Deciphering Fusarium-Banana Interactions in Resistant and Susceptible Banana Cultivars Using a GFP-Tagged Subtropical Race 4 Strain of Fusarium oxysporum f. sp. cubense

Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is a major disease affecting banana production around the globe. To study the movement of Foc in planta and investigate potential physical mechanisms of deterrence, the roots of a set of banana cultivars were challenged with a GFP-tagged subtropical race 4 strain of Foc. These plants included susceptible and resistant varieties including the plantain 'FHIA25' (AAB), dessert hybrids 'Lady Finger' (AAB), 'FHIA02' (AAAA), as well as the industry preferred Cavendish line, 'Williams' (AAA), and its somaclone derivative 'GCTCV119' (AAA). GFP localisation in planta confirmed that Foc can infect all four cultivars. Its movement through roots to the rhizome and to the aerial parts of the plants was evident. Tyloses formation in the root vasculature was also detected by GFP auto-fluorescence and further confirmed using scanning electron microscopy. While tyloses formation did not prevent colonisation and infection, their formation restricted the fungus within the xylem vessels, slowing its proliferation. This mechanism may be an important factor in providing plant host tolerance to Foc but it doesn't provide complete immunity. Fluorescently tagged Foc is a useful tool for understanding the infection process of the Fusarium wilt disease of banana and aiding in the integrated management of this important disease.