GROWTH INHIBITION OF CLAVIBACTER MICHIGANENSIS subsp MICHIGANENSIS AND PSEUDOMONAS SYRINGAE pv TOMATO BY OLIVE MILL WASTEWATERS AND CITRIC ACID
Effects of citric acid and olive mill wastewaters on the growth of seed-borne bacterial pathogens of tomato, Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato were investigated. Bacteria were exposed to citric acid (0.1 mol l-1) and 10 fold-diluted filter-sterilized olive mill wastewaters and their growth was determined by the plate count method. Citric acid inhibited the growth of both bacteria. The minimum inhibitory concentration (MICs) of citric acid, determined by the broth dilution method ranged between 1.56 to 3.13 mmol l-1 for C. m. michiganensis, and was 1.56 mmol l-1 for P.s. tomato. Olive mill wastewaters inhibited the growth of both bacteria in most experiments. In some, however, a slight growth or reduction in size of the colonies of C. m. michiganensis was observed. Neither treatment showed negative effects on seed germination. Results of this study suggest that citric acid at 0.1 mol l-1 concentration can prove useful for the elimination of both pathogens from tomato seeds.