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Physiology and Biochemistry

Biological Activity and Specificity of a Toxin Produced by Cladosporium fulvum. G. Lazarovits, Graduate student, Department of Botany, University of Toronto, Ontario, Canada, M5S 1A1, Present address of senior author: Agriculture Canada Research Institute, University Sub Post Office, London, Ontario, N6A 5B7; V. J. Higgins, associate professor, Department of Botany, University of Toronto, Ontario, Canada, M5S 1A1. Phytopathology 69:1056-1061. Accepted for publication 9 March 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1056.

The biological activity of a glycoprotein toxin produced in vitro by Cladosporium fulvum was studied by necrosis, callose deposition, and ion leakage assays. Concurrent appearance of callose and necrosis was not altered by the toxinís degree of purification or concentration. Increased leakage of electrolytes from toxin-treated tomato leaf tissue was concentration-dependent, and this assay proved to be the most sensitive. As judged by necrosis and callose deposition, C. fulvum toxin from races 1, 10, and 12 had similar effects on all tomato cultivars regardless of gene for resistance. Similarly, quantitative comparisons of ion leakage from different tomato cultivars treated with purified race 1 toxin failed to support an earlier report that the toxin was cultivar-specific. Nonhost plant species were unaffected by the toxin. The toxin stimulated the respiratory rates of tomato and of nonhost species tobacco and pepper.

Additional keywords: tomato leaf mold.