Mechanism Of Different Resistance To Clodinafop-propargyl Preparation In Wheat Varieties

Clodinafop-propargyl is one kind of herbicide inhibited the activity of acetyl coenzyme A carboxylase(ACCase)and is widely used to prevent grass weeds in wheat field.Some wheat was harmed or even reduced production after spraying clodinafop-propargyl preparation contained safener(cloquitocet-mexyl)in agricultural production.The most tolerant variety Huaimai 23 and the weakest tolerance variety Ningmai 16 were dealed with clodinafop-propargyl and safener respectively,oxidase activities and isozymes,metabolization enzymes and target enzyme were investigated and the amine acid sequences of the CT domain in target enzyme was analysis.The purpose of this paper was to clarify the reasons of the resistance difference in wheat varieties to clodinafop-propargyl,and to provide a theoretical basis for its safe application.The activity of peroxidase(POD)in Huaimai 23 was higher than that in Ningmai 16 in control.The increment of POD activity in Huaimai 23 was less than that in Ningmai 16.When wheat was treated with clodinafop-propargyl at the dosage of 72g a.i.·ha-1 and 144g a.i.-ha-1 alone or mixed with cloquitocet-mexyl 5 days later,the activity of POD in Huaimai 23 improved remarkably,the activity of POD in Ningmai 16 started to improve at the third day after treatment at the dosage of 144g a.i.·ha-1.The activity of POD in both Huaimai 23 and Ningmai 16 didn't change when treated with safety alone.The activity of superoxide dismutase(SOD)in Huaimai 23 was lower than that in Ningmai 16,but it was increased rapidly in wheat treated,and reached maximum at 7 days after treatment.The increment of SOD activity in Huaimai 23 was less than that in Ningmai 16 too.The isozyme of POD and SOD were analyzed by polyacrylamide gel electrophoresis(PAGE),the results showed that the isozyme was difference in varieties,and isozyme bands were no changed by clodinafop-propargyl or cloquitocet-mexyl treated.The expression level of metabolic enzymes genes(CYP1C6V1and GST)were increased after treated by clodinafop-propargyl or cloquitocet-mexyl,and when the dosage was higher the range of change was greater.The low dosage treatment of clodinafop-propargyl mixed with cloquitocet-mexyl had no influence on the expression level of P450 gene in Huaimai 23,but increased the expression in Ningmai 16.High expression level of P450 gene in Huaimai 23 was observed during the experimental period,and the expression level in Ningmai 16 reached maximum at 3 days after treatment,then decreased slowly with high dosage treatment of clodinafop-propargyl.When varieties were treated with clodinafop-propargyl and cloquitocet-mexyl,the expression level of GST gene was increased firstly then showed a downward trend,the trend and the range of exchange were the same in two varieties.Clodinafop-propargyl inhibited the expression level of ACCase gene in leaf of Huaimai 23 and Ningmai 16,and when the dosage was higher,the gene expression was lower.What's more,the inhibitory effect on Ningmai 16 was stronger than that of Huaimai 23.Safener(cloquitocet-mexyl)didn't affect the its expression.With the growth of wheat,the inhibition of ACCase gene in the leaves of two wheat varieties was gradually alleviated,and their expression increased slowly.However,the expression level of ACCase gene in the leaves of Ningmai 16 treated clodinafop-propargyl at 144g a.i.·ha-1 was consistently lower than that of Huaimai 23.In Huaimai 23,the sequences of ACCase CT domain gene was 130bp more than that in Ningmai16.Vector NIT was used to translate the sequence into polypeptide chains composed of amino acid residues.The sequences of ACCase CT domain gene in Huaimai 23 had an opened reading frame(ORP)of 1737 bp which encoded 579 amino acid residues and in Ningmai 16 had an opened reading frame(ORP)of 1707 bp which encoded 569 amino acid residues.By comparison,the amino acids of the two wheat began to vary at 552 loci,the amino acids of Ningmai 16 was highly homologous with those of grass weeds which was sensitive to clodinafop-propargyl such as Lolium perenne L,Avena fatua L,Alopecurus myosuroides Huds,etc.In summary,the different activity of POD and SOD between Huaimai23 and Ningmai 16 had no significant effect on their resistance to clodinafop-propargyl.The different expression of P450 and GST gene in response to clodinafop-propargyl in two varieties was one of the factors that Huaimai 23 had stronger resistance than Ningmai 16.There were no significant effect on the activity of both POD and SOD in two varieties after the safener(cloquitocet-mexyl)treatment,the expression level of ACCase gene as well,and the expression level of P450 and GST gene was increased,thus the safener was one of the factors that Huaimai 23 had stronger resistance than Ningmai 16.However,the different expression of ACCase gene and difference in their CT domain sequences played a pivotal role.