Abstract: In this study, Fusarium oxysporum f. sp. cucumerinum was treated with 50 mg·mL^-1 of parsley seed acetone, ethanol, and distilled water extracts to study the inhibitory effect of these extracts on the colony growth of F. oxysporum f. sp. cucumerinum and the changes of the pathogen’s pathogenicity after treated with these extracts. As compared with the control, both acetone and ethanol extracts had significant inhibitory effect on the colony growth of consecutive five generations F. oxysporum f. sp. cucumerinum, and the distilled water extract had significant inhibitory effect on the growth of 1st to 3rd generations but less effect on the 4th and 5th generations. Each generation of the treated F. oxysporum f. sp. cucumerinum was inoculated on cucumber seedlings to determine the pathogen’s pathogenicity. After 7 days of inoculation, the disease index of acetone, ethanol, and distilled water extracts decreased from 26.7%, 20.8%, and 22.5% for the 1st generation to 17.5%, 3.3%, and 18.3% for the 5th generation, respectively. As compared with the control, the acetone, ethanol, and distilled water extracts had lower disease index, with a significant difference between the ethanol extract and the control. Inoculated to the 5th generation, the disease index of ethanol extract was 3.3%, with the greatest attenuation of virulence. It was suggested that parsley seed extracts could not only inhibit the colony growth of F. oxysporum f. sp. cucumerinum, but also attenuate the virulence of the pathogen. Through the consecutive treatment of the extracts, the attenuated strains for F. oxysporum f. sp. cucumerinum were obtained.

Key words: Acid rain, Wetland, Water pollution, Nutrients