Main symptoms

- Structures present in root cells

The presence of Olpidium virulentus (eg Olpidium brassicae ) in the roots can easily be confirmed by microscopic observation of the latter. This fungus, an obligate aquatic parasite, forms resting spores or chlamydospores in the cells of the cortex and sporangia which are the source of numerous zoospores (Figures 1 and 2).