Characterisation of early events in banana roots infected with green fluorescent protein-tagged Fusarium oxysporum f. sp. cubense .

摘要

The infection of banana by Fusarium oxysporum f. sp. cubense (Foc) can result in variable disease development, ranging from no symptoms to severe rotting and wilting. Understanding the infection process of Foc is a prerequisite for effective control and management of this disease. To visualise the infection process, we used a green fluorescent protein (GFP)-tagged strain of tropical race 4 of Foc and characterised early events in infection and disease development in Cavendish plantlets. With fluorescence microscopy, the labelled strain was observed to infect roots, colonise the root mesocotyl and, finally, the plant pseudostem. These studies indicated that the preferential colonisation sites on the root surface were grooves along the junction of the epidermal cells. This resulted in mosaic patterns of infection that developed after specific epidermal and cortical cells were infected by intercellular hyphae, while surrounding cells remained free of fungus. Finally, hyphae developed inside xylem vessels of fully colonised, rotted roots. Specific infection structures, such as appressoria, were not observed. These observations clarify events that occur after Cavendish is infected by this important pathogen and provide new clues to explore infection mechanisms of Foc. More detailed knowledge of the host-pathogen interaction could help develop more efficient ways to control the disease.