Allelopathic potential of rice (Oryza sativa) varieties on seedling growth of barnyardgrass (Echinochloa crus-galli)

High performance liquid chromatography method was used to analyze six phenolic acids in 15 rice cultivars hull water extracts as representative cultivars collected according to the results of our previous study. Dinorado hull extract had the highest phenolic acid content among the treatments. None of the six phenolic acids were detected in Line-229 hull extract by HPLC, while, Dashti-sard had the highest p-hydroxy benzoic acid content. Phenolic contents had significant correlation with percent inhibition of root growth of barnyardgrass. Eleven of the tested cultivars were chosen and grown in hydroponics system to study their root exudates effects on growth traits of barnyardgrass seedlings, in a completely randomized design with four replications. Root exudates of Dinorado, Neda, Domsorkh and Dular showed the highest inhibitory activities of barnyardgrass growth parameters, while Line-229 root exudates had the highest stimulatory effects on growth traits of this plant. Rice root exudates obtained from nine cutivars hydroponics were also qualified and quantified with HPLC method. No vanilic acid or ferulic acid was detected in cultivars root exudates. Anbarbu, Usen and Dasht rice root exudates had the highest, and Line-229 had the lowest amount of the total phenolics content.