USE OF SPECIFIC ANTIBODIES TO A FRACTION OBTAINED BY SIZE EXCLUSION CHROMATOGRAPHY TO IMPROVE THE SEROLOGICAL CHARACTERIZATION OF RHIZOCTONIA-SOLANI KUHN AG3

A soluble mycelial extract of R. solani AG3 was purified by size exclusion chromatography. Five peaks were present in the elution profile: the first was well defined and of large volume. It was retained to immunise a female rabbit by intradermic injection. The titre of the antiserum determined by double immuno-diffusion in agarose was 0.125. The antiserum was tested on isolates of R. solani AG1, AG2, AG3, AG4, AG5, AG6, AG7, AGB1 and of Ceratobasidium CAG1, CAG2, CAG3, CAG4 and CAG5 (Table 1) using three different methods: immunodiffusion with the test material adjusted to 3 mg/ml of proteins. Only AG3 isolates formed a single precipitation line (Fig. 1). electrotransfer and immuno-blotting. Test samples containing 8 mg/ml of proteins were electrophoresed under natural conditions in a discontinuous system. The proteins were then electrotransferred to a nitrocellulose membrane. Immunoenzymatic staining showed that only one band was present in AG3 isolates (Fig. 2). immunoenzymatic labelling of the mycelium demonstrated the presence of dark granules on the cell wall of only AG3 isolates (Fig. 3). This study has shown the value of antigen purification to obtain an antiserum against specific fraction of AG3 isolates. It would appear that the antigen is a polysaccharide-protein complex.