Genotype and harvest time affect the allelopathic activity of Cynara cardunculus L. extracts on Amaranthus retroflexus L. and Portulaca oleracea L.

Aurelio Scavo is a PhD Student at the Department of Agriculture, Food and Environment (Di3A) of the University of Catania, Italy. His PhD focused on Cynara cardunculus L. allelopathy, with emphasis on sustainable weed control. Allelopathy refers to the ability of some plants to release harmful or beneficial secondary metabolites into the environment. The manipulation of allelopathic mechanisms between plants can produce bioherbicides to promote a chemical-free weed management program. In a first step, the allelopathic effects of leaf aqueous extracts from three C. cardunculus botanical varieties (globe artichoke, wild, and cultivated cardoon) were demonstrated on seed germination of six common weeds. Secondly, the procedures to efficiently extract allelochemicals considering costs, yields, and inhibitory activity were determined. Dried leaves proved to be the best extraction plant material, and ethanol and ethyl acetate were the best solvents. In addition, new C. cardunculus allelochemicals were found and purified. Thirdly, light stress (by plant shading) in field conditions enhanced the content of C. cardunculus allelochemicals and the phytotoxicity. In a three-year field experiment, the monoculture of globe artichoke, and cultivated and wild cardoon were found to reduce the amount of weed seeds in the soil seed bank, compared to a biennial rotation wheat/faba bean, and to improve the soil eubacterial communities. The objective was to evaluate the effect of genotype and harvest time on the phytotoxicity, quantity and composition of C. cardunculus allelochemicals. The wild and cultivated cardoon had the highest concentrations of allelochemicals. April was the best harvest time for the artichokes to produce the allelochemicals that inhibit Amaranthu retroflexus and Portulaca oleracea germination, root and shoot length, thanks to the favorable climatic conditions that stimulated the synthesis of these compounds. These results represent an important advancement in the understanding of C. cardunculus inhibitory activity and offer new eco-friendly tools to farmers for weed control.

Aurelio Scavo won an ISHS Young Minds Award for the best oral presentation at the X International Symposium on Artichoke, Cardoon and their Wild Relatives in Spain in March 2019.

Dr. Aurelio Scavo, University of Catania, via Valdisavoia 5, 95123 Catania, Italy, e-mail: aurelio.scavo@unict.it

The article is available in Chronica Horticulturae