Common allelochemicals in root exudates of Barnyardgrass (Echinochloa crus-galli L.) and inhibitory potential against rice (Oryza sativa) cultivars

ABSTRACT: The present study was conducted to analyze allelochemicals by HPLC method in Barnyardgrass root exudates. The pure seeds of barnyardgrass were collected and grown in hydroponics system to study their root exudates effects on germination and seedling growth parameters of four rice cultivars (Neda, Nemat, Dullar and IR60). Experiment was evaluated in a factorial arrangement with two factors in a completely randomized design with four replications. Barnyardgrass root exudates obtained from hydroponics was qualified and quantified with HPLC method. Among of detected phenolic acids, the highest content was related to p-hydroxybenzoic acid (4.3 mg/l) and the lowest amount was belong to cinnamic acid (0.91 mg/l). Root exudates had the highest inhibitory activity on root length of Dullar cultivar (by 45.85% inhibition) and the lowest amount was belong to IR60 cultivar (by 31.13% inhibition). the highest inhibition of protein content (by 16.61%) was related to 100% concentration of root exudates on Dullar cltivar and the lowest inhibitions (by 9.63, 9.74 and 9.81%, respectively) were belong to Nemat, IR60 and Neda cultivars in 50% concentration of root exudates. Furthermore root exudates of Dashtisard had a least inhibitory effect on all studied traits. It seems that, if a blend of compounds is responsible for the observed growth inhibition of rice, phenolic acids such as p-hydroxybenzoicacid could play the key roles, because of this compound detected in higher range than the other allelocemicals