Thirteen Plantago lanceolata (buckhorn plantain) and 13 Rumex crispus (curly dock) plants were grown from seed in 0.5-
liter pots. Nine plants of both species were needle inoculated at the base of one leaf in each rosette with a 5-day-old culture of E.tracheiphila by the same needle inoculation technique described previously. Four plants of each species were wounded at the same location with a sterile needle as negative controls. Three weeks after inoculation,leaves and stems were harvested,surface sterilized, and ground in 2ml of ELISA sample buffer in mortar and pestles. Two hundred microliters of each of the ground, inoculated, plant samples was immediately pipetted into eight ELISA plate wells coated overnight at 4°C with a 1:100 dilution of anti-E. tracheiphila antibodies (one ELISA plate for each of the two species). Each of the four homogenized control samples of both species was pipetted into duplicate wells in the appropriate ELISA plate. A culture of E. tracheiphila grown on NAP and suspended in 10 ml of sample buffer was pipetted into eight wells of each plate as positive controls.Eight wells were filled with buffer as negative controls. The last eight wells of each plate were filled with equal parts of the suspended E. tracheiphila culture and the homogenized control plants of the appropriate plant species. This was to ensure that the curly dock and buckhorn plantain plant homogenates did not kill the bacteria during isolation. The samples were incubated in the antibody-coated ELISA plates for 1 h at room temperature and then rinsed
three times with PBS. All of the wells were then filled with 200 μl of NBP and incubated at room temperature for 5 days.
The contents of each well were streaked for isolation on NAP. After 5 days of incubation at room temperature the resulting
colonies with colony morphology resembling that of E. tracheiphila were tested with DAS-ELISA and needle inoculated
into cucumber seedlings to verify pathogenicity.