Abstract:

【Objective】 In recent years, Monochoria korsakowii has been a serious problem in paddy fields in northeast of China. It has become a weed which is very difficult to control by bensulfuron-methyl in some areas in the region. The objective of this study is to understand the molecular basis of the resistance mechanism to bensulfuron-methyl in Monochoria korsakowii and to find the specific mutation sites in amino acid sequence of acetolactate synthase (ALS) in the resistant Monochoria korsakowii biotype. 【Method】Using the PCR method, fragments that encode the ALS were cloned from Monochoria korsakowii, susceptible (S) and resistant (R) biotypes to bensulfuron-methyl respectively, and sequenced subsequently. 【Result】 The result showed that the nucleotide sequence of R M. korsakowii biotype differed from that of the S biotype by three nucleotide substitutions, that were proline (Pro) 197 substituted by histidine (His), methionine (Met) 200 by valine (Val), and arginine (Arg) 388 by histidine (His),among those, the amino acid substitution of Pro197 (CCT) to His (CAT) had been reported in many other resistant weeds. 【Conclusion】 It is clear that the substitution of Pro197 may be responsible for the resistance to bensulfuron-methyl in the R M. korsakowii biotype. The functions of the other two mutations in the R biotype need to be further investigated.

Key words: acetolactate synthsas, bensulfuron-methyl, Monochoria korsakowii, herbicide resistance