Allelopathic effects of Cynara cardunculus L. extracts

Abstract

The present doctoral thesis aims to explore the potential use of Cynara cardunculus L. leaf extracts for the biological control of weeds and pathogen microorganisms. In a first trial, the allelopathic effects of its leaf aqueous extracts on seed germination of six common weeds was demonstrated. Secondly, the set-up of the most efficient extraction method of its allelochemicals in terms of costs, yields and inhibitory activity was realized, selecting dried leaves as the best plant material and ethanol and ethyl acetate as the best solvents. Moreover, new C. cardunculus allelochemicals (cynaratriol, desacylcynaropicrin, 11,13-dihydro-desacylcynaropicrin and pinoresinol) were purified. Third, the effect of genotype, harvest time and light stress on the phytotoxicity, quantity and composition of sesquiterpene lactones in C. cardunculus leaf extracts was evaluated through a new UHPLC-MS/MS analysis method. Wild and cultivated cardoon showed the highest concentrations, while the April harvest revealed the best harvest time. Moreover, light stress stimulated the production of these allelochemicals. In a second trial, the effects resulting from three consecutive years of cultivation, in two different areas, with globe artichoke, cultivated and wild cardoon on the quali/quantitative weed soil seed bank and the changes in the eubacterial communities were studied. In both areas, C. cardunculus reduced weed seed bank in all treatments compared to controls. Nevertheless, the presence of cultivated cardoon had a negative influence towards Bacillus subtilis and a positive one on Pseudomonas putida and Azospirillum brasilense. Lastly, cultivated cardoon leaf extracts were assessed in vitro for the control of several microorganisms of agriculture and food interest. All the extracts showed an important antimicrobial activity.