Bioherbicide cynara: weed control through natural resources for sustainable agriculture

• Autores: Daniela Firmino Rosa
• Directores de la Tesis: Francisco Antonio Macías Domínguez (codir. tes.), Rosa María Varela Montoya (codir. tes.)
• Lectura: En la Universidad de Cádiz ( España ) en 2025
• Idioma: español
• Tribunal Calificador de la Tesis: Ana Azucena González Coloma (presid.), José María González Molinillo (secret.), Aurelio Scavo (voc.)
• Programa de doctorado: Programa de Doctorado en Recursos Agroalimentarios por la Universidad de Cádiz
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• Resumen

  • Synthetic herbicides, while effective for weed control, have led to significant environmental concerns, including soil and water contamination, biodiversity loss, and the emergence of resistant weed species. In response to increasingly stringent regulatory frameworks, there is a growing demand for sustainable alternatives. Allelochemicals represent eco-friendly and biodegradable options, characterized by distinct weed suppression mechanisms. Among these, sesquiterpene lactones exhibit potent phytotoxic activity and are abundantly found in Cynara cardunculus leaves - approximately 95 g/kg dry weight, with cynaropicrin being the major compound (aproximadamente igual a 87 g/kg dry weight). Despite their potential as natural herbicides, the commercial development of bioherbicide has been limited by the high cost associated with large-scale industrial extraction and purification.

    To address this constraint, the present doctoral research focused on the development of sesquiterpene lactone-enriched C. cardunculus leaves extracts using membrane process technology - specifically diaultrafiltration - as a sustainable and efficient method for extract fractionation and concentration. This sustainable approach aimed to enhance the bioavailability and phytotoxic activity of C. cardunculus leaves extracts. The enriched fractions were evaluated for phytotoxic activity against a panel of agronomically relevant weed species, including Portulaca oleracea, demonstrating enhancement in activity. Sesquiterpene lactones putative mode of action was also investigated, having as a result the effect in total chlorophyll content and oxidative stress induction.

    Cynaropicrin, as the predominant sesquiterpene lactone in C. cardunculus leaves extract, was evaluated for its stability in different abiotic (pH and temperature) and biotic conditions (soil). These experiments provided insights into the sesquiterpene lactone behavior within agriculture contexts, determining its degradation products and its phytotoxic activity.

    A targeted formulation strategy was further developed to improve the phytotoxic activity and storage stability of the enriched extracts. A nanoemulsion-based formulation was optimized using response surface methodology (Box-Behnken design) to achieve reduced particle size and enhanced stability. Both the unformulated extract and its nanoemulsion were tested for phytotoxic activity, and nanoemulsion storage stability was evaluated. The results demonstrated a clear increase in phytotoxic activity against the studied weed species, as well as 90-day storage stability.

    This research advances sustainable weed management strategies by demonstrating the potential of C. cardunculus-derived sesquiterpene lactones as natural herbicides. It uses innovative approaches to make the final extracts more effective and stable for their future end-use in agriculture.