A host-specific toxin of Rhizoctonia solani triggers superoxide dismutase (SOD) activity in rice

Changes in the activity of superoxide dismutase (SOD) in rice in response to treatment with Rhizoctonia solani toxin and/or R. solani elicitor were studied. Treatment of rice leaf sheaths with R. solani-toxin significantly increased the SOD activity within 12 h and the maximum enzyme activity was detected 36 h after treatment at which period a fourfold increase in SOD activity was recorded compared to control plants. Isozyme analysis indicated that five new SOD isozymes (SOD-1, SOD-3, SOD-6, SOD-7 and SOD-8) were induced in rice 1-2 days after toxin treatment. In elicitor-treated rice leaf sheaths, SOD-2 increased in activity 1-5 days after treatment. Pretreatment of rice leaf sheaths with elicitor suppressed the toxin-induced accumulation of SOD.