| Diaphorina citri is the only insect vector of citrus Huanglongbing and is an important citrus pest in the world.At present,chemical control of D.citri is still the main means to control the propagation of HLB,but the widespread use of chemical agents has increased the burden on the environment and the risk of insect resistance.Accurate delivery of chemical pesticides and RNAi pesticides by nano-delivery system to improve the efficiency and delay the development of pest resistance has become a current research hotspot.The ABC transporter protein of D.citri mediates its resistance to Cycloxaprid.On this basis,the pesticide loading system of nanomaterial loaded with dsRNA and Cycloxaprid was constructed and its synergistic efficacity was studied,which provided a theoretical basis for the research and application of nanotechnology in the field of new green pest control of D.citri.The main results are as follows:(1)Chitosan(Chitosan,CS)dsRNA loading system significantly improves the silencing efficiency of ABCH6 gene of D.citri.Electrophoresis results indicated that the optimal fusion ratio of CS/dsRNA-ABCH6 nanoparticles complexes is 1:1.The stability of CS/dsRNA-ABCH6 was determined by Ribonuclease A,and it was found that the CS nanoparticles could protect dsRNA from degradation by Ribonuclease A.When the concentration of dsRNA-ABCH6 was 200 ng/μL and the treatment time was 12,24 and 48 h,CS significantly improved the silencing efficiency of ABCH6 gene of D.citri,and the maximum silence efficiency was 62.66% after 48 h treatment.The pesticide sensitivity results after gene silencing showed that compared with the control group(dsRNAABCH6 alone),the CS dsRNA loading system significantly improved the insecticidal efficacy of Cycloxaprid,that is the mortality rate of D.citri in the treated group increased by 1.49-2.37 times under the same concentration(1.19 mg/L)of Cycloxaprid.(2)Five concentrations of 0.5,1.0,2.0,4.0 and 8.0 mg/L were used to check the insecticidal efficacy of Cycloxaprid(Cycloxaprid,Cyc),25%Cycloxaprid wettable powder(25% Cyc-WP)and the nano-hydrogel loaded with Cycloxaprid(Cyc@MPs).The results showed that the mortality rate of D.citri after treatment with Cyc@MPs was higher than that of Cyc and 25% Cyc-WP at five concentrations,the mortality rate of D.citri after 3 days of treatment at a concentration of 4 mg/L was 1.62 and2.42 times higher than that of Cyc and 25% Cyc-WP,respectively.The contact angle and surface tension of the Cyc@MPs,Cyc and 25% Cyc-WP were measured.It was found that the contact angle and surface tension of Cyc@MPs is smaller than Cyc and 25% Cyc-WP.In the verification experiments of resistance to ultraviolet degradation and rain erosion,it was found that the mortality rates of D.citri after 24 h Cyc@MPs treatment at a concentration of 50 mg/L and 1 h after UV irradiation were 1.40 and 2.30 times that of Cyc and 25% Cyc-WP,respectively.At a concentration of 50mg/L and a flow rate of 1.5 m L/min for 3 min,the 24 h mortality rate of Cyc@MPs was 1.58 and 1.89 times that of Cyc and 25% Cyc-WP,respectively.These results indicated that MPs has good anti-oxidation and anti-flushing effects on pesticide protection.(3)Metal organic framework(MOF)nanomaterials was synthesized by one-pot method.Cyc@MOF was synthesized by situ encapsulation method,the maximum dose loading rate was 27.02%±0.06%.Cyc@MOF was dispersed into CS working liquid containing dsRNA-ABCH6 with a concentration of 200 ng/μL.A gene and pesticide co-delivery system of nanomaterials was synthesized by high temperature incubation and electrostatic adsorption.The insecticidal performance of Cyc@MOF,dsRNA-ABCH6 alone loaded and dsRNA-ABCH6 and Cycloxaprid codeliveried by CS and MOF were compared at 6.93 mg/L.The mortality rate of the co-deliveried system after 48 h treatment was 2.13 times that of Cyc and 1.35 times that of Cyc@MOF,respectively.The results showed that the co-delivery system showed better advantage in pest control. |
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