Fig. 4

Laser confocal microscopic images of F. graminearum infection of wheat coleoptiles at 24 hpi. Tissue cells of wheat coleoptiles were stained with PI (Propidium iodide) (red). a, b Cell-to-cell invasion using constricted invasive hyphae pegs (about 1 μm). This image is a three-dimensional projection of 27 optical sections acquired with a z-interval of 0.35 μm. c, d Tissue cells of wheat coleoptiles were visible even after extensive proliferation of F. graminearum inside them. Contents of the infected cells are not disintegrated. PI staining identifies a few dead invasive hyphae (arrows) in the infected wheat coleoptiles cells at 24 hpi. This image is a three-dimensional projection of 55 optical sections acquired with a z-interval of 0.15 μm. e A proposed model depicting the early stages (16–36 hpi) of F. graminearum proliferation inside wheat coleoptiles