Persistence and translocation of a benzothiadiazole derivative in tomato plants in relation to systemic acquired resistance against Pseudomonas syringae pv tomato

A reproducible and accurate procedure, based on HPLC analysis, has been developed to determine simultaneously acibenzolar-S-methyl (CGA 245 704) and its acid derivative (CGA 210 007) in tomato leaves. The limit of detection and quantification of the method are 0.015 and 0.15mg litre(-1) for CGA 245 704 and 0.030 and 0.30mg litre(-1) for CGA 210 007. In tomato plants treated with 250 muM CGA 245 704, it was found that the inducer rapidly translocates fi om treated leaves (cotyledons, Ist and 2nd) to untreated Leaves (3rd to 5th), with the maximum translocation (40% of the total quantity found) occurring 8h after the treatment. CGA 245 704 residues decreased as time elapsed in both treated and untreated tomato leaves, reaching negligible values 72h after treatment. The acid derivative, CGA 210 007, was formed in tomato plants as early as 2h after CGA 245 704 treatment, albeit only in the treated leaves. CGA 210 007 residues decreased in treated tomato leaves with a trend similar to that observed for CGA 245 704. Treatment of tomato plants with CGA 245 704 or CGA 210 007 at 250 muM systemically protected the plants against Pseudomonas syringae pv tomato attacks, the causal agent of bacterial speak disease. Evidence of this were reductions in the degree of infection, the bacterial lesion diameter and the bacterial growth in planta. Since neither CGA 245 704 nor CGA 210 007 inhibited bacterial growth in vitro and the protection against bacterial speak of tomato was observed when the two compounds were completely degraded, the protection must be due to the activation of the plant's defence mechanisms. (C) 2001 Society of Chemical Industry.