Control of bacterial stem rot on tomato by extracellular bioactive compounds produced by Pseudomonas aeruginosa LV strain

This study evaluated the antibiotic activity and induction of resistance in plants by compounds produced by Pseudomonas aeruginosa LV strain on the control of bacterial stem rot in tomato. Compounds were extracted from the cell-free supernatant of a bacterial culture and purified. The F4A fraction was composed of two major compounds, an antibiotic and a phenazine (PCN). The first experiment evaluated the antibiotic activity of F4A, and the second one compared the ability of F4A and PCN to elicit systemic acquired resistance (SAR). In both experiments, plants were infected with Pectobacterium carotovorum subsp. carotovorum (Pcc). The minimum inhibitory concentration of F4A was 7.81 mu g mL(-1), and PCN did not inhibit bacterial growth. The results suggest that F4A has antibiotic activity. Scanning electron microscopy revealed changes in bacterial cells after 3 h treatment with F4A. F4A and PCN decreased symptoms of stem rot and increased fruit production. Plant response was estimated by determination of peroxidase, polyphenol oxidase, and phenylalanine ammonia lyase activity. Plants treated with PCN or F4A showed greater enzyme activity than plants that were not treated or treated with Bion (R), suggesting that PCN increased SAR. The compounds showed the potential to control Pcc in vitro and in vivo and to induce plant response.