Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, U.K.
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Accepted 25 March 1998.
A monoclonal antibody, OX-CH1, was raised against surface washings of Cladosporium herbarum. This antibody recognizes an epitope that is found in various fungi belonging to the genus Cladosporium, including C. fulvum, the causal agent of tomato leaf mold. The epitope is present at comparable levels in two different races of C. fulvum and in transgenic isolates derived from them. The epitope is heat- and protease-resistant but sensitive to oxidation with periodate and it is constitutively expressed in C. fulvum grown in pure culture and on the plant. C. fulvum can be detected in infected tissues at levels starting from around 1 mg fresh weight of fungus per g fresh weight of leaf tissue. Noninfected tomato leaves do not cross-react with OX-CH1. We have developed an enzyme-linked immunosorbent assay (ELISA) for fungal biomass in tomato leaves and compared it with the assay based on measurements of β-glucuronidase (GUS) activity in tissues infected with a transgenic isolate of C. fulvum race 4 carrying a uidA gene; the two assays give similar results.
© 1998 The American Phytopathological Society