The Effect And Mechanism Of Pesticide Mixture On The Reproduction Of The Small Brown Planthopper(SBPH),Laodelphax Striatellus(Fall(?)n)

The small brown planthopper(SBPH),Laodelphax striatellus(Fallen)is one of the important agricultural pests.It mainly distributed in temperate and subtropical regions,and can damage a variety of gramineous crops,by not only injuring crops through feeding but also by transmitting virus diseases.Due to the characteristics of low toxicity,low residue,low cost,and good control efficacy,the fungicides Jinggangmycin(JGM)and Carbendazim(CBM)were used to control rice sheath blight.Moreover,studies show that JGM suppresses reproduction of SBPH but CBM stimulates the reproduction of SBPH.Triazophos(TZP)is a classic insecticide that can induce SBPH resurgence.Key genes of up-regulated expression were screened through transcriptomics analysis of SBPH treated with mixture of JGM and CBM,and key genes of down-regulated expression of SBPH treated with JGM prior to CBM treatment(i.e.CBM spray 24h after JGM spray)(JC),JGM+TZP(JMT),and JGM spray prior to TZP spray(i.e.TZP spray 24h after JGM spray)(JT)were screened in this experiment.Through the oviposition experiment,it was found that the mixture of these three agents showed two opposite results:stimulating reproduction and inhibiting reproduction.We carried out a series of physiological and biochemical experiments to investigate the related mechansim.RNAi interference was carried out on genes related to reproduction(RPL8 and RPS2),to examine the effect and mechanism of these two genes on reproduction of SBPH after mixed treatment.1.Inverse effects of mixed pesticide sprays on reproduction of SBPHCompared with the control group,JMC treatment group increased the number of eggs laid by about 32.5%,the oviposition period by about 29.5%and the female lifespan by about 19.1%.There was no significant difference between the treatment group and the control group for preoviposition period.The contents of ovarian protein,triglyceride and soluble sugar increased by 52.7%,74.7%,30.4%and 33.8%respectively,and the body weight and body shape increased by 29.5%and 19.1%respectively.The abdominal oviposition flap increased by 9.9%,3.4%and 35.2%respectively.The results showed that the JMC treatment could stimulate the fecundity,nutrients and physiological indexes of SBPHAfter treatment with JC,JMT,and JT group respectively,the number of eggs laid decreased by 25.5%,58.6%and 45.2%respectively,the preoviposition period increased by 28.9%,56.5%and 79.7%respectively,the oviposition period decreased by 18.6%,37.9%and 32.6%,and the female lifespan decreased by 5.0%,13.1%and 1.7%respectively.The contents of ovarian protein decreased by 27.3%,39.8%and 38.3%,the triglyceride content decreased by 15.0%,25.2%and 26.8%,the soluble sugar content decreased by 10.4%,6.4%and 25.9%,the body weight decreased by 3.2%,8.4%and 9.7%the body shape decreased by 3.3%,21.4%and 14.8%,and the abdominal oviposition flap decreased by 4.6%,7.6%and 6.6%,respectively.These results showed that JC,JMT,JT treatment played an important role in the reproductive nutrients and physiological indexes of SBPH2.Study on the effect of RPL8 and RPS2 on the reproduction of SBPHTranscriptomics analysis showed that the mixed spraying of JMC resulted in up-regulated expression of ribosome protein L8(RPL8),while JC,JMT and JT sprays resulted in down-regulated expression of ribosomes protein S2(RPS2)To determine the role of RPL8 in the reproduction of SBPH,dsRPL8 was injected into the 3rd instar nymph after treatment of JMC.Compared with the control group,JMC+dsGFP,JMC,the gene expression of JMC+dsRPL8 group decreased 75.2%,81.7%and 82.0%respectively,and the number of eggs laid decreased 64.4%,71.1%and 72.9%respectively,the preoviposition period was extended by 35.3%,100%and 54.4%respectively,the oviposition period was shortened by 47.0%,58.6%and 59.2%;the female lifespan was shortened by 38.2%,45.5%and 48.2%.Vg expression decreased by 75.1%,82.5%and 83.2%respectively.Briefly,When JMC treatment,the inhibitory effect of Jinggangmycin is replaced by the stimulating effect of carbendazim,showing the stimulating effect on the reproduction of SBPH,These results showed that the number of eggs laid was increased,the preoviposition period was shorted,the oviposition period was prolonged,the female lifespan was prolonged,relative RPL8 and Vg expression was upped after the JMC treatment.while JMC+dsRPL8 the opposite to JMC.These results showed that the RPL8 played an important role in the reproduction of SBPH after the JMC treatment.To determine the role of RPS2 in the reproduction of SBPH,dsRPS2 was injected into the 3rd instar nymph after treatment of control.Compared with the control group,JC group,JMT group,JT group and control+dsGFP group,after the control+dsRPS2,the gene expression of control+dsRPS2 group decreased 80.9%,75.2%60.1%,66.4%,82.4%respectively,the number of eggs laid decreased by 70.4%,65.2%,53.7%,60.2%and 71.2%;the preoviposition period increased by 74.0%,48.3%,13.3%,16.3%and 62.5%respectively,the oviposition period was prolonged by 74.0%,48.3%,13.3%,16.3%and 62.5%respectively,the oviposition period was shortened by 55.1%,49.3%,35.5%,39.9%and 57.3%respectively,the female lifespan was shortened by 31.0%,36.3%,19.0%,24.2%and 33.2%respectively.In general,when JC treatment,Jinggangmycin first inhibited the growth of SBPH,and then carbendazim did not stimulate the reproduction of SBPH,the expression of RPS2 and Vg was down regulated;After JMT treatment,because Jinggangmycin inhibited the reproduction of SBPH and Triazophos inhibited the oviposition of SBPH at the early stage of the treatment,the mixture of Jinggangmycin and Triazophos inhibited the reproduction of SBPH,and the expression of RPS2 and Vg decreased;In the treatment group of JT,injection of Jinggangmycin for 24 hours and then Triazophos for 24 hours could still inhibit the reproduction of SBPH,and the expression of RPS2 and Vg decreased;after control+dsRPS2,the number of eggs laid decreased,the preoviposition period and oviposition period prolonged,the female lifespan shortened,and the expression of RPS2 and Vg decreased.These results showed that the RPS2 played an important role in the reproduction of SBPH after the JC,JMT,JT treatment.