Aaosphaeria Aptroot, Nova Hedwigia 60 (3–4): 329 (1995)
Associated with soil. Sexual morph: Ascomata scarce between the predominant pycnidia, only found in subcultures on OA, much smaller than the pycnidia, pyriform or subglobose, usually papillate with a round ostiole which is filled with pseudoperiphyses. Outer wall comprising thin-walled densely to loosely interwoven, septate, branched, dark olivaceous-brown hyphae, forming a textura intricata, composed of thin-walled, brown, usually strongly compressed cells, composed of 3−8 µm wide, hyaline cells is often developed. Asci numerous, more or less parallel or bent towards the papilla, cylindrical or somewhat clavate in the apical part, with a short up to 40 µm long stalk, bitunicate (the outer tunica hardly visible in ripe asci), containing 8 ascospores, monostichous or distichous in the apical part of the ascus. Ascospores ovoid or somewhat fusiform, tapering towards the rounded apex and somewhat truncate at the base, dark brown, with a finely pitted exosporium, one-septate near the middle, not or only slightly constricted at the septum. Paraphysoids very abundant, long and slender and branched in the basal part, reaching into the papilla, not septate or with hardly visible septa. Asexual morph: Pycnidia developing on various media, globose, pyriform or of irregular shape, single or some grown together forming multi-chambered complexes, with flat apex or distinctly papillate, sometimes broadened at the top and disk shaped with round porus which is surrounded by a usually well-developed ring, composed of blackish brown, thick-walled cells at the inner side with hyaline or pale olivaceous periphysis-like cells. Wall comprising two well-differentiated layers: 0−3 cells (5−15 µm) thick outer layer composed of 2−3.5µm wide, rather thick-walled, olivaceous-brown strongly interwoven hyphae, mostly well-developed in the apical region (textura intricata), and a 1−3 cells thick inner layer, composed of thin walled, sub hyaline, isodiametrical or strongly flattened cells. In multi-chambered pycnidia the inner wall layers can merge into the cavity. Conidiogenous cells discrete, hardly differentiated from the inner wall cells, thin-walled, subconical, phialidic, lacking a recognizable collarette and with a minute apical thickening. Conidia aseptate, pale olivaceous-brown, smooth, ellipsoidal or cylindrical, sometimes somewhat inequilateral, apically rounded or one or both ends truncate, aguttulate (Adapted from Van der Aa 1989).
Type species: Aaosphaeria arxii (Aa) Aptroot
Notes: Aaosphaeria resembles Cyclothyrium in having pycnidial conidiomata, phialidic conidiogenesis, a well-developed ostiole and aseptate, brownish conidia, but differs in the stromatic nature of the conidiomata, presence of a well-differentiated ostiole and characteristic textura intricata of the conidiomatal wall. Aaosphaeria was previously placed in Dothideales by Aptroot (1995) and accepted in Dacampiaceae by several authors (Lumbsch and Hundorf 2007; Hyde et al. 2013; Hongsanan et al. 2020a). Aaosphaeria has a “microsphaeropsis-like” asexual morph. Vu et al. (2019) provided sequence data of Aaosphaeria. Molecular markers available for Aaosphaeria are ITS, LSU, SSU, Actin and Calmodulin.