Non-target-site and target-site resistance of Beckmannia syzigachne Steud.to AHAS inhibitors in China

【摘要】：American sloughgrass(BeckmanniasyzigachneSteud.) is one of the most competitive and malignant weeds in rice-wheat rotation areas of China.American sloughgrasswere not sensitiveto Acetohydroxyacid synthase(AHAS) inhibitors.There were two resistant American sloughgrass populations(R1 and R2) showed resistance to inhibitors of AHAS by using whole-plant dose-response assay,DNA sequencing and in vitro AHAS enzyme assay.Whole-plant dose-response assay indicated that Rl showed moderately resistant to mesosulfuron-methyl(3.3-fold),flazasulfuron(4.7-fold),imazapic(2.8-fold),pyroxsulam(1.6-fold) and pyribenzoxim(7.4-fold),and highly resistant to tlucarbazone(11.7-fold).However,using malathion which is a cytochrome P450 inhibitors combined with mesosulfuron-methyl could reduce the level resistance of Rl.Furthermore,R2 was highly resistant to flazasulfuron(34.9-fold),imazapic(11.3-fold),flucarbazone(49.2-fold),pyribenzoxim(12.9-fold),moderately resistant to mesosulfuron-methyl(9.8-fold) and pyroxsulam(6.3-fold).Amplified partial AHAS gene was sequenced and in vitro AHAS enzyme was assayed in order to clarify the resistance mechanism of American sloughgrass populations.The results showed that R2 had Pro-197-Ser mutation in the AHAS genewhich resulted in the R2 resistance to AHAS inhibitors.There was no mutation in AHAS gene in Rl and also no significant differences in enzyme sensitivity between the susceptible(S) and resistant population(Rl),enhanced the metabolism may be the main mechanism of Rl resistance to AHAS inhibitors.