick-walled, of unequal thickness, broad at the apex, composed of several layers of thickened pseudoparenchymatous cells, arranged in textura angularis, brown to dark brown. Conidiophores discrete, oblong to cylindrical, usually unbranched, hyaline to brown, septate, arising from basal cavity of conidiomata. Conidiogenous cells enteroblastic, annellidic or sympodial. Conidia muriform, oblong to obovoid or ellipsoidal with rounded or obtuse ends, with truncate base, initially hyaline, becoming brown to reddish-brown or dark brown at maturity, mostly with 3–5 transverse septa and 1–3 longitudinal septa, with several segments, smooth-walled (adapted from Phookamsak et al. 2014).

Type species: Pleoseptum yuccaesedum A.W. Ramaley & M.E. Barr

Notes: Pleoseptum is characterised by scattered, solitary, immersed ascomata, cylindrical to cylindric-clavate asci and 1-seriate, dictyosporous, muriform, ellipsoidal to fusiform or obovoid, brown to dark brown ascospores. The asexual morph is characterised by pycnidial, scattered conidiomata, enteroblastic, annellidic or sympodial conidiogenous cells, and muriform, oblong to obovoid or ellipsoidal conidia with rounded or obtuse ends and 5 transverse septa and 1–3 longitudinal septa. Lumbsch and Huhndorf (2010), Zhang et al. (2012) and Hyde et al. (2013) tentatively placed Pleoseptum in Phaeosphaeriaceae based on morphology. Pleoseptum resembles Leptosphaeria based on its peridium structure (Ramaley & Barr 1995, Zhang et al. 2012). Pleoseptum has dictyosporous conidia while Leptosphaeria has amerosporous conidia (Ramaley & Barr 1995, Hyde et al. 2013). Pleoseptum is also similar to Dematiopleospora in having muriform ascospores (Wanasinghe et al. 2014) but differs by the thick peridium structure comprising heavily pigmented, thick-walled cells with ostiole while in Dematiopleospora, the peridium is thinner, comprising lighter pigmented, thin-walled cells, with thick periphyses in the ostioles. Phookamsak et al. (2014) excluded Pleoseptum from Phaeosphaeriaceae and tentatively placed it in Pleosporaceae based on the narrow pseudoparaphyses, and camarosporium-like asexual morph. Ramaley and Barr (1995) referred Camarosporium yuccaesedum as the asexual morph of Pleoseptum yuccaesedum based on the co-occurrence of both species on the same host. The sexual and asexual relationship was confirmed by culture comparisons with conidia formed in culture from a sexual state (Ramaley & Barr 1995). Camarosporium yuccaesedum is unique and differs from Camarosporium sensu stricto in producing microconidia (Crous et al. 2013, Wijayawardene et al. 2014). Molecular data is lacking for Pleoseptum hence, fresh collections and DNA sequence data are required to confirm the taxonomic placement of the genus.

 

Recent News

Recent paper to be published

Recent Genus

Nothocladosporium
Phillipsiella
Curreya

Recent Species

Nothocladosporium syzygii
Phillipsiella atra
Curreya conorum