| Temperature affects the bioactivity of insecticides to insects.Under different temperatures,the bioactivity of insecticides to insects varies greatly with the variety of insecticides and the species of insects.Temperature not only affects the absorption,penetration and distribution of insecticides on the surface of insects,but also the insecticide targets sensitivity and the detoxification metabolic processes.In recent years,diamide insecticides have received widespread attention due to their novel mechanism of action,excellent control effect against lepidopteran insects,no cross-resistance to other types of insecticides,and safety to mammals.Therefore,in this study,the temperature effects of diamide insecticides on the bioactivity to different insects and the activity of the main detoxification enzymes of insects at different temperatures were studied and then the study carried on the related exploration at the molecular level after transcriptome sequencing.The content of this study will provide a basis for the rational selection of insecticides for the pest control according to environmental temperature and increase the utilization rate of insecticide.At the same time,it is planned to supplement and improve the research content of temperature effect of insecticides on the basis of previous studies,so as to provide ideas for the research of temperature effect of other insecticides.The results of this study are as follows:1.The temperature coefficients of diamide insecticides to a variety of tested insects were quite different.For different insects Plutella xylostella,Helicoverpa armigera,Athetis lepigone,Spodoptera exigua,Aphis gossypii and Sitobi on avenae,the temperature coefficients of indoor bioactivity of chlorantraniliprole,flubendiamide,cyantraniliprole,tetrachlorantraniliprole and tetraniliprole were determined at 15℃,20℃,25℃,30℃ and 35℃.The results showed that the five diamide insecticides showed positive temperature effects on these insects in general,but the temperature coefficients were quite different.Among them,the temperature coefficients of lepidopteran insects were higher,such as the temperature coefficient that chlorantraniliprole against S.exigua could reach up to+6527.23.2.Temperature changes during the experiment significantly affected the temperature effect of diamide insecticides on bioactivity of insect.The test insects of H.armigera were pretreated for different durations at 15℃,25℃ and 35℃ respectively.At a lower temperature of 15℃,the bioactivities of cyantraniliprole to H.armigera gradually increased with the prolonging of pretreatment durations,but the bioactivities were not affected significantly by the prolongation of pretreatment durations at 25℃ and 35℃.And at 25℃ and 35℃,the temperature coefficients showed an obvious decreasing trend with the increasing of pretreatment durations.Simulated the temperature in the field,and treated S.exigua at different time with different temperatures by tetrachlorantraniliprole.The results showed that the highest bioactivity(LC50 was 7.08 mg/L)was achieved when the test insects were treated at 11 o’clock(30℃)(the temperature gradually increased after that).The lowest bioactivity(LC50 was 31.91 mg/L)was obtained at 16 o’clock(30℃)(after which the temperature gradually decreased).In general,the persistent high temperature after exposure to diamide insecticides could help to improve the insecticidal effect.3.Different detoxification enzymes in insects had different effects on temperature effect after being treated with diamide insecticides.Carboxylesterases(CarEs),glutathione S-transferases(GSTs),multifunctional oxidases(MFOs)and UDP-glycotransferase in insects participated in the positive temperature effects of diamide insecticides with varying degrees.Among them,the effect of UGTs to the positive temperature effect of tetrachlorandiamide to P..xylostella was the most significant.The specific activity value of UGTs was 10.50 times of the control at 15℃.With the increase of temperature,the specific activity decreased,and the difference between UGTs and the control gradually decreased.Subsequently,5-nitrouracil,an UGTs inhibitor,significantly reduced the temperature coefficients of tetrachlorantraniliprole to P.xylostella,which verified that UGTs did participate in the change process of the positive temperature effect.Simultaneously,the combination of insecticide and enzyme inhibitor could significantly improve the synergistic effect of the inhibitor compared with enzyme inhibitor pretreatment.4.Related gene analysis based on transcriptome sequencing technology.The third instar larvae of P.xylostella were respectively treated with the 0.1×LC50s of tetrachlorantraniliprole(showed positive temperature effect)and chlorfenapyr(showed non-temperature effect)for 24 h,and then transcriptome sequencing was performed.After comparing the obtained sequences with the reference genome,different gene expression analysis and gene cluster analysis were conducted according to the comparison groups.And then the genes that related to GSTs,UGTs and heat shock protein were screened out.The expression of UGTs gene LOC105384687,heat shock protein gene LOC105389604,GSTs genes LOC105391548 and LOC105395140 were verified by RT-qPCR,which were consistent with the sequencing results.Thus,UGTs,GSTs and heat shock proteins were determined to be involved in regulating the positive temperature effect of tetrachlorantraniliprole to P.xylostella. |
