Studies of Didytmella bryoniae (Auersw.) Rehm: Development in the Host

Growing hyphae of Didymella bryoniae (Auersw.) Rehm are found in the stem tissue of cucumber, and the fungus can colonize nearly all types of tissue. The presence of the pathogen in the lignified elements suggests a spread of the disease up and down from the site of primary infection, even when the stem is strongly decomposed. The fungus dtsplays hyphal dimorphism in the infected tissue and a remarkable feature is stromatic-like structures in the host tissue close to fruiting bodies. Staining reveals no histological host reaction to fungal penetration of cell walls. The pathogen is characterized by the early development of its sexual stage.