Functional Variation of Ascorbate Peroxidase in Black Pepper (Piper nigrum) Varieties during Infection of Phytophthora capsici

Activity of ascorbate peroxidase was determined in black pepper (Piper nigrum) infected by Phytophthora capsici causing foot rot disease in varieties of Shakthi and Panniyur. The pathogen Phytophthora capsici was inoculated under in vitro conditions to the healthy plants of Shakthi and Panniyur. The black pepper plants of Shakthi variety at post inoculated phase showed a progressive increase in ascorbate peroxidase (APX) activity and the inoculated plants remain healthy without showing the symptoms of foot rot indicating the role of APX in inducing tolerance during pathogenesis. Meanwhile a gradual depletion of ascorbate peroxidase activity was observed in the inoculated plants of Panniyur, exhibiting the susceptible nature with all critical symptoms of foot rot infection. The activity of APX in both varieties was also checked qualitatively by native gel electrophoresis. Histological variations at cellular level during infection was examined by scanning electron microscope (SEM). An analytical comparison was done between the APX activity and scavenging of H2O2 in the varieties during infection.