Allelopathic Effects of Three Cultivars of Rapeseed (Brassica napus L.) Aqueous Extracts at Different Concentrations on Germination and Seedling Growth of Some Weeds

Allelopathy is an interference mechanism in which living or dead plants releaseallelochemicals exerting an effect (mostly negative) on the associated plants, and this might be a chance to reduce the use of herbicides and could be an additional tool to control herbicide-resistant weeds. The species of Brassica tissue such as rapeseed could beattributed to their ability to release toxic substances in the environment and to create anunfavorable environment for weed germination and establishment. The objective of thisstudy was to select suitable cultivars of rapeseed with high allelochemical and use of themin weed management. Accordingly, an experiment was carried out to assess allelopathicpotential of cultivars of rapeseed vegetative parts on some common weeds in Kermanshahregion (wild barley, wild oat, tumbleweed amaranth and curly dock) in randomizedcompletely block design. The factors consisted of cultivars (opera, talaieh and okapy) ofrapeseed and concentration (100%, 50% and control).Measured traits were germinationpercentage, inhibitory percentage, speed of germination, rootlet length and hypocotyllength. The bioassay experiments showed that by increasing the aqueous extractconcentrations of rapeseed’s cultivars, the germination rate and seedling crops of weed were decreased (P < 0.001). Especially the residual extract of rapeseed had most effect on germination and seedling growth of tumbleweed amaranth. In particular, opera extractscaused greater inhibitory percentage on weeds than talaieh and okapy.