A scanning electron microscope study of interactions between micro-organisms andGaeumannomyces graminis (Syn.Ophiobolus graminis) on wheat roots.

Roots of wheat grown in unsterilized sand inoculated withGaeumannomyces graminis (Sacc.) von Arx and Olivier were examined by scanning electron microscopy. Healthy roots had a mucilaginous covering and were sparsely colonized by bacteria, but asG. graminis colonized the roots the mucilage disappeared and the numbers of bacteria on the surface increased. Lysis of the hyphae occurred, apparently caused by bacteria that colonized the hyphae. Inoculation of wheat in axenic culture with a strain ofPseudomonas fluorescens that was antagonistic toG. graminis in agar gave some protection against the pathogen; lysis of hyphae was observed where protection occurred.