Evaluation Of The Allelopathic Effects Of Residues And Aqueous Extract Two Wheat Cultivars On (Avena Fatua L.) And (Silybum Marianum L.)

Abstract

The experiment was conducted in Wasit Province, Iraq, during the 2024 growing season to evaluate the allelopathic effects of two wheat (Triticum aestivum L.) cultivars, Jihan and Aba-99, on the suppression of weed growth. The results showed that both root and shoot residues of the cultivars markedly reduced the germination and growth of two major weedswild oat (Avena fatua L.) and milk thistle (Silybum marianum L.)with variations in the magnitude of inhibition depending on the wheat cultivar and type of residue. The ‘Jihan’ shoot residues exhibited the most pronounced allelopathic activity, achieving complete inhibition (100%) of wild oat germination and a 44.6% reduction in its biomass. For milk thistle, the germination percentage was reduced by 76.1%, accompanied by a 68.6% decrease in biomass.

In contrast, the ‘Aba-99’ cultivar showed comparatively lower allelopathic potential, reducing wild oat and milk thistle germination by 91.3% and 52.3%, respectively, while decreasing their dry biomass by 22.6% and 56.3%, respectively. Furthermore, root and shoot length were also inhibited to varying degrees.HPLC chemical analysis identified eight allelochemicals in totalsix phenolic compounds and two terpenoidspresent in the wheat residues.