Preliminary Study Of The Resistance Mechanism To Cyhalofop-butyl-resistant Leptochloa Chinensis In Paddy Field Of Hunan Province

Leptochloa chinensis（L）Nees,one of the most noxious weeds in paddy fields of different regions in Hunan province,was chosen as a main research object in this paper.The susceptibility of L.chinensis to cyhalofop-butyl were investigated by whole-plant bioassay experiments which were also carried out to evaluate the resistance level.Study on the resistance mechanism of the resistant L.chinensis population to cyhalofop-butyl,resistance mechanism of L.chinensis to cyhalofop-butyl were determined.The susceptibility of LC19027 to Acetyl-coenzyme A carboxylase（ACCase）inhibitors herbicide were researched by whole-plant bioassay experiments which were also carried out to evaluate the cross-resistance levels of LC19027.Two enzyme inhibitors（NBD-Cl,malathion）and cyhalofop-butyl were used together,the relationship between the resistance of LC19027population to cyhalofop-butyl and metabolic enzymes were determined.The metabolic enzyme gene of LC19027 population to cyhalofop-butyl were preliminarily determined by transcriptome sequencing technology.The main results are as follows:Single dose response was used to determine the susceptibility of 38 L.chinensis populations from Hunan province to cyhalofop-butyl.Preliminary results indicate that 30populations were sensitive to cyhalofop-butyl,and 8 populations were resistant.Whole-plant dose-response bioassay was used to determined the resistance level of eight resistant populations to cyhalofop-butyl.The GR₅₀value of the most sensitive LC19007-3 population was 14.67 g a.i.ha^-1as control,the results show that there were one low resistance population,four moderate resistance,two high resistance and two extremely high resistance population.The ACCase CT functional domain genes of the eight resistant populations were cloning and sequence analysis.By comparing the gene sequences of eight resistant populations and susceptible population LC19007-3.Among them,seven populations had mutations at the seven recognized amino acid sites of ACCase CT 1781,1999,2027,2041,2078,2088,and 2096,the 2027 amino acids of ACCase mutated from tryptophan（Trp）to cysteine（Cys）in five resistant populations,the 1999 amino acids of ACCase mutated from tryptophan（Trp）to cysteine（Cys）in one resistant populations,the 2041 amino acids of ACCase mutated from isoleucine toasparagine.No known resistance-related mutations were found in the LC19027 resistant populations.The susceptibility of LC19027 to five ACCase inhibitors herbicide were researched by whole-plant bioassay experiments which were also carried out to evaluate the cross-resistance levels of LC19027.The results show the RI of the resistant population to the herbicides were 3.218,4.223,3.627,5.867 and 0.864 respectively,therefore,the LC19027population expressed resistance to ACCase inhibitors herbicide such as haloxyfop-R-methyl,clodinafop-propargyl,metamifop,and Fenoxap-rop-P-ethyl,but not to clethodim.Detection of reversal effect of LC19027 to cyhalofop-butyl resistance by the cytochrome P450s inhibitor malathion and glutathione S-transferase（GSTs）inhibitor4-chloro-7-nitrobenzoxadiazole（NBD-Cl）.The GR₅₀value of LC19027 to cyhalofop-butyl without NDB-CL and malathion was 19.037g a.i.ha^-1,the GR₅₀value of LC19027 to cyhalofop-butyl plus NBD-C l and malathion were 8.496 g a.i.ha^-1and 5.445 g a.i.ha^-1respectively.The resistance of LC19027 to cyhalofop-butyl was significantly reversed by two metabolic enzyme inhibitors.Transcriptome sequencing was used to analyzed and excavated of metabolic enzyme genes of LC19027 to cyhalofop-butyl resistance.Compared with the sensitive population,the resistant LC19027 population included CYP90D2,CYP74A4,CYP71D55,CYP75B3,CYP707A5,CYP710A1,CYP88A1,GSTF1,Glycosyl transferases group 1,Glycosyl transferase family 21,Glycosyl transferase family group 2and ABC1 were significantly upregulated.In summary,this study determined the resistance level of L.chinensis to cyhalofop-butyl in paddy fields,and the resistance mechanism was preliminarily clarified.It provides theoretical basis for the control of L.chinensis in paddy fields.