Histological Dissection of Fusarium-Banana Interaction Using a GFP-Tagged Subtropical Race 4 Strain of Fusarium oxysporum f. sp. cubense on Banana Cultivars with Differing Levels of Resistance

Fusarium wilt, caused by <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> (<i>Foc</i>), poses a significant threat to global banana production. This study used a GFP-tagged subtropical race 4 strain of <i>Foc</i> (GFP-<i>Foc</i>-STR4) to trace the pathogen's movement in different banana cultivars. These include a race 4 resistant cultivar FHIA25 and the Cavendish somaclone 'GCTCV119', as well as susceptible cultivars including 'Lady Finger', 'FHIA02', and 'Williams' Cavendish. GFP localization revealed that GFP-<i>Foc</i>-STR4 was able to infect all tested cultivars, moving from the roots to the rhizome and aerial parts of the plant. Tyloses formation in root and rhizome vasculature, visualised with GFP autofluorescence and confirmed by scanning electron microscopy, was found to restrict <i>Foc</i> within the xylem vessels, slowing its spread but not fully preventing infection. This containment mechanism contributes to the host tolerance of 'FHIA25' and 'GCTCV119', though it does not confer complete immunity. The use of the fluorescently tagged <i>Foc</i> strain provides valuable insight into the infection process, and supports efforts in the integrated management of Fusarium wilt of banana.