INFLUENCE OF STYLBENOIDS ON AGROBACTERIUM TUMEFACIENS

A strain of Agrobacterium tumefaciens, isolated from the trunk of infected V. vinifera L. cv. Rkatsiteli was studied microscopically and its pathogenesis was established. The goal of the research was to study the role of stilbenoids on the bacterial growth. The bacterium strain was inoculated in two ways: a) the surface of the growth medium was covered by a watery suspension of stilbenoids; b) Stilbenoids was added to the growth medium before sterilization. In both experimental protocols the concentrations of the stilbenoids were: 1 mg/100 ml, 2 mg/100 ml, 3 mg/100 ml, 4 mg/100 ml, 5mg/100ml, 10 mg /100 ml, 15mg/100ml, 20 mg /100 ml and 30 mg /100 ml. The control version was the same medium without stilbenoids. The incubation period was 14-15 days at 270C and all the treatments completely (100%) inhibited Agrobacterium tumefaciens growth over the control. A second experiment was therefore set up in order to study the bacterial growth inhibition under stilbenoid concentrations lower than 1 mg/100 ml (ranging from 0.1 mg/100 ml to 0.9 mg/100 ml): the bacterial growth inhibition increased from 0.0 % to 88.0% by increasing the stilbenoid concentrations.