Acibenzolar-S-methyl induces lettuce resistance against Xanthomonas campestris pv. vitians

Acibenzolar-S-methyl (Benzo [1,2,3] thiadiazole-7-carbothioic acid-S-methyl ester, ASM; Bion 50 WG) was found to be more protective for lettuce against bacterial speck disease caused by Xanthomonas campestris pv. vitians. The experiments were conducted under controlled climatic conditions in the greenhouse, and induction of defense mechanism using ASM treatment against challenged inoculation with X. campestris pv. vitians was studied. It was effective in reducing the severity of disease and bacterial growth when compared with control and copper hydroxide. Pathogen growth was also followed with specific PCR before the typical symptom development on leaf tissues. Equal plant tissues collected from infected pnjm, lants were used in order to compare different treatments and pathogen invasion. The induction interval (48) before inoculation period was convenient for the control of pathogen by ASM treatment. The findings show that ASM treatment in inoculated plants has long lasting effect to induce defense-related enzymes, contributing to the enhancement of plant resistance. The effect was comparable with copper treatment. As a marker of resistance, PR protein activity chitinase showed remarkable increase, depending on decreasing bacterial growth in planta.