Oxidative Enzymes of Ceratocystis fimbriata Isolates Differing in Host Specificity

Eight isolates of Ceratocystis fimbriata differing in pathogenicity on sweet potato roots were compared in vitro for peroxidase, catalase and polyphenol oxidase activities. Pathogenic isolates were generally lower in specific activities of peroxidase and catalase than the nonpathogenic isolates. Cultures of pathogenic isolates were distinguished by black culture liquid compared to the yellow color of nonpathogenic isolates. No consistent differences among the isolates were apparent when the specific activity of polyphenol oxidase preparations were compared on various phenolic substrates. The peroxidase of C. fimbriata had an approximate molecular weight of 81,000 when compared with known protein standards on a column of Sephadex G-100 dextran gel. Its substrate specificity differed from horseradish peroxidase in that it was nonreactive with guaiacol.