Cylindrocarpon destructans/Ilyonectria radicicola-species complex: Causative agent of ginseng root-rot disease and rusty symptoms

Cylindrocarpon destructans/Ilyonectria radicicola is thought to cause both rusty symptom and root-rot disease of American and Korean ginseng. Root-rot disease poses a more serious threat to ginseng roots than rusty symptoms, which we argue result from the plant defense response to pathogen attack. Therefore, strains causing rotten root are characterized as more aggressive than strains causing rusty symptoms. In this review, we state 1- the molecular evidence indicating that the root-rot causing strains are genetically distinct considering them as a separate species of Ilyonectria, namely I. mors-panacis and 2- the physiological and biochemical differences between the weakly and highly aggressive species as well as those between rusty and rotten ginseng plants. Eventually, we postulated that rusty symptom occurs on ginseng roots due to incompatible interactions with the weakly aggressive species of Ilyonectria, by the established iron-phenolic compound complexes while root-rot is developed by I. mors-panacis infection due to the production of high quantities of hydrolytic and oxidative fungal enzymes which destroy the plant defensive barriers, in parallel with the pathogen growth stimulation by utilizing the available iron. Furthermore, we highlight future areas for study that will help elucidate the complete mechanism of root-rot disease development.