Ascus apical apparatus and ascospore characters in Xylariaceae

Abstract

Members of Xylariaceae (Ascomycota) are recognized and classified mainly on the morphological features of their sexual state. In a number of genera high morphological variation of stromatal characters has made confident recognition of generic and specific boundaries difficult. There are, however, a range of microscopical characteristics which can in most cases make distinctions, especially at generic level, even in the absence of molecular data. These include details of the apical apparatus in the ascus (e.g. disc-shaped, inverted hat-shaped, rhomboid, composed of rings, amyloid, non-amyloid); position and length of the germ slit; and presence and type of ascospore wall ornamentation as seen by scanning electron microscopy (SEM). Unfortunately many of the classical studies on xylariaceous genera omitted these features and were undertaken long before the development of scanning electron microscopy. More recent studies have, however, demonstrated their value as diagnostic characters in the family. Camillea is for example, instantly recognizable by its rhomboid or diamond shaped apical apparatus, and the distinctive inverted hat or urniform type is usually prominent in Xylaria, Rosellinia, Kretzschmaria, and Nemania. At least six categories of apical apparatus based on shape and size can be recognized. Ascospore ornamentation as seen by SEM has been exceptionally useful and provided the basis for separating Camillea from Biscogniauxia and other xylariaceous genera.

Diversity and Taxonomy of Endophytic Xylariaceous Fungi from Medicinal Plants of Dendrobium (Orchidaceae)

“…The members of this family are usually considered to be saprophytic, but some taxa have been described as endophytic or pathogenic [16], [17], with a few species being associated with termites [18]. In the past thirty years, a number of studies have reported on the taxonomy, phylogenetic reconstruction, ecology, and relationship between xylariaceous fungal teleomorph and anamorph stages, including work on endophytic xylariaceous fungi [19]–[28]. Moreover, a series of new compounds have been isolated from Xylariaceae species and demonstrated good antimicrobial or anticancer bioactivity, particularly endophytic Xylaria [29]–[32].…”

Morpho-Molecular Characterization Reveals a New Genus, Three Novel Species and Two New Host Records in Xylariomycetidae

“…Stromatic characteristics, such as the length of the ascus stipe [ 51 ], amyloid reactions [ 54 ], and the shape and size of the ascus apical ring [ 55 ], are used to delimit xylarialean taxa. The number of ascospores per ascus [ 56 ], color [ 57 ], septation [ 23 ], appendage [ 54 , 58 ] and character of the germ slit [ 1 , 12 ] also play a vital role in the identification of xylarialean taxa.…”

Hypoxylon (Xylariaceae, Ascomycota) from Western Paraná, Brazil

“…Microscopic features were examined in 10 % KOH, and measured based on distilled water preparations; asci were observed in cotton blue, except for the apical ring, examined on Melzer's reagent. Ascospores were analyzed under scanning electron microscopy (SEM) Jeol JSM-6360LV, at the Center of Electron Microscopy (CME) of the Paraná University, following Suwannasai et al (2012). All specimens are preserved at the Herbarium of Palotina Campus (HCP) and holotype at the Herbarium of the National Botanic Department of the Paraná University (UPCB).…”