METHOD: Both Leaf Disc Bioassay and Visual Examination CONDITIONS: Green House - 16-24C, March-May 1987 METHOD NARR: Seedlings were transplanted into pots containing V. dahliae inoculum using an 'inoculum sandwich' technique. The plants were observed for symptoms for up to 6 weeks after inoculation. Acetone precipitates of the crude toxin of the V. dahliae isolates were prepared. The reaction of clones to the toxin was evaluated using an excised leaf bioassay. Leaves of 4-6 week old plants were excised and maintained in SDW. The intercellular spaces of the tissue between the prominent lateral veins were injected with the toxin. The disks were evaluated after 72 hours. RESULTS NARR: A 0-7 scale was used to evaluate the symptoms observed in the plants with 0 = no symptoms and 7 = plant totally wilted. For the leaf bioassay a 0-4 scale was used where 0 = no chlorosis or necrosis, 1 = chlorosis of the injected area, 2 = chlorosis and isolated necrotic spots in the injected area, 3 = necrotic areas partly coalescing, 4 = necrosis of all the injected areas and yellowing of the adjoining tissue. AUTHOR EXPLANATION: The results do not support the use of toxin as a screening tool for wilt resistance. There was a highly significant correlation between the level of wilt susceptibility and the degree of colonization by V. dahliae.