| Abstract: | Corynebacterium wilt of tomato causes severe losses in France and Belgium. The disease can be seed-transmitted and sanitary selection of seedlots is a direct prophylactic control method. It must be selective, objective and sensitive and must provide information on the pathogenicity of the bacteria detected. A method is proposed that associates immunofluorescence (IF) staining with bioassay and isolation. In a preliminary comparison of inoculation on different host plants, tomato seedlings with two or four leaves were the most sensitive. Artificially and naturally contaminated seed extracts were IF-screened and confirmed by isolation of the pathogen from inoculated seedlings. The detection method consists of maceration of tomato seeds in PBS-cycloheximide buffer, filtration and centrifugation of the seed extract, and IF screening of the pellets with two antisera. Pellets with positive or suspect IF reading (threshold 5 × 103 cells in the pellet) are inoculated into tomato seedlings incubated at 25°C. Within 30 days the seedlings are inspected for typical wilt symptoms and isolation experiments are carried out from the vessels. The method has been tested on commercial seedlots. |
