Caractérisation directe deRhizoctonia solani Kühn AG3 à partir de sclérotes sur tubercules de pomme de terre par deux méthodes sérologiques

Résumé Les antisérums sont obtenus en immunisant deux lapins par voie intraveineuse avec des antigènes purifiés par chromatographie d'échange d'ions. On utilise deux préparations d'extraits mycéliens: normale et chauffée. La spécificité des anticorps obtenus est appréciée sur différentes souches deRhizoctonia. Deux techniques sérologiques sont utilisées: immunodiffusion et ELISA indirect. Les deux immunsérums obtenus présentent la même spécificité vis-à-vis du groupe AG3. Les deux techniques permettent la reconnaissance du groupe AG3 à partir des sclérotes formés sur tubercules.

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Summary Total mycelial extract ofR. solani AG3 was purified by ion-exchange chromatography. Beforehand part of the extract was heat-treated at 60°C for 10 min (Ch) and the rest left untreated (N). Results of the chromatographic analysis are given in Fig. 3. Electrophoretic analysis of the peak fractions is shown in Fig. 2. Peak C was chosen as antigen for the preparation of the two antisera by intravenous injections in two rabbits. Antibodies obtained were titrated in both cases by immunodiffusion and in indirect ELISA (Fig. 4). Specificity was examined by immunodiffusion and ELISA on heat-treated extracts of reference strains listed in Table 1. Similar results were obtained for the two antisera which were both specific to AG3 (Fig. 1 and Table 2). Characterisation tests were done by the two methods directly on sclerotia of tubers of different cultivars and origins harvested in 1991 (Table 3). The purified antigens appeared to be of a complex nature (peptides-polysaccharides) and were very immunogenic. Antibodies raised against them were sufficiently specific as to allow the identification ofR. solani AG3 sclerotica on tubers.