Allelopathic herbicidal potential and quantification of allelochemicals from swamp rice field

We evaluated the allelopathic potential of allelochemicals present in the swamp rice (Oryza sativa L.) varieties. The effects of 10-swamp rice varieties (Inpara 1, Inpara 2, Inpara 3, Inpara 4, Inpara 5, Inpara 6, Inpara 7, Inpara 8 Agritan, Inpara 9 Agritan and Inpara 10 BLB) were studied on two weeds (Echinochloa crus-galli and Monochoria vaginalis). The allelochemicals released as root exudates from these swamp rice varieties were quantified in root and soil samples with high-performance liquid chromatography (HPLC). The results showed that the swamp rice varieties differed in inhibiting the growth of E. crus-galli and M. vaginalis. The variety Inpara 7 caused maximum growth suppression of E. crus-galli (23.9 %) and M. vaginalis (29.3 %) than other varieties. Furthermore, Inpara 3, 4, 6, 7 and 8 varieties also suppressed the growth of test weeds. HPLC analysis indicated that the allelochemicals concentration was significantly higher in roots than in soil, depending on the variety. The p-hydroxybenzoic acid content in the roots was higher than ferulic and p-coumaric acids, but the release of p-coumaric acid contents into the soil was higher than other compounds. The Inpara 3 roots contained higher contents of ferulic and p-coumaric acids than other varieties, while the highest p-hydroxybenzoic content was found in Inpara 2. The ferulic and p-coumaric acids were significantly correlated with weed growth variables. These compounds may play important roles in regulating rice allelopathy.