Allelochemicals identified from Jerusalem artichoke (Helianthus tuberosus L.) residues and their potential inhibitory activity in the field and laboratory

Weed management systems often seek biological solutions to minimize the environmental impacts related to the use of herbicides in agricultural systems. The suppressive effects of allelochemicals can sometimes be used effectively to provide biological pest and weed control. Jerusalem artichoke (Helianthus tuberosus L.) has been reported to be a highly invasive weed in European cropping systems, but this plant is also gaining interest as a cultivated crop in Italy. The aim of this study was to investigate the impact of Jerusalem artichoke and its extracts upon the germination and growth of seedling weeds and crops. HPLC coupled to MS was used for identification of the compounds associated with the observed growth inhibition. The weed suppressive activity of local biotypes of Jerusalem artichoke on weed growth and establishment was also evaluated in a field experiment. Shoot extracts of the cultivar Fuseau were consistently most inhibitory to germination and seedling growth of lettuce, particularly the diethyl ether extract. Solvent partitioning of the aqueous extracts of dried artichoke shoots resulted in greater inhibition in comparison to the aqueous extract itself. The diethyl ether extract provided 2-fold greater growth inhibition, in comparison to the aqueous extract, at concentrations of less than 0.5 mg extract per Petri dish. HPLC MS evaluation of the diethyl ether extract led to the identification of salicylic acid (o-hydroxybenzoic acid), and the closely related compound p-hydroxybenzaldehyde, as well as minor quantities of o-coumarinic acid and coumarin in the active fraction inhibiting lettuce seedling growth. Field observations provided further evidence for the allelopathic potential of H. tuberosus residues, as significant weed growth inhibition was observed in Jerusalem artichoke-infested plots with soil-incorporated residues in comparison to non-infested field sites, both in terms of weed seedling emergence and growth. The allelopathic potential of H. tuberosus may be of interest in the implementation of integrated weed management programmes by considering the suppressive ability of this plant and its residues for weed management in the field.