Effect of Thymus vulgaris essential oil on soybeans seeds infected with Pseudomonas syringae

Pseudomonas savastanoi pv glycinea is responsible for bacterial blight in soybean. The control of this phytopathogen usually involves the use of toxic pesticides for the environment that quickly generates bacterial resistance. As an alternative, the application of eco-friendly products such as essential oils (EO) from aromatic plants with antimicrobial activity is being assayed. The aim of this work was to carry out a preliminary study of the antimicrobial activity of Thymus vulgaris EO (TEO) on soybean seeds infected with P. savastanoi pv. glycinea B076 and Pseudomonas syringae M7-C1 in a greenhouse scale. Firstly, the non-phytotoxic concentration of TEO on seeds was determined and then the antimicrobial activity at this concentration on soybean seeds infected with both strains was analyzed. The determinations for this were: germination, plant growth, incidence, severity and effect of EO on the soil microbiome. The non-phytotoxic concentration of TEO was 1.76 mg/ml, the germination of the treated seeds was 73%, whereas for the infected seeds it was only 55 and 49%. Bacteria counts in seeds dropped 6 logs when treated with TEO. The growth parameters of the plants were similar in all treatments. The soil microbiome was not affected by EO. The incidence and severity of the disease were significantly lower in the plants that received the seed treatment with TEO.