Ultrastructural Studies on the Colonization of Banana Tissue and Fusarium oxysporum f. sp. cubense Race 4 by the Endophytic Bacterium Burkholderia cepacia

Colonization on banana roots and on the pathogenic fungus, Fusarium oxysporum f. sp. cubense race 4, causing banana wilt disease, by the endophyte Burkholderia cepacia isolated from asparagus, which might be used as a biological control agent, was investigated with the aid of scanning and transmission electron microscopy. B. cepacia was able to colonize the surface of hyphae of F. oxysporum f. sp. cubense and the fungal macrospores. In vitro colonization ofthe fungus by the endophyte resulted in mycelial deformation with terminal and intercalary swelling. In the banana plant B. cepacia was closely associated with banana roots. A matrix was frequently found to be present between the bacterium and the plant surface. Transmission electron microscopy observations showed that B. cepacia exists mainly in the intercellular space of the banana root tissues.