Isolamento de metabólitos de origem microbiana com ação herbicida

• Ano de defesa: 2025
• Autor(a) principal: Schmaltz, Silvana
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Engenharia Química; UFSM; Programa de Pós-Graduação em Engenharia Química; Centro de Tecnologia
• Palavras-chave em Português: Plantas daninhas; Bio-herbicidas; Biomoléculas; Weeds; Bioherbicides; Biomolecules; CNPQ::ENGENHARIAS::ENGENHARIA QUIMICA
• Link de acesso: http://repositorio.ufsm.br/handle/1/36719

As an alternative to the use of agrochemicals, several studies have been conducted to explore new modes of action and active ingredients derived from microorganisms for weed control. In this context, the present study aims to produce and apply phytotoxic biomolecules in bioassays using the phytopathogenic microorganisms Phoma dimorpha (NRRL 43879) and Fusarium fujikuroi (SO210). The bioindicator plants used were Amaranthus retroflexus (pigweed), Raphanus sativus (radish), and Triticum aestivum (wheat). The submerged cultures of the microorganisms resulted in fermented broths, which were subjected to mycelium removal and sequential vacuum filtration using 0.22 μm and 0.45 μm pore membranes to eliminate microbial cells. The resulting cell-free broths (CFB) were extracted using ethyl acetate, and the extracts were concentrated and subjected to fractionation and purification processes via column chromatography, monitored using thin-layer chromatography. The extract from P. dimorpha was separated into three fractions, of which only Fraction 1 exhibited herbicidal activity and was subsequently subjected to further purification. Among the three compounds present in this fraction, only one was purified and tested in bioassays. Fraction 1 controlled 96.25% of A. retroflexus plants in a leaf puncture bioassay when applied at a concentration of 2 mg mL⁻¹ and 96.67% when formulated with 0.1% Tween 80 and applied to the aerial parts of plants at 600 μg mL⁻¹. The purified compound (PC) was tested on radish seed germination in a substrate-based assay and applied at concentrations of 24.5 and 12.25 mg mL⁻¹, reducing germination by 80% and 26%, respectively, compared to the control (water). Additionally, seedling length was reduced by 80% and 31%, respectively. The extract obtained from F. fujikuroi resulted in a single homogeneous fraction containing one compound, which was purified via column chromatography and tested in bioassays. In 96-well plate assays, a concentration of 23 mg mL⁻¹ completely inhibited the germination of radish and wheat seeds, whereas the crude extract and CFB allowed radicle protrusion but resulted in abnormal seedlings exhibiting chlorosis and reduced growth. Mathematical models estimated that PC concentrations of 16.0 mg mL⁻¹ for radish and 0.9 mg mL⁻¹ for wheat would be sufficient to suppress germination. In substrate experiments, PC at 6.4 and 64.0 mg mL⁻¹ did not inhibit germination but caused anomalies in radish seedlings and significantly reduced wheat seedling growth. In naturally infested soil, PC maintained phytotoxic symptoms for 21 days, and after 28 days, a concentration of 64.0 mg mL⁻¹ significantly reduced radish seedling growth. The results highlight the potential of these compounds for the development of bioherbicides.