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 dev eloped to determine simultaneously acibenzolar-S-methyl (CGA 245 704) and i ts acid derivative (CGA 210 007) in tomato leaves. The limit of detection a nd 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 treate d with 250 muM CGA 245 704, it was found that the inducer rapidly transloca tes 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 el apsed in both treated and untreated tomato leaves, reaching negligible valu es 72h after treatment. The acid derivative, CGA 210 007, was formed in tom ato plants as early as 2h after CGA 245 704 treatment, albeit only in the t reated leaves. CGA 210 007 residues decreased in treated tomato leaves with a trend similar to that observed for CGA 245 704. Treatment of tomato plan ts with CGA 245 704 or CGA 210 007 at 250 muM systemically protected the pl ants against Pseudomonas syringae pv tomato attacks, the causal agent of ba cterial speak disease. Evidence of this were reductions in the degree of in fection, the bacterial lesion diameter and the bacterial growth in planta. Since neither CGA 245 704 nor CGA 210 007 inhibited bacterial growth in vit ro and the protection against bacterial speak of tomato was observed when t he two compounds were completely degraded, the protection must be due to th e activation of the plant's defence mechanisms. (C) 2001 Society of Chemica l Industry.