Cyperus brevifolius is a perennial weed in turf grass on golf courses. Recently, some populations of C. brevifolius have been found to survive after application of sulfonylurea herbicides in turf grass. In this research, responses to halosulfuron-methyl and flazasulfuron sulfonylurea herbicide, were examined and the gene encoding acetolactate synthase (ALS) was determined in four accessions that were collected from the survived populations. All the four accessions survived after the treatment with halosulfuron-methyl at a recommended dose of turf in a pot experiment. Analysis of ALS gene revealed that the ALSs of the five accessions have amino acid substitutions; either of Asp376Glu, Pro197Ser or Trp574Leu, which are known to cause sulfonylurea resistance. Thus, sulfonylurea resistant biotypes were found in C. brevifolius in turf grass in Japan, and the resistance was assumed to be caused by amino acid substitutions of ALSs.
