Phytotoxic activity of barnyardgrass (Echinochloa crus-galli) on some rice (Oryza sativa) genotypes

For evaluation of allelochemicals by HPLC method and phytotoxicity potential of barnyardgrass (as the main weed of paddies) a factorial experiment was employed with two factors of: tissue extracts (hull, leaf and stem) and rice genotypes (IR60, Sefidrood, Khazar, Nemat, Neda, Fajr, Tarom, Shiroodi and Hybrid). The mature plants of barnyardgrass were collected from paddy field, after separation to different parts, the tissues dried and ground then stored until extraction. The tissue extracts of Barnyardgrass were qualified and quantified with HPLC method. According to the results, the highest content of phenolic acid was related to p-hydroxybenzoic acid (4.23 mg/l in plant extraction). Among bioassay study, leaf extract of barnyardgrass had the highest inhibitory activity on root lengths of sefidrood (With 65% inhibition) and the lowest amount was belong to shiroodi cultivar (6% inhibition). Between genotypes Nemat had the highest resistance to the allelopathic activity in all tissue extracts of barnyardgrass (with 4, 2 and 1% inhibition by leaf, hull and stem extracts, respectively). The various inhibitions on seed and seedling properties of studied rice genotypes may reflect to the allelopathic potential of barnyardgrass and individual ability of rice genotypes to resistance the tough conditions. Accordingly, leaf extract of barnyardgrass for higher suppressive effects and meanwhile, p-hydroxybenzoicacid for higher concentration between other types of phenolics could play the key roles in such a mixture in similar conditions.