The Resistance Of Tausch’s Goatgrass(Aegilops Tanschii Coss.) To Mesosulfuron-methyl And Screening Of Herbicides And Synergistic Adjuvants For Its Control

Aegilops tauschii an annual or biennial grass weed,is classified as Aegilop.Because of its rapid reproduction,easy spread and strong adapt ability,it has seriously affected the production and quality of winter wheat in China.As a kind of gramineous weed closely related to the genetic background of wheat,Aegilops tauschii has strong tolerance to most herbicides,poor pesticide selectivity and difficult chemical control.At present,mesosulfuron-methyl is mainly used in production to control Aegilops tauschii,but due to long-term single use,the effect of mesosulfuron-methyl on Aegilops tauschii is getting worse.Aegilops tauschiiwas chosen as a main research object in this paper,and the synergistic effects of different adjuvants on mesosulfuron-methyl and isoproturon are explored through greenhouse studies.In addition,the herbicide resistance mechanism of Aegilops tauschii to mesosulfuron-methyl was studied from the target ALS and non-target metabolism.The main results are as follows:1.Forty-five Aegilops tauschii populations was treated with mesosulfuron-methyl（15.7g a.i./hm²）at the recommended rate on the whole plant level.In total,5 populations were sensitive（S）,while 40 populations were resistant（R）to mesosulfuron-methyl.The resistance levels of mesosulfuron-methyl was measured on sixteen Aegilops tauschii populationson the whole plant level.The results showed that there was some difference in the resistance levels of Aegilops tauschii to mesosulfuron-methyl in different populations.Compared with the sensitive population 17-SD-40,the resistance index was between 2.6-9.1 times,of which,the17-HN-04 population had the highest resistance to mesosulfuron-methyl.2.Four resistance populations and sensitive populations were selected for ALS gene sequence alignment.The result showed thatthere were on known ALS resistance mutations in Aegilops tauschii population.Then,the target enzyme ALS activity was measured in vitro.There was no significant difference in ALS activity in vitro between the sensitive 17-SD-40and resistant 17-HN-04 populations.3.The changes of GSTs activity in different susceptible populations were studied by using CDNB as substrate.The result showed that the 17-HN-04 population had a higher enzyme activity,the highest level of which was 1.62 times that of the control treatment,while the 17-SD-40 activity of the sensitive population was 1.28 times.In addition,by adding GSTs inhibitor（NBD-Cl）,the sensitivity of 17-HN-04 population to mesosulfuron-methyl is reduced,and GR₅₀value decreased 25.78%.The P450s inhibitor malathion can increase the sensitivity of Aegilops tauschii to mesosulfuron-methyl.The GR50 value of 17-HN-04 and17-SD-40 population decreased 37.92%and 20.12%respectively.It can be seen that there is higher P450s activity in 17-HN-04 population.4.The LC-MS/MS method was used to determine the residual rate of mesosulfuron-methyl in resistant and sensitive populations of application of mesosulfuron-methyl.The results showed that the metabolic efficiency of mesosulfuron-methyl in the 17-HN-04 population was much higher than that in the 17-SD-40population,and the metabolic rate was reduced after adding malathion.The metabolic rate of the 17-HN-04 population decreased by 35.84%and 32.47%after 1,2 days of application of mesosulfuron-methyl.The above results indicate that the enhanced metabolism of metsulfuron-methyl by P450s and GSTs is one of the important reasons for the resist ance of the 17-HN-04 population.5.In this study,the sensitivity of Aegilops tauschii to 11 herbicides were evaluated by greenhouse studies.The results showed that only mesosulfuron-methyl and isoproturon could achieve the purpose of controlling Aegilops tauschii at the appropriate doses.Its control effects reached 65.83%-78.03%and 69.18%-87.27%,respectively,while the other herbicides were nearly ineffective.It shows that there is no better alternative to mesosulfuron-methyl except for isoproturon.6.The growth period of Aegilops tauschii has a great influence on the effectiveness of herbicides.When applied at the 2-3 and 4-leaf stage of Aegilops tauschii,the control effect of mesosulfuron-methyl（15 g a.i./hm²）and isoproturon（1300 g a.i./hm²）to Aegilops tauschii decreased 30.81%and 43.92%respectively.7.The synergistic effect of different adjuvants on mesosulfuron-methyl and isoproturon along with their optimal ratio were determined.Results indicated that ethyl and methyl ester vegetable oil,organosilicone 408presentedthe best significant synergistic efficiency with mesosulfuron-methyl,with 0.5%and 0.1%（v/v）of the mesosulfuron-methyl spray volume,respectively;and 15.21%and 26.52%control efficiency increase were founded when compared with mesosulfuron-methyl applied alone.For isoproturon,the optimum content of isotridecyl alcohol polyoxyethylene ether,polyalkyleneoxide modified heptamethyltrisiloxane,ethyl and methyl ester vegetable oil were 0.1%,0.05%and 0.25%of its spray volume,respectively;these three adjuvants showed significant synergistic effect on isoproturon with increases of 26.24%,21.8%and 25.99%.8.The field experiment results showed thatmesosulfuron-methyl and isoproturon have significantly improved the control effect on Aegilops tauschii.Ethyl and methyl ester vegetable oilhave higher synergistic effects on both herbicides,and their fresh weight control effects increased by 15.1%-18.9%,24.6%-26.6%,respectively.In summary,this study clarified the resistance level of methylsulfuron-methyl in the Aegilops tauschii population in Henan and Shandong.Revealed that the resistance of Aegilops tauschii to mesosulfuron-methyl is not necessarily related to the target ALS.Studies on the whole plant level or enzyme level of two metabolic enzymes,GSTs and P450s,have proven that the tolerance mechanism of Aegilops tauschii to herbicides includes the combined effects of the metabolic enzymes GSTs and P450s.This study evaluated the sensitivity of Aegilops tauschiito different herbicides and the synergistic effects of different adjuvants on mesosulfuron-methyl and isoproturon.The results would provide theoretical basis for enhancing control of Aegilops tauschii.