Inhibitory Effects of Brassicaceae Cover Crop on Ambrosia artemisiifolia Germination and Early Growth

Abstract

Several cover crops (CCs) exert allelopathic effects that suppress weed growth. The aim of the present study was to evaluate the effects of aqueous extracts containing different concentrations [0, 0.5, 1, 2.5, 5, 7.5 and 10% (<i>w</i>/<i>v</i>)] of Brassicaceae CCs (<i>Sinapis alba, Raphanus sativus, Camellina sativa)</i> and of the CCs <i>Fagopyrum esculentum</i> and <i>Guizotia abyssinica</i> on germination and early growth of <i>Ambrosia artemisiifolia</i> L. The allelopathic effects were species and concentration-dependent. <i>C. sativa</i>, for example, caused the greatest potential to inhibit germination, shoot, radicle length and fresh seedling weight, whereas <i>S. alba</i> and <i>R. sativus</i> inhibited germination and early growth of <i>A. artemisiifolia</i> only at concentrations ≥7.5%. In contrast, no inhibition was observed when aqueous extracts of <i>F. escultneum</i> and <i>G. abyssinica</i> were added at any of tested concentration. Liquid chromatography-tandem mass spectrometry detected 15 phenolic compounds in Brassicaceae CCs with the highest content (µg/g) of vanillin (48.8), chlorogenic acid (1057), vanilic acid (79), caffeic acid (102.5) and syringic acid (27.3) in <i>C. sativa</i>. Our results suggest that <i>C. sativa</i> is the most allelopathic CCs and that the fruits of <i>C. sativa</i> are the plant organs richest in allelochemicals.