Fig. 1

Role of bikaverin in the vegetative growth and pathogenicity of Fusarium oxysporum f. sp. cubense TR4 (Foc TR4). a Schematic representation of the bikaverin biosynthetic gene cluster in the wild-type (WT) and the FocBik1 knockout mutant (ΔFocBik1). FocBik1, encoding a polyketide synthase, was replaced with a neomycin phosphotransferase II (NPTII) cassette in ΔFocBik1. b Quantification of bikaverin production in WT, ΔFocBik1, and uninoculated control cultures by LC–MS. Bars represent mean peak areas of bikaverin-specific ions. ΔFocBik1 exhibits no detectable bikaverin production. Data are presented as mean ± standard deviations. c Colony morphology of WT, ΔFocBik1, and complemented strain (Res-ΔFocBik1) on complete medium (CM), minimal medium (MM), and under various abiotic stress conditions. d Colony diameter of WT, ΔFocBik1, and Res-ΔFocBik1 after 7 days of growth on CM and MM. e Quantification of conidiation of WT, ΔFocBik1, and Res-ΔFocBik1 cultured in liquid complete medium. f Growth inhibition of WT, ΔFocBik1, and Res-ΔFocBik1 under abiotic stress conditions. Data are presented as mean ± standard deviations. Letters indicate statistical significance determined by one-way ANOVA with Duncan’s multiple range test (P < 0.05). g Disease symptom and index of banana plantlets inoculated with WT, ΔFocBik1, and Res-ΔFocBik1. Representative images of pseudo-stem browning are shown, with the corresponding disease index distribution across plantlets. h Infection and colonization of banana roots by GFP-tagged strains of WT and ΔFocBik1 visualized after 7 days of inoculation. Bright-field (BF), GFP fluorescence, propidium iodide (PI) staining, and merged images are presented. Arrows indicate vascular colonization by WT