Inhibitory effect of l-methionine on bacterial speck of tomato

l-Methionine (L-Met) is an amino acid necessary for protein biosynthesis. In this study of the inhibitory effect of L-Met on bacterial speck of tomato (Pseudomonas syringae pv. tomato: PST), leaves of tomato plants were pretreated with L-Met, then inoculated with PST. Symptoms were less severe compared with the control, bacterial populations in inoculated leaves of L-Met-treated plants were lower than in inoculated leaves of the untreated. Quantifying the expression of PR1b, a marker gene for the salicylic acid (SA) signaling pathway, in L-Met-treated plants after PST inoculation showed that PR1b expression was greater than in the untreated plants. These observations suggest that the inhibitory effect of L-Met treatment on bacterial speck of tomato may be due to priming of the SA-related signaling pathway.