Ultrastructural features of a Stagonospora species (Ascomycotina) in senescent tissues of perennial ryegrass (Lolium perenne L.)

SUMMARY The pycnidium of a Stagonospora sp. observed in degenerating leaf sheath and blade tissues of Lolium perenne L. contained concentric bodies similar to those found in the mycobiont of several lichens and a few other free‐living ascomycetes. These bodies occurred in vegetative hyphae, hyphae of the pycnidial wall, in conidiogenous cells and in conidia and comprised a central electron‐translucent core surrounded by a granular zone and an outer radially orientated fibrillar or lamellar zone. In some cases the entire body was surrounded by a translucent halo. A second feature of the interwoven hyphae of the pycnidial wall was the occurrence of pores connecting adjacent hyphae. These lateral pores appeared identical to pores in septa between cells of individual hyphae, and like them, were associated with Woronin bodies.