Annual Bluegrass (Poa annua L.) Herbicide Resistance Caused By ALS Gene Mutation

Acetolactate synthase(ALS) inhibiting herbicide is widely used for control of annual bluegrass(Poa annua L.) infested in zoysiagrass fairway. Field experiments were conducted 2015 and 2016 to investigate ALS-inhibiting herbicide resistance of annual bluegrass in Ansung Benest Golf Club (AB G.C) of Korea where was poorly controlled for 2 years after application of trifloxysulfuron (0.008g m^-2). As results, control of annual bluegrass was significantly less (<34%) in flazasulfuron, foramsulfuron and trifloxysulfuron treatments than that of asulam treatment (83%). In dose-response experiments, the resistant annual bluegrass survived (>80%) 40 DAT in flazasulfuron, foramsulfuron and trifloxysulfuron treatments which were applied 10 times of labeled rates. DNA sequencing results indicated that the resistance of annual bluegrass was associated with the tryptophane to leucine target-site mutation at ALS codon position 574. These results confirm the risk of annual bluegrass herbicide resistance at golf courses in Korea and suggest the needs of new herbicides that may be effective of delaying or avoiding herbicide resistance.