Peroxidase and 6-Phosphogluconate Dehydrogenase in Resistant and Susceptible Cotton Infected by Meloidogyne incognita

  • Gregory R. Noel
  • Michael A. McClure


Assays of specific activities and electrophoretic separations of multiple forms of 6-phosphogluconate dehydrogenase and peroxidase in cotton resistant and susceptible to Meloidogyne incognita were conducted 6 days after inoculation. Specific activities were greater in infected than in uninfected roots and also were greater in the resistant cultivar, 'Clevewilt 6-3-5,' than in the susceptible culti.var, 'M8.' In uninfected roots, peroxidase activity was greater in Clevewilt roots than in M8 roots, but activity of 6-phosphoglueonate dehydrogenase was the same. Multiple forms of peroxidase and 6-phosphogluconate dehydrogenase were separated and resolved by polyacrylamide gel electrophoresis. These experiments demonstrated the occurrence of altered metabolism upon infection and differences in enzyme activity between resistant and susceptible cultivars. Key Words: Resistance, root-knot nematode, biochemistry, multiple forms, specific activity.