The hairy root of Fagopyrum tataricum (Tartary buckwheat) has been shown to produce allelochemicals that have herbicidal activity. The hairy root culture technique has been previously employed with F. tataricum to isolate several phenolic compounds. The purpose of this study was firstly to optimise the hairy root culture of F. tataricum using different growth media, supplemented with varying concentrations (0.1-1.0 mg L )1 ) of auxin, for phenolic compound production and secondly to evaluate the phenolic compounds for herbicidal activity to different weed species both in growth chamber and in glasshouse studies. The results suggest that hairy roots grown in half-strength Schenk and Hildebrandt medium showed the highest levels of growth (10.8 g L )1 ) and the maximal production of gallic acid, chlorogenic acid and rutin. Among the different auxin treatments, indole-3-butyric acid at 0.5 mg L )1 produced 24% more hairy root mass than the control. Hairy root extracts of F. tataricum suppressed germination and shoot and root growth in tested weeds, with the grass weed species showing greater susceptibility than the broad-leaved weed species in a growth chamber bioassay. In the glasshouse experiments, post-emergence application of the extract on 21-dayold seedlings had a greater inhibitory effect than the pre-emergence application of hairy root extract. Setaria viridis and Aeschynomene indica were the most susceptible species among grass and broad-leaved weed species, respectively. This study demonstrated that hairy root extract of F. tataricum contained allelopathic compounds and that their phytotoxicity varied with weed species.

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