Occurrence of Bensulfuron-Methyl Resistance and Target-Site Resistance Mechanisms in Biotypes from Paddy Fields.

is a troublesome broadleaf weed, widely distributed in the paddy fields of southern China. In this study, 10 biotypes of were sampled from Yangzhou City, China, where the paddy fields were seriously infested with , and their resistance levels to acetolactate synthase (ALS) inhibitor bensulfuron-methyl were determined. The whole-plant response assays showed that nine biotypes were highly resistant (from 16.4- to 183.1-fold) to bensulfuron-methyl in comparison with a susceptible YZ-S biotype, and only one YZ-6 biotype was susceptible. gene sequencing revealed that three gene copies existed in , and four different amino acid substitutions (Pro197-Leu, -Ala, -Ser, and -His) at site 197 in the or genes were found in eight resistant biotypes. In addition, no amino acid mutations in three genes were found in the YZ-3 biotype. These results suggested that target-site mutations or non-target-site resistance mechanisms were involved in tested resistant biotypes. Finally, a cleaved amplified polymorphic sequence (CAPS) marker was identified to rapidly detect the Pro197 mutations in .