Fig. 3.

Illustration of ginseng root infection by the highly aggressive Ilyonectria species, I. mors-panacis, and other weakly aggressive Ilyonectria species, leading to the occurrence of rotting and rusty symptoms, respectively. I. mors-panacis produces large amounts of cellulases and pectinases, and the plant rapidly responds to invasion by the production of phenolic compounds. However, the pathogen suppresses the toxicity of the phenolic compounds by producing polyphenol oxidases. In parallel, the pathogen sequesters plant and rhizospheric iron by producing siderophores. The other Ilyonectria species cannot penetrate the host plant as rapidly as I. mors-panacis because they produce lower amounts of hydrolytic and oxidative enzymes. The plant is therefore able to successfully retard their invasion. Iron exists on the root surface and within the plant cells and binds to the accumulated phenolic compounds, forming complexes that are likely responsible for the rusty coloration.