The colonization of wheat stems and subsequent perithecium development by Gibberella zeae (Anamorph Fusarium graminearum)

A devastating pathogen of wheat, Triticum aestivum, is the head blight fungus, Gibberella zeae. Sexual spores of this fungus develop on cereal debris remaining in the field following harvest and provide the primary inoculum for infection of the next cereal crop. The colonization of vegetative wheat tissue by G. zeae in the green house and perithecium development on stem debris was investigated. To observe the patterns and extent of colonization within wheat stems, plants were inoculated with a fungal strain expressing the endow-green fluorescent protein. For observations of perithecium development, colonized wheat stems from an infected field were returned to a new outdoor plot in mesh bags and collected as perithecia formed. The results of this study showed that stems were systemically colonized following head infections and that this colonization was extensive. Descriptive observations implicated G. zeae as a pathogen that invades the vascular system and indicated that host anatomy was important to the development of disease. Perithecium formation occurred on segments of all stems placed in the field and was in close association with specific cell types of the wheat stem epidermis. The characterization of possible resistance mechanisms, systemic colonization and role of host anatomy in association with potential inoculum development are discussed.