pycnidia

Pycnidium (plural pycnidia) is a type of asexual fruiting body, or conidioma, produced by certain fungi. It is typically flask-shaped or globose and may be embedded in plant tissue or borne on the surface. The interior cavity is lined with conidiogenous cells that produce conidia asexually. Conidia are released through a small opening called an ostiole, allowing dispersal by wind, rain, or mechanical disturbance.

Pycnidia are characteristic of many coelomycete fungi and commonly occur in plant pathogens. They may develop singly or in groups, and often appear as dark, pigmented, dot-like structures on leaves or stems. In culture, pycnidia form under conditions that promote asexual reproduction and can be distinguished from other conidiomata types such as acervuli, which release conidia from a spreading mass, and from sexual fruiting bodies like perithecia or pseudothecia.

Functionally, pycnidia protect developing conidia and coordinate their production for dispersal, contributing to the spread of the fungus in the host or environment. They are part of the asexual life cycle in many fungi and may occur alongside sexual structures in species that have both reproductive modes.

Examples of fungi known to produce pycnidia include species in the genera Phomopsis, Diplodia, and Septoria, among others. The term describes a morphological feature rather than a strict taxonomic grouping, and pycnidia can vary in size, shape, and internal organization across species.