Quantitative changes in superoxide dismutase, catalase and peroxidase with reference to resistance in tomato to Meloidogyne incognita

Investigations were carried out to establish a link between the activities of superoxide dismutase (SOD), peroxidase (PO), catalase and accumulation of superoxide radicals (O₂⁰) in tomato- Meloidogyne incognita interactions. Time course studies on SOD revealed that the activity of the enzyme was of lower magnitude as compared to the healthy counterpart during entire post infectional period in the resistant cultivar. There was a corresponding increase in the production of superoxide radicals in the nematode inoculated resistant host. These observations were suggestive of the fact that in resistant host, nematode infection leads to inactivation of SOD which results in production of O₂, consequently affecting the biology of the invading pathogen adversely. The increase in the enzyme activity in susceptible host was found to be maximum at 72 hrs after inoculation. There was also an increase in PO activity in inoculated Pusa Ruby, a susceptible host but was of lower order as compared to resistant host. The trend of catalase activity followed the same pattern as that of SOD activity in both the cultivars.