Allelopathic potential of some essential oils vis-à-vis three noxious weed species invading cereals

Abstract This investigation was performed to assess the allelopathic potential of essential oils extracted from seven medicinal and aromatic plants of the Tunisian flora: Artemisia herba-alba Asso., Mentha pulegium L., Rosmarinus officinalis L., Salvia officinalis L., Lavandula officinalis L., Eucalyptus gomphocephala DC. and Foeniculum vulgare Mill.; selected based on ethnobotanical data. To achieve the target, in vitro trials were carried out to test the inhibitory activity of these volatile oils against seed germination of three Mediterranean noxious weed species namely Sinapis arvensis L., Rumex crispus L. and Phalaris minor Retz.; invading most particularly grain crops. Accordingly, the same bioassays were conducted concurrently for two winter cereals wheat and barley as non-target species. The scrutiny of results revealed a differential response among weed species as well as a disparity across the essential oil activities. Indeed, solely oils from A. herba-alba, M. pulegium and L. officinalis drastically inhibited seed germination of P. minor and S. arvensis. Based on their phytotoxic potency (IC50), these most active essential oils could be subsequently ranked as M. pulegium > L. officinalis > A. herba- alba. In a second step, a phytochemical study using GC/FID and GC/MS was undertaken. The abundance of oxygenated monoterpenes might thereby explain the potent inhibitory activity of the oils. Moreover, it is worth noting that A. herba-alba essential oil exhibited a distinct chemical composition which would characterize the Tunisian Dorsale. Hence, these promising findings may solve some environmental issues related to pesticide pollution and hold the key to non-chemical weed management strategy.