Antibacterial Metabolites from Kiwi Endophytic Fungus Fusarium tricinctum , a Potential Biocontrol Strain for Kiwi Canker Disease.

Pseudomonas syringae pv. actinidiae (Psa) is a Gram-negative bacterium causing the kiwifruit canker disease, resulting in serious economic losses to the kiwifruit industry. This study investigated the use of an endophytic fungus, Fusarium tricinctum , obtained from the kiwi plant ( Actinidia chinesis ) as a potential biocontrol strain against the Psa. F. tricinctum showed an inhibition rate of 59.5% in vitro against Psa. Bioassay-guided isolation was conducted on the cultural broth of F. tricinctum and seven new imidazole alkaloids, (±)-fusaritricine J ((±)- 1 ) and fusaritricines K-P ( 2 - 7 ), and four enniatins ( 8 - 11 ) were identified. Their absolute configurations were established through extensive spectroscopic methods, quantum chemical calculations, and X-ray single crystal diffraction. Compounds 1 , 4 , 5 , and 8 - 11 showed comparable anti-bacterial activities against Psa as positive control, with MIC values of 25-50 μg/mL. Further cell membrane permeability assay suggested that the most active compound 4 could destroy the bacterial cell wall structure. Hence, F. tricinctum metabolites could be applied as potential anti-Psa agents, and F. tricinctum could be considered a biocontrol strain for the control of the kiwifruit canker disease.