Ilyonectria Root Rot of Ginseng Is Attenuated via Enzymatic Degradation of the Extracellular Fe³⁺-Bound Siderophore N,N′,N″-Triacetylfusarinine C

Ilyonectria root rot of ginseng can greatly decrease crop yields often by 20-30% at time of harvest. We previously determined that the Ilyonectria siderophore N,N ',N ''-triacetylfusarinine C (TAFC) is critical for the ginseng pathogens' virulence. TAFC enables the fungus to acquire iron from its environment, and once inside the cell, iron is typically released via enzymatic hydrolysis of TAFC's three ester moieties. This iron acquisition system has been extensively studied in Aspergillus fumigatus. Based on this system, we hypothesized that AfEstB, a well-characterized TAFC esterase produced by A. fumigatus, could be used for siderophore-targeted biocontrol of Ilyonectria. Application of purified recombinant AfEstB to ginseng roots inoculated with virulent I. mors-panacis demonstrated a significant protective effect, which disappeared when AfEstB was no longer applied. These data support the targeting of Ilyonectria iron acquisition mechanisms though enzymatic degradation of TAFC as an effective means of controlling Ilyonectria root rot of ginseng.