Whole plant Response and Acetolactate Synthase Activity of Sulfonylurea-Resistant Monochoria korsakowii Occurred in Paddy Fields of Korea

This experiment was conducted to determine the difference of growth response and acetolactate synthase (ALS) activity between sulfonylurea(SU)-resistant and -susceptible Monochoria korsakowii to sulfonylurea herbicides. The apparent resistance to SU herbicides, including azimsulfuron, bensulfuron-methyl, cinosulfuron, ethoxysulfuron, imazosulfuron and pyrazosulfuron-ethyl, was confirmed in greenhouse tests. The susceptible biotype was controlled completely at the recommended doses of all the herbicides tested, but the resistant biotype survived. The rate () of the six SU herbicides required to reduce fresh weight by 50% was about 5- to 144-fold higher in the resistant biotype than in the susceptible biotype. ALS activity isolated from the resistant biotype was less sensitive than that of the susceptible biotype. The herbicide concentration required to inhibit ALS activity by 50% () was 14- to 76-fold higher as compared to the susceptible biotype