Etude des pouvoirs antimicrobiens et pharmacologiques des extraits de Thymus vulgaris L. et l’induction de la défense chez la tomate vis-à-vis de Fusarium oxysporum, Botrytis cinerea, et Phytophtora parasitica.

Abstract

The present work aims to study the effectiveness of Thymus vulgaris extract; a native medicinal and aromatic plant to the fight diseases of plants and inducing natural defense powers. The in vitro studied by direct contact with isolates showed total inhibition of mycelial growth and sporulation. In vivo, preventive treatment on seed and seedlings of tomato are made by applying thyme extracts an few isolates responsible for foliar and soil-borne fungal disease, the results show a very significant antifungal potency, no disease observed in studied pathtests FOL/Solanum lycopercisi and Botrytis cenirea/Solanum lycopercisi. The elicitor power of the hydroalcoholic extract is explored through the analysis of gene expression by qRT-PCR, the protein extracts and phenolic profile of tomato plants treated. The results of these experiments show clearly, induction of expression of the gene encoding the protein PR1P6 for more than 200 times and the gene encoding chitinase4 for more than 50 again. However, the synthesis of PR- proteins, no difference is observed on SDS-PAGE comparing with the control. However, the induction of the synthesis of PR1P6 protein is accomplished, is what was revealed by Western blot. In parallel, the HPLC-DAD analysis shows that this is the thyme of thymol chemotype, and its extract is rich an free and glycosylated flavonoids. Moreover, the result reveals the presence of salicylic acid known in the SAR signal and as an inducer of defense genes. Based on these results, we can confirm the effectiveness of extracts of thyme as a biopesticide with botanical origin, wealth of natural extracts with bioactive molecules and the presence of AS among the constituents of extracts of thyme entrusted the significant efficiency by direct contact and in the induction of plant defense. On the other hand, prospective evaluation of the potential toxicity of repeated doses of extracts of thyme, is studied in Wistar rats by means of clinical chemistry, histopathology and via a metabonomics approach based on 1H-NMR spectrometry. Histopathologically, no sign of abnormality or degeneration was observed in treated rats. As against the metabonomics analysis showed alterations of some metabolites involved in the energy metabolism of the mitochondria of hepatocytes. However, the magnitude of adverse effects generated after injection of repeated doses of the essential oil of thyme is much lower compared to treatments applied by the polyphenolic extract.