Main Article Content
The dichloromethane and methanol extracts, and the essential oil of Persicaria sp. were subjected to in vitro anti-rice pathogenic microbial activity tests. The essential oil displayed the most potential antimicrobial activity. GC-MS analysis revealed thirteen main compounds as dodecanal (54%), decanal (15%), trans-caryophyllene (8%), cyclododecane (7%) and α-humulene (5%). Strong antimicrobial activities of the oil and dodecanal were found against Rhizoctonia solani (IC50 of 0.066 and 0.851 mg/mL) and Xanthomonas oryzae pv. oryzicola (MIC/MBC of 0.78/12.50 and 0.78/25.00 mg/mL), and potent activities against Bipolaris oryzae (IC50 of 3.047 and 3.341 mg/mL) and X. oryzae pv. oryzae (MIC/MBC of 3.12/12.50 and 3.12/25.00 mg/mL). In terms of structure-activity relationship, 2-dodecanone and 2-dodecanol displayed significantly anti-fungal activity, while 1- and 2-dodecanols expressed potent anti-bacterial activity. The essential oil might be used for new microcides controlling rice pathogenic bacteria and fungi.