USE OF MONOCLONAL-ANTIBODIES TO DETERMINE BIOMASS OF CLADOSPORIUM-FULVUM IN INFECTED TOMATO LEAVES

A monoclonal antibody, OX-CH1, was raised against surface washings of Cladosporium herbarum. This antibody recognizes an epitope that is fou nd in various fungi belonging to the genus Cladosporium, including C. fulvum, the causal agent of tomato leaf mold. The epitope is present a t comparable levels in two different races of C, fulvum and in transge nic isolates derived from them. The epitope is heat-and protease-resis tant but sensitive to oxidation with periodate and it is constitutivel y expressed in C. fulvum grown in pure culture and on the plant. C. fu lvum can be detected in infected tissues at levels starting from aroun d 1 mg fresh weight of fungus per g fresh weight of leaf tissue. Nonin fected tomato leaves do not cross-react with OX-CH1, We have developed an enzyme-linked immunosorbent assay (ELISA) for fungal biomass in to mato leaves and compared it with the assay based on measurements of P- glucuronidase (GUS) activity in tissues infected with a transgenic iso late of C. fulvum race 4 carrying a uidA gene; the two assays give sim ilar results.