Induce resistance against bacterial speck disease of tomato Pseudomonas syringae pv. tomato by the chemical inducer β-aminobutyric acid

The ability of beta-aminobutyric acid to induce resistance tomato (Lycopersicon esculentum Mill. var. GS12) seedlings against bacterial speck disease was studied. Different concentrations were used as: 100, 200, 300, 400, 500, 600 mg/lafter tomato plants were sprayed with 10(8) CFU/ml foliar Pseudomonas syringae pv. tomato suspension. The results revealed that the concentration of 100 mg/l of beta-aminobutyric acid was the most efficient in reducing disease incidence and severity, furthermore it was found that all used concentrations improved tomato seedlings growth compared with control. The response of the treated tomato seedlings to the different concentration of beta-aminobutyric acid to induce systemic acquired resistance against bacterial speck (P. syringae pv. tomato) was found to be correlated to fluctuations with the amount of some compounds known to interfere with the defense mechanism against pathogen invading including: free salicylic acid, ethylene, chitinase, peroxidase, beta-1,3- glucanase enzymes, protein content, and total phenolic compounds. The biochemical analysis indicated that tomato seedlings sprayed with 100 mg/l of B-aminobutyric acid produced highest amounts of ethylene 9 and 15 days post inoculation which was significantly different from control, while highly recovered free salicylic acid was 12 days post inoculation. The recovered level of endogenous enzymes peroxidase and beta-1.3- glucanase was increased over time post inoculation, where the highest amount was 15 days post inoculation. The highest recovered chitinase was 9 days post inoculation and protein compounds contents were increased gradually over time and the highest amount were 12 days post inoculation, in which, it was found that was significantly different compared with control. These results were correlated with low level of disease incidence and severity compared with control and with the high recovered population of P. syringae pv. tomato of 5.38*10(8)CFU /ml after 21 days of inoculation. The results revealed that there is no correlation between total phenolic contents in tomato seedlings treated with beta-aminobutyric acid on induces systemic resistance.