Leptosphaeria doliolum (Pers.) Ces. & De Not., Comm. Soc. crittog. Ital. 1(4): 234 (1863)

            ≡ Sphaeria doliolum Pers., Icon.Desc.Fung. Min. Cognit. (Leipzig) 2: 39 (1800)

Saprobic on stems and leaves of herbaceous or woody plants in terrestrial habitats.Sexual morph: Ascomata 340–460 μm high × 360–500 μm diam. (x̅ = 390 × 440 μm, n = 10), solitary, scattered or in small groups, erumpent to superficial, globose to subglobose, smooth, easily removed from the host substrate, with a flattened base, black, coriaceous, usually with 2–4 ring-like ridges surrounding the ascomata surface, ostiolate. Ostiole apex with a conical, shiny, welldeveloped papilla, ostiolar canal filled with periphyses, dark brown to black. Peridium 85–110 μm wide at sides, thinner at the apex, comprising two types of cells, outer layer composed of small thick-walled cells of textura angularis, cell wall up to 8 μm thick, surface heavily pigmented and inner lightly pigmented, apex cells smaller, walls thicker, and cells more heavily pigmented, inner layer composed of subhyaline relatively thinner-walled cells of textura angularis, 3–6 μm diam., wall up to 5 μm, cells near the base larger and wall thinner and paler. Hamathecium of 1.5–3 μm (x̅ = 2.5 μm, n = 10) wide, septate, and cellular pseudoparaphyses, branching and anastomosing, embedded in a gelatinous matrix. Asci 105–150 × 7–10 μm (x̅ = 130 × 8 μm, n = 20), 8-spored, bitunicate, fissitunicate, cylindrical, with short, bulbous pedicel, rounded at the apex, with a distinct ocular chamber. Ascospores 25–30 × 4–6 μm (x̅ = 27 × 5 μm, n = 30), uni- or bi-seriate, partially overlapping, reddish to yellowish brown, narrowly fusoid with sharp to narrowly rounded edges, 3-septate, constricted at each septum, cell above central septum widest, smooth-walled, lacking a mucilaginous sheath, guttulate. Asexual morph:undetermined.

Material examined: ENGLAND, Kellie Castle, on dead stem, 25 June 2012, J.E. Taylor, MFLU 15-1875.

 

Fig .Leptosphaeria dolioluma, b. Appearance of ascomata on host substrate.c. Section of ascoma (TS). d. Close up of peridium. e Cellular pseudoparaphyses. f–h. Asci with 8-spores. i–m. Brown ascospores. Scale bars: c = 200 µm, d = 200 µm, e = 20 µm, fh = 60 im = 10 µm.

Notes: Leptosphaeria was introduced by Cesati and de Notaris (1863) with 26 species and L. doliolum was treated as the lectotype species for the genus (Shearer et al. 1990). Material observed by Persoon (1800), based on collection of 12 specimens of Sphaeria doliolum present in Nationaal Herbarium Netherlands, Leiden University (L) was selected to lectotypify S. doliolum and thereby L. doliolum (Shearer et al. 1990). Leptosphaeria was described with ascospores being ellipsoid or fusoid, with one to many septa, and hyaline to dark brown (Crane and Shearer 1991). Höhnel (1909) divided the genus based on centrum structure into three genera, viz. Leptosphaeria, Scleropleella and Nodulosphaeria (Zhang et al. 2012). By giving priority to the ascospore characters as well as pseudothecial and centrum structure, Müller (1950) subdivided Leptosphaeria into four sections and this treatment was modified by Munk (1957), who named these four sections as section I (Eu-Leptosphaeria), section II (Para-Leptosphaeria), section III (Scleropleella) and section IV (Nodulosphaeria). The genus has been included in Leptosphaeriaceae (Barr 1987; Eriksson and Hawksworth 1991) or Phaeosphaeriaceae (Eriksson and Hawksworth 1986). Even though Leptosphaeria shares some similar morphological characters with Amarenomyces, Bricookea, Diapleella, Entodesmium, Melanomma, Nodulosphaeria, Paraphaeosphaeria, Passeriniella, Phaeosphaeria and Trematosphaeria, it differs in producing ascomata on dicotyledonous hosts, in having cylindrical asci with short bulbous pedicels and smooth-walled, fusoid, multi-septate ascospores. Recent studies based on multi-gene analysis showed that Leptosphaeria clustered within the order Pleosporales, in the family Leptosphaeriaceae. Species of Leptosphaeria (including the type of Leptosphaeriaceae) and Neophaeosphaeria formed a paraphyletic clade with moderate bootstrap support (Schoch et al. 2009; Zhang et al. 2012; Hyde et al. 2013).