Inhibition of H2O2-degrading enzymes in the response of Mi-bearing tomato to root-knot nematodes and salicylic acid tratment

S. Molinari

Abstract


Near-isogenic lines of tomato, resistant and susceptible to root-knot nematodes, were inoculated with (a)virulent Meloidogyne incognita juveniles and treated with the defense reaction elicitor salicylic acid. Catalase activity was significantly inhibited in resistant roots by either nematode infestation or salicylic acid treatment. Such inhibition did not occur in susceptible roots and in resistant roots inoculated with a virulent isolate of M. incognita. The H202-degrading activities of catalase and ascorbate peroxidase were both inhibited in the upper green tissues of the resistant seedlings 24 hours after nematode inoculation, although, they were restored or enhanced compared with those of controls 48 h after inoculation. Resistant seedlings incubated overnight in salicylic acid showed a marked inhibition of catalase activity in green tissues whilst such inhibition was much less consistent with susceptible seedlings.

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