The basis of resistance mechanism to mesosulfuron-methyl in Tausch's goatgrass (Aegilops tauschii Coss.)

Tausch's goatgrass (Aegilops tauschii Coss.) is one of the most troublesome weeds in winter wheat-growing regions of China. In recent years, the recommended field rate of mesosulfuron-methyl failed to control the Tausch's goatgrass population in Shanxi province (SX), China. Experiments were conducted to characterize the herbicide resistance level and investigate the basis of mesosulfuron-methyl resistance in Tausch's goatgrass. Whole-plant dose response tests showed that the SX population exhibited 11.42-fold resistance to mesosulfuron-methyl than the susceptible HN population, and the resistance level in the SX population could be significantly reduced by malathion, a cytochrome P450 inhibitor. The SX population also exhibited cross-resistance to imazethapyr, pyroxsulam and bispyribac-sodium. Acetohydroxyacid synthase (AHAS) sequencing and enzyme activity assays demonstrated that the mesosulfuron-methyl resistance was not conferred by target-site substitution. A sensitive AHAS, together with the malathion revisable resistance, suggested that herbicide metabolism likely plays a main role in the mechanism of mesosulfuron-methyl resistance in the SX population. To our knowledge, this is the first report elucidating the mesosulfuron-methyl resistance in Tausch's goatgrass.