Induction of enzymatic scavengers of active oxygen species in rice in response to infection by Rhizoctonia solani

Changes in the activities of peroxidase, ascorbate peroxidase, catalase and superoxide dismutase in rice in response to infection by Rhizoctonia solani were studied. A significant increase in peroxidase activity was observed in R. solani-inoculated rice leaf sheaths 1 day after inoculation and the maximum enzyme activity was recorded 3 days after inoculation at which period a 3-fold increase in peroxidase activity was observed compared to the untreated control. Three peroxidase isozymes viz., PO-4, PO-5 and PO-6 were induced in rice upon infection by R. solani. Ascorbate peroxidase and catalase activities significantly increased 1-2 days after inoculation and the maximum enzyme activities were recorded 5 days after inoculation. Superoxide dismutase activity increased significantly 2 days after inoculation and increased progressively, reaching four times the control value at 7 days after inoculation.