Figure 2

Pathogen structures identified in longitudinal root sections. A, Root cortical tissue. Several structures can be identified, such as primary hyphae (1), botryose hyphae (2), and survival structures such as chlamydospores (3). B, Hyphae observed at high magnification (x1000) (arrowhead). The pathogen penetrates the host cell through the cellulose wall. Accumulation of well stained cell wall material (4) (possibly papillae) is observed surrounding the penetration hyphae (5). C, Invasion of the central cylinder parechymatic tissue of the root by the pathogen 14 days after inoculation. Botryose hyphae that grow haphazardly were found inside the cells (arrowheads). At this time, we found immature or small chlamydospores in the parenchymatous cells (6). D, Several hyphae (1) and structures resembling finger-like haustoria (7) in cortical cells.