Effect Of Abscisic Acid Receptor Agonist AMF4 In Combination With Pymetrozine On The Control Of Nilaparvata Lugens

With the increasing of agricultural chemicals,it is crucial to use scientific and rational mixture to save usage and improve the efficiency of agricultural chemicals.Abscisic acid(ABA),one of the six major hormones found in plants,is used as a biochemical pesticide of plant origin,plays an important role in regulating plant resistance to abiotic stresses(drought,salinity,etc.)and biotic stresses(diseases,insects,etc.).However,the instability of ABA limits its application in agriculture,which prompted researchers to explore the use of ABA receptor agonists in plants.AMF4(ABA mimic 1 tetrafluoro derivative)is a fluorine derivative of ABA analog 1,exhibits higher stability and significantly enhances its binding affinity to PYL(pyrabatin riesistance 1-like)receptors compared to ABA.AMF4 is far superior to ABA in protecting plants from drought stress(abiotic stress),but the role of AMF4 in plant resistance to biotic stresses has not been reported.Pymetrozine is one of the insecticides commonly used to control Nilaparvata lugens.Due to overuse of pymetrozine in production,N.lugens has developed a certain degree of resistance to pymetrozine.This thesis proposes to carry out a combination of the ABA receptor agonist AMF4 and pymetrozine to screen out an optimal ratio and investigate its effect on N.lugens,as well as its effect on rice insect resistance,hormone and defence enzyme activity.The implementation of this experiment will benefit the green control of N.lugens in rice fields,solve the current increasingly serious problem of pest resistance and provide a better research direction for green control policy.The results of the study are as follows:1.Effect of AMF4 in combination with pymetrozine on N.lugens controlCompared with ABA,AMF4 showed higher toxicity against N.lugens,and 4.441 mg/L AMF4 treatment has the best effect.After feeding on rice treated by 4.441 mg/L AMF4,the mortality rate of N.lugens nymphs significantly increased by 21.24%,and the single-female egg production and egg hatchability of N.lugens respectively decreased by 60.41%and 43.97%.In the test of screening compounding,a significant synergistic effect was found at a 1:30 volume ratio of 10 μM AMF4 to LC50 concentration(17.927 mg/L)of pirimicarb,with a co-virulence factor of 26.68 and a co-toxicity factor of 143.87.Among three treatments,N.lugens feeding on rice in pymetrozine and AMF4 group had the greatest effect,and compared with the control,the survival rate of nymphs,single female egg production and egg hatchability were significantly reduced,by 48.96%,70.00%and 94.06%,respectively.It can be seen that the combination of AMF4 and pyraphidone has a synergistic effect on the control of N.lugens.2.Evaluation of rice resistance agaist insect pest after the treatment with the compound agentsThe feeding tendency test showed that the treatments of pymetrozine,AMF4,the combination of pymetrozine and AMF4 on rice were not conducive to the feeding selection of N.lugens.The plant selection rate of N.lugens in the compound treatment group reached the lowest at 24 h,which was 72.20%lower than the control group.Electrical penetration graph(EPG)showed that the feeding duration of N.lugens in phloem was significantly reduced,alleviating the damage of N.lugens to rice in the combination of pymetrozine and AMF4 group.The average injury scale and plant functional loss index of rice were also verified.Further study found that AMF4 treatment induced callose deposition in rice and improved resistance to N.lugens.3.Effect of compounded agent treatments on hormone content of rice and its defence responseThe HPLC-MS and PCR tests revealed that the compound agents regulated rice resistance N.lugens against through affecting ABA,JA and SA pathways and induced the expression of related genes.Rice defensive enzyme activity assays showed that rice antioxidant enzymes peroxidase(POD)and superoxide dismutase(SOD)played important roles in the defense process.This study provides a better research basis for green prevention and control technology to rice and other plant pests and diseases in production.