Composition of essential oil of Moroccan Dysphania ambrosioides and its antimicrobial activity against bacterial and fungal phytopathogens

This study aimed to characterize the essential oil (EO) of Dysphania ambrosioides grown in Morocco and to evaluate its antimicrobial activity against fungal ( Verticillium dahlia, Fusarium oxysporum f. sp. melonis and Fusarium culmorum ) and bacterial ( Agrobacterium tumefaciens, Pseudomonas syringae pv. tabaci, P. syringae pv. syringae and Erwinia amlovora ) phytopathogens. Essential oil was extracted using the steam distillation method in Clevenger-type apparatus and analyzed by gas chromatography-mass spectrometry (GC/MS). Its effect was studied using tests of inhibition zones in vitro and pathogenicity trials in planta . Results showed that EO of the Moroccan D. ambrosioides belongs to the ascaridole chemotype and exhibits elevated antifungal activity in vitro. When used at 500 μg ml −1 , inhibition of radial growth of Fusarium oxysporum f. sp melonis , Fusarium culmorum and Verticillium dahilae ranged from 78% to 90%, while it was extremely reduced with purified ascaridole, suggesting that its main antifungal activity relies on constituents other than ascaridole. However, EO and purified ascaridole also exhibited great potential for in vitro antibacterial activity against Pseudomonas syringae pv. syringae, Pseudomonas syringae pv. tabaci, Erwina amylovora and moderate activity against Agrobacterium tumefaciens . Furthermore, pathogenicity trials in planta revealed that EO provided elevated protection against wild fire disease caused by Pseudomonas syringae pv. tabaci on Nicotiana benthamiana when used at 100 μg ml −1 . It also protected Solanum lycopersicum plants against crown gall disease, however higher concentrations were needed. These results suggest that the EO from D. ambrosioides can be used as an antimicrobial agent to protect crops against fungal and bacterial disease.