Infection of cotton seedlings with Verticillium dahliae . A: Aseptic growth in tissue culture flask. B: status at 3 dpi for roots treated with conidial suspension. C: Infection process, based on GFP-tagged V. dahliae strain. D: Vascular tissue of uninfected hypocotyl section (CK). Severe browning of vascular tissue in longitudinal section at 7 dpi. E: Mycelia growth in vascular tissue of surface-sterilized hypocotyl section prepared from cotton seedling at 2 dpi, then incubated for 3 d on 25% potato dextrose agar. F: Mycelium observed with optic microscope.