A Scanning Electron Microscope Study of Interactions Between Micro-organisms and Gaeumannomyces graminis (Syn. Ophiobolus graminis) on Wheat Roots

Roots of wheat grown in unsterilized sand inoculated with Gaeumannomyces 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 as G. 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 of Pseudomonas fluorescens that was antagonistic to G. graminis in agar gave some protection against the pathogen; lysis of hyphae was observed where protection occurred.