Óleos essenciais no controle da pinta bacteriana e na ativação de respostas bioquímicas em tomateiro

Abstract

The aim of this study was to evaluate the effect of essential oils (EOs) of Cymbopogon sp. (Citronella - CI) and Cymbopogon citratus (Lemon grass- CL) in reducing bacterial speck (Pseudomonas syringae pv. tomato - Pst.) and activation of some biochemical defense responses in tomato plants. A test was performed in vitro to assess the presence or absence of Pst inhibition halo by Eos; an experiment was carried out in vivo to evaluate the best concentration of these two oils to control bacterial speck, and another experiment was conducted to evaluate the potential of these oils and acibenzolar-S-methyl (ASM) in the activation of some biochemical responses in the tomato plant (cv. Santa Cruz). Inhibition halos were observed for EOs of CI and CL from the concentration of 1%. Essential oils of CI at a concentration of 2,000 µL L-1 and CL at a concentration of 1,500 µL L-1, as well as ASM at 0.2 g L-1, were effective in controlling bacterial speck when applied once at seven days before pathogen inoculation. CI essential oil and ASM provided partial protection capacity in tomato plants challenged with Pst. In addition, the oils and ASM promoted an increase in the total amount of phenol and cell wall lignification. Therefore, this study demonstrated the potential use of EOs in controlling tomato bacterial speck, evidencing resistance induction as the main active mode of action.