CHANGES OF CATALASE AND SOD ACTIVITIES IN THE EARLY RESPONSE OF TOMATO TO MELOIDOGYNE ATTACK

Abstract

Excised roots of Mi-bearing resistant tomato were inoculated with Meloidogyne spp. in agar. Variations of antioxidant enzyme activity were detected as early as 24 hours after the inoculation. Catalase activity was inhibited by the infestation. Catalase inhibition was also observed in roots 24 hours after seedlings were inoculated in pots with second-stage juveniles. The catalase inhibition was specific for resistant cultivars whilst susceptible cultivars had their catalase content enhances by root-knot nematode infestation. Superoxide dismutase activity did not show reproducible changes due to nematode infestation. Catalase inhibition is indicated as a mechanism by which hydrogen peroxide level is increased in resistant roots thus triggering a hypersensitive response and producing a chemical toxic to nematodes.