Potato tubers were subjected to cobalt-60 gamma-ray irradiation and stored at room temperature for from 10 days to 4 months. Effects of this irradiation on metabolic changes in potato tubers in response to cutting were investigated. The quantities of polyphenols, such as chlorogenic acid and isochlorogenic acid, in the tissue increased as compared with the non-irradiated sample. Although the polyphenol content and activities ofo-diphenol oxidase, peroxidase and phenylalanine ammonialyase increased after cutting, increases were lower in the irradiated sample. On the other hand, in the dose range between 5,000 and 12,400 rad, the irradiated sample showed a larger defense action against infection by the black rot fungus,Ceratocystis fimbriatathan did the non-irradiated sample.
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