Emulsão de óleo essencial de alecrim-do-campo (baccharis dracunculifolia) no controle de doenças e indução de resistência em tomateiro

Abstract

Essential oils (EO) correspond to several volatile plant compounds that can influence the biological activities of different organisms. Alecrim-do-campo (Baccharis dracunculifolia D. C.) is known for the therapeutic use of green-propolis, however little is known about the potential of the EO of this species in the control of plant diseases. This work aimed to evaluate the potential of Baccharis dracunculifolia (Bd) EO emulsion in the in vitro and in vivo control of Septoria lycopersici (Sl) and Xanthomonas vesicatoria (Xv) that cause diseases in tomato (Solanum lycopersicum). In vitro assays were prepared from the initial emulsion (100%) at a concentration of 300 μl/mL. Ten concentrations were tested (0; 0.1; 0.5; 1.0; 1.5; 2.0; 2.5; 3.0; 4.0; 5.0%) with 4 replications each. For Sl, spore germination (Ge) and mycelial growth (Cm) were evaluated. For Xv, the concentration of bacterial suspension (Csb) in liquid culture medium was evaluated. Three in vivo assays were performed on tomato plants (cv. Santa Clara I-5300) to assess septoria severity, bacterial spot severity and biochemical assessment of the induction of plant defense enzymes peroxidases (Pro), polyphenoloxidases (Plo) and total soluble Protein (Pst) content, being 5 treatments (0; 1.0; 4.0; 7.0; 10.0%) with 5 replicates each and 2 plants per replicate. Results were expressed in mg protein.g tissue-1 for Pst and Δ abs. min-1mg protein-1 for Pro and Plo. For in vitro conditions, a reduction in the germination percentage and mycelial growth of Sl and total inhibition of Xv from 1.5% was observed. There was a significant increase in Pst up to 4%, and an increase in the activity of Pro and Plo enzymes up to the maximum concentration (10%) without phytotoxicity damage to plants at doses higher than those necessary to control the development of pathogens in vitro. There was no statistical difference in the evaluations of septoria and bacterial spot severity. Thus, it can be considered that the use of Bd essential oil emulsion for the control of Sl and Xv and the increase of enzymatic activity in the production of molecules that act in the protection of the plant as chemical and physical barriers (quinones, tannins and lignification) showed satisfactory results.