Peroxidase and 6-phosphogluconate dehydrogenase in resistant and susceptible cotton infected by Meloidogyne incognita.

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.