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Peroxidase Activity in the Developing Cotton Boll and Its Relation to Decay by Diplodia gossypina. Sy-ying C. Wang, Formerly Postdoctoral Fellow, Louisiana Agricultural Experiment Station, Baton Rouge 70803, Present address of senior author: Sugar Experiment Station, Tainan, Taiwan; J. A. Pinckard, Professor, Louisiana Agricultural Experiment Station, Baton Rouge 70803. Phytopathology 63:1095-1099. Accepted for publication 15 February 1973. DOI: 10.1094/Phyto-63-1095.

Extracts of healthy carpel tissues of cotton bolls contained weak polyphenol oxidase activity and a very active peroxidase. A predominant increase in activity of peroxidase over polyphenol oxidase was noted if the carpel tissues of the bolls were invaded by Diplodia gossypina. Electrophoresis of peroxidase preparations showed that a single form of peroxidase was present in healthy bolls of various ages and cultivars; however, two additional bands of peroxidase activity with different intensities were detected on gels of preparations from Diplodia-infected cotton bolls. A similar pattern, of multiple bands of peroxidase activity, was found on gels of preparations from carpel tissue of bolls infected by Phytophthora parasitica, Colletotrichum gossypii, and Rhizoctonia solani. The additional multiple forms of peroxidase in diseased tissues were the result of host response. Quantitative analyses of phenol content, reducing sugars, and peroxidase activity of healthy and Diplodia-infected cotton bolls of various ages, indicate that resistant ages of cotton bolls were more related to peroxidase activity than to levels of phenol content or reducing sugars in the carpel tissues.

Additional keywords: cotton boll rot, disease resistance.