Two strains of growth promoting rhizobacteria (PGPR), Pseudomonas putida MG4, and Pseudomonas fluorescens MG18 selected as inducers of systemic resistance, were tested for biological control of leaf spot caused by Alternaria solani and bacterial speck caused by Pseudomonas syringae in tomato. The two bacterial isolates afforded reduced disease intensity and elicited systemic protection against the two studied pathogens. The two PGPR stimulated a systemic response in tomato by inducing high rates of enzyme activity of phenylalanine ammonialyase (PAL), peroxidase (PO), polyphenol oxidase (PPO) and chitinase as well as the accumulation of high level of phenolics. The combined effect of these factors induced drastic decrease in the degree of infection of the two pathogens.
Key words: Tomato, systemic resistance, PAL, PO, PPO, Chitinase, phenolic compounds, biological control