بررسي تغييرات كمي و كيفي فعاليت آنزيم پراكسيداز در تعامل بين نماتد مولد گره ريشه Meloidogyne javanica و قارچ عامل پژمردگي آوندي گوجه فرنگي Fusarium oxysporum f.sp. lycopersici

A Study of Changes in Peroxidase Activity in Interaction Between Root-knot Nematode (Meloidogynejavanica) and Tomato Fusarium Wilt Agent (Fusarium oxysporum f.sp. lycopersici)

Guaiacol - peroxidase (POX) activity was assessed spectrophotometrically in tomato(Roma VF : resistant to Fusarium oxysporum f.sp. lycopersici and susceptible to Meloidogyne javanica) roots inoculated with nematode or fungus alone, and in fungus inoculated roots preinoculated with nematode in four biological life stages of the nematode. Results showed that POX specific activity increased in plants inoculated with fungus reaching its maximum level at the 5th day while in nematode inoculated plants the activity of the enzyme increased only until the second day and then decreased. POX enzyme activity showed a significant decrease in treatments (nematode + fungi) as compared with the fungi inoculated control plants. Results showed that the nematode is able to change or suppress induction of this enzyme even against fungi. Nematode in all its biological stages can suppress the induction of POX activity in tomato roots, but in young adult formation stage the suppression is more pronounced than in the other life stages of the nematode including giant cell formation, egg-laying and penetration. Native polyacrylamide gel revealed the presence of five isozymes of POX with relative mobility (Rm) values of 0.30, 0.40, 0.50, 0.51 and 0.65 in root extract after a specific activity of stain inoculated with fungus. Isoforms with Rm values of 0.30, 0.40 and 0.65 showed lower intensity in fungus + nematode inoculated plants as compared to inoculation with the fungus alone. Based on the results obtained in this study, nematode infection resulted in suppression of tomato defenses, reduced tolerance or resistance to fungus(as a secondary pathogen) and resulted in an intensification of the fungal disease.