Study On Resistance Of Penoxsulam In Echinochloa Crus-galli In Paddy Field

Barnyardgrass?Echinochloa crus-galli?is one of main weeds in paddy field and harmful to rice production.Penoxsulam is an acetolactate synthetase inhibitor used to control weeds in rice field usually.Chemical control technique has long been applied to control weeds in rice field as the major method.Including barnyardgrass,many weeds have become resistant to sevaral herbicide due to intensive and extensive application.The main purpose of this study is to clarify level of resistance to penoxsulam in Echinochloa crus-galli population and explore resistance mechanism of penoxsulam in Echinochloa crus-galli.In this study,the sensitivity of barnyardgrass field populations from Hubei,Hunan,Jiangxi and Anhui province to penoxsulam was assayed by whole plant bioassay method,and the dose-response curves of 16DYC,16NCB,16NXB,16XYA,16GAB and17GA were assayed.The cross-resistance of 17GA and 16NXB to other herbicides was measured.Furthermore,the metabolic and target resistance machanisms of 16NXB and17GA were studied.The main results are as follows:?1?The preliminary screen of barnyardgrass field population collected from Hubei,Hunan,Jiangxi and Anhui province in 2016 and 2017 was carried out by using 30 and 60g a.i.ha^-1 of penoxsulam.According to screening results,five populations were sensitive,and nineteen population were resistant to penoxsulam.The dose-response curves of six barnyardgrass field population 16NXB,16NCB,16XYA,16GAB,17GA and 16DYC were measured and the results showed that six population have developed different levels of sensitivity to penoxsulam.The 16DYC population showed the most sensitive to penoxsulam with the LD₅₀ of 8.73 g a.i.ha^-1.The 17GA population showed the highest resistance to penoxsulam with the LD₅₀ of 92.51 g a.i.ha^-1?relative resistance index=10.60?.The LD₅₀ of 16GAB,16NCB,16XYA and 16NXB populations were 10.61,13.20,17.22 and 17.92 g a.i.ha^-1,respectively.The cross-resistance results of 17GA and 16NXB populations to other herbicides showed that the 17GA population displayed cross-resistance to quinclorac,bispyribac-sodium and pyribenzoxim,and 16NXB population displayed cross-resistance to pyribenzoxim and bispyribac-sodium.?2?The ALS gene of the resistance field populations?17GA,16NXB?and the sensitive population?16DYC?were amplified and sequenced.Point mutations of the plant ALS gene have not been found in eight known amino acid substitutions sites in 16DYC and 16NXB populations.However,Trp-574-Leu mutation of the plant ALS gene has been found in 17GA population.The ALS sensitivity results to penoxsulam in 17GA,16NXB and 16DYC populations showed the I₅₀ of ALS in 17GA population to penoxsulam was0.1013?mol/L,and the I₅₀ of 16NXB and 16DYC population were 0.0116?mol/L and0.0072?mol/L,respectively.Compared with 16DYC population,the resistance index of17GA population was 14.07.These results indicated that the resistance of 17GA population to penoxsulam was endowed by Trp-574-Leu mutation and 16NXB population was likely non-target site resistant to penoxsulam.?4?The synergistic effect of the enzyme inhibitors on penoxsulam indicated that the three enzyme inhibitors,cyanuric chloride,malathion and PBO,could completely reverse the resistance of the 16NXB population to penoxsulam and partially reverse the resistance of the 17GA population to penoxsulam.The activities of P450 and GSTs were tested in barnyardgrass resistant and sensitive population.It was found that the GSTs activity was significantly higher in 17GA population than in sensitive population.And the GSTs and P450 activity were significantly higher in 16NXB population than in sensitive population.The espressions of P450s and GSTs genes in three barnyardgrass population were assayed by qRT-PCR.The result showed that the expressions of GST2?GST3?GSTF1?GST23?CYP81A14?CYP81A18?CYP81A12 and CYP81A21 significantly increased in 17GA population plants,and GSTF1 and CYP81A21 significantly increased in 16NXB population plants compared with 16DYC population.P450 inhibitors malathion and PBO can partially reverse the resistance of 17GA population to penoxsulam,but P450 activity.is no significant difference between 17GA population and 16DYC sensitive population.In conclusion,GSTs and P450s were related to the resistance of 17GA population to penoxsulam,but the metabolic resistance of 17GA population to penoxsulam was mainly related to GSTs,and GST2,GST3,GSTF1 and GST23 might be the main resistance genes.The resistance of 16NXB population to pfa may be related to GSTF1 and CYP81A21.