Óleo essencial de Moringa oleifera Lam. na microbiota fitopatogênica e potencial fisiológico de sementes de Phaseolus vulgaris L.

Abstract

The use of essential oils configures itself as a promising alternative for the treatment of seeds. In this context, this work aimed to evaluate the effect of the essential oil of Moringa oleifera (EOM) on the phytopathogenic microflora and the physiological potential of bean seeds. For this, three experiments were conducted in order to extract and characterize the EOM, to evaluate its effect on viability, vigor, isoenzyme activity in bean seeds, and on plant pathogens. The extraction and characterization of EOM occurred by hydrodistillation of the leaves in Clevenger and gas chromatography-mass spectrometry. In assessing the EOM antimicrobial activity, were used six treatments, five doses of essential oil (0,0%, 0,1%, 0,2%, 0,4% and 0,8%) and a fungicide, in evaluating the germination of spores and fungi incidence percentage (blotter test). The same doses of EOM and a bactericidal were used against Xap. In turn, used seven treatments (five doses EOM, a fungicide and bactericide) with eight repetitions of fifty seeds distributed in CRD for evaluation of the percentage of germination, GSI and first count. The esterase, alcohol dehydrogenase, isocitrate lyase, and superoxide dismutase were investigated by polyacrylamide gel electrophoresis. The effects of the oil levels on germination of fungal spores, bacterial growth and physiological potential of seeds were evaluated by regression equations and the mean quantitative treatment (dose) were compared to synthetic treatment by the Dunnet test (P> 0,05). In the essential oil composition, eleven compounds were identified, of which 12.92% was terpenes (linalool, thymol and β-eudesmol) with antimicrobial properties above mentioned in the literature. The synthetic fungicide may be substituted by dose containing 0.4% EOM for the incidence of A. flavus, Fusarium sp. and Alternaria sp. in bean seeds. On germination of fungal spores, none of the OEM doses used were statistically equal to fungicidal, however, increasing doses obtained linear effect on the germination of spores of Rhizopus sp. and Fusarium sp. Despite the reduction in the number of CFUs, the EOM doses were inferior to synthetic bacterial elimination Xap. For the physiological potential, the dose with 0,8% EOM reduced the viability and vigor of the seeds of the cultivar Colibri and stood below the bactericide and fungicide for GSI and first count. For Campos Gerais, the dose with 0,8% EOM promoted germination and was superior to the bactericidal for the germination percentage and first count. The point of maximum emergence and GSI were obtained with doses of 0.6% and 0.28% (Campos Gerais), and 0,38% to 0,2% (Colibri). Low bands of expression values for EST and ADH, related to the higher germination of seeds and the greatest expression of SOD, was associated with reduction in germination