Effect of Sulfonylurea Herbicides on Acetolactate Synthase Activity of Resistant and Susceptive Biotypes of Arrowwheed

The sulfonylurea(SU) resistant biotypes of S. sagittrifolia were found in the paddy fields in Yanbian region in 2000 and 2002. The inhibiting effect of the SU on acetolactate synthase activity(ALS) of SU resistant biotypes is lower than susceptive biotypes. The coefficient(RI50/SI50) of resistance to bensulfuron and to pyruzasulfuron in resistant biotypes was 57.3 and 20.0 respectively. It has been found that the cross-resistance occurred between bensulfuron and pyruzasulfuron. The research results suggest that SU-resistant for sulfonylurea herbicides was dulled to ALS of SU-resistant biotypes.