The methanol extracts of nine popular cultivated Vietnamese rice cultivars (Oryza sativa
L.cv. OM 2395, 5451, 6976, 380, 5930, 4498, 3536, N406, and 7347) were used to explore their
allelopathic potential on barnyardgrass (Echinochola crus-galli L.). At 0.1 g mL1, OM 5930,
OM 4498, and OM 6976 correlatively possessed greatest phytotoxicity on barnyardgrass shoot
(98.77%, 90.75%, and 87.17%) and root (99.39%, 92.83%, and 86.56%) growth. The following study
aimed to detect previously-known allelochemicals in those rice using XCMS online cloud-based
metabolomics platform. Twenty allelochemicals were semi-quantified and seven of them were
detected predominantly and five was putatively confirmed in OM 5930 (mg/ 100g fresh rice) as
salicylic acid (5.0076), vanillic acid (0.1246), p-coumaric acid (0.1590), 2,4-dimethoxybenzoic acid
(0.1045), and cinnamic acid (3.3230). These compounds were active at concentrations greater than
0.5mMand the average EC50 were 1.24 mM. The results indicated thatOM5930 may use as promising
candidates in weed biological control for rice production.