Study On Mutiple Resistance And Mechanism To Three Herbicides In Echinochloa Oryzicola (Vasing.) Vasing.

Echinochloa oryzicola(Vasing.)Vasing.is one of the common pernicious weeds in rice fields in Northeast China,resulting in seriously harmed the yield and quality of rice.Penoxsulam,metamifop and quinclorac are special agents for the control of E.oryzicola in Chinese rice fields.In the early stage,they had good control effect on E.oryzicola,but their control effect has decreased significantly in recent years.The objectives of this study were: to determine the multiple resistance to three main agents in 32 E.oryzicola populations that were collected from Northeast China by whole-plant dose-response;to explore the target resistance mechanism by sequencing of target enzyme gene and determination of target enzyme activity in vitro;to analyze the differences of β-CAS activity by physiological and biochemical methods;to determine the P450s activity difference by malathion as P450s inhibitor.Therefore,a preliminary theoretical basis for the resistance monitoring were provided for improving the scientific prevention and control of E.oryzicola in Northeast China.The sensitivity test of 32 E.oryzicola populations to three herbicides were determined by single dose screening test,which showed that 23 of 32 E.oryzicola populations were resistant to penoxsulam,17 of 32 E.oryzicola populations were resistant to metamifop and 9 of 32 E.oryzicola populations were resistant to quinclorac,The resistance frequency was high,reaching to 81.25%.In these resistant populations,HLJ4,LN1 and LN24 were screened as suspected multiple resistant populations with resistance to all three herbicides.Furthermore,their resistance levels were evaluated by the whole-plant bioassay.The results showed that HLJ4,LN24,LN1 exhibited low to high resistance levels of resistance to penoxsulam with resistance indexes of 4.80,8.66,25.67,respectively;HLJ4 and LN1 populations exhibited relatively high resistance levels of resistance to metamifop with resistance indexes of 10.64 and 23.59 respectively,LN24 exhibited medium resistance level with resistance indexe of9.86;HLJ4 exhibited a high level of resistance to quinclorac,and LN1 and LN24 exhibited a very high level of resistance to quinclorac with resistance indexes of 65.85,145.21 and269.60,respectively.The gene sequencing was used to determine sequence differences of target enzymes ALSand ACCase between suspected multiple resistant and suspected sensitive populations.By comparison,no gene mutation was observed in the suspected multiple resistant populations.The results of target enzyme activity in vitro showed that there was no obvious difference in the sensitivity of target enzymes ALS and ACCase between three suspected multiple resistant populations and suspected sensitive population,with the resistance indexs of 1.06-1.38.It was concluded that the multiple resistance of the three populations to penoxsulam and metamifop was not caused by the mutation of target enzyme gene or the enhancement of target enzyme activity.The study of β-CAS activity showed that the change of β-CAS activity in different populations was significantly different after quinclorac application.The β-CAS activity of LN24 was induced,and always higher than that of the control group.And the maximum activity of β-CAS appeared after 7d,which was 1.72-fold to the control.The activity of HLJ4 and LN1 firstly decreased slightly and then recovered to the initial level,while the the activity of LN12 showed no significant change until death.It was concluded that resistance of LN24 population to quinclorac was related to the induction of β-CAS activity.The effect of malathion as the P450s inhibitor was studied on the resistance level of three multiple resistant populations,and the results showed that malathion could significantly reduce the resistance of three multiple resistant populations to penoxsulam,and the resistance index ratios were 1.99,5.42 and 1.60 before and after malathion application,respectively.The resistance of LN1 to metamifop and HLJ4 to quinclorac were also significantly decreased,with the resistance index ratios of 5.21 and 6.37 before and after malathion application,respectively.Therefore,these results suggested that the multiple resistance to three herbicide was related to the activity of P450s.