Pseudothecia

Pseudothecium (plural pseudothecia) is a type of sexual fruiting body, or ascoma, found in some Ascomycota, most notably within the Dothideomycetes. It consists of a relatively enclosed, often dark and compact structure that bears asci inside one or more locules. The pseudothecial wall is typically multilayered and tissue-like, and the overall form is commonly flask-shaped or globose, sometimes embedded in plant tissue such as leaf litter or lesions.

Within the pseudothecium, asci line the inner surfaces of the locules. The asci are usually bitunicate, meaning they have two functional walls, and they produce ascospores that are released when maturity is reached. Release often occurs through a slit-like opening or ostiole at the apex of the structure, allowing spores to disperse to new substrates via wind or water splash. This form of ascoma is considered distinct from true perithecia and apothecia due to differences in wall development and locule arrangement, hence the term pseudothecium.

Ecologically, pseudothecia are important for the sexual phase of many plant-pathogenic fungi and other saprotrophs. They contribute to genetic diversity and long-distance spore dispersal, often appearing on diseased or fallen plant material and continuing the life cycle of the organism under suitable environmental conditions. Pseudothecia thus play a key role in the epidemiology of several crop diseases and in the broader ecology of leaf- and stem-inhabiting fungi.