Screening And Evaluation Of Biocontrol Fungi Metarhizium Pingshaense And Beauveria Bassiana On Nilaparvata Lugens St(?)l

Nilaparvata lugens Stal(Brown planthopper,BPH)belongs to the family Hemipteridae.It is one of the important field pests that harms rice in our country.By sucking the sap of rice,it causes yellowing or dead of rice,which serious threats to our food security.Our country prevention and control of brown planthopper is mainly based on chemical control.However,the use of long-term and unreasonable chemical pesticides seriously threatens the local ecological environment.At the same time,brown planthopper has developed resistance to various common insecticides,It leads to a decrease in effectiveness.Therefore,the search for new ways of biological control of the brown planthopper has become more important.In this paper,the strains that were lethal to the brown planthopper were collected and screened in the field.The strains were isolated,purified and cultured in the laboratory,and their species were identified.Two strains of Metarhizium pingshaense NJMP2103 and Beauveria bassiana NJBb2101 were obtained.The entomopathogenic fungi of the brown plant hopper play a deadly role,and further explored the factors that promote conidial germination of the M.anisopliae and the sublethal effects of Beauveria bassiana on the growth,development and reproduction of the brown planthopper.The prevention and control of brown planthoppers provides a new biological control strategy.1.Screening and virulence of high virulent strains of the brown planthopperThe brown planthopper collected from the field and infected with entomopathogenic fungi was isolated,purified,and cultured.The ITS sequence of the fungal ribosomal DNA was determined.The results were compared on NCBI,and the two strains of NJMP2103 and NJBb2101 were obtained.Through the Metarhizium pingshaense NJMP2103 indoor toxicity measurement,the concentration of 1×106 spores/mL calibration in six days the cumulative mortality of 60.0%In a short period of time,the M.anisopliae NJMP2103 can exert a good control effect on the brown planthopper.The indoor virulence test of Beauveria bassiana NJBb2101 against brown planthopper showed that brown planthopper gradually began to die on the fourth day and reached the highest cumulative corrected mortality rate by 68.7%on the tenth day.The acquisition of two fungal strains provides excellent materials for in-depth study of pathogenicity of strains and screening for appropriate biological control.2.The exploration of the factors that promote the germination of the conidia.Metarhizium anisopliae is an important entomopathogenic fungus.When infecting host insects,the germination rate of conidia of Metarhizium anisopliae on insect body surface affects the pathogenicity of pathogenic fungi to insects.This study relied on the laboratory screening of the strains of Metarhizium pingshaense NJMP2103.the experiment found that the germination rate of conidia of M.anisopliae in insect wings was much greater than that under normal conditions,By comparison with different concentrations of peptone solution,it was found that the germination rate in the wings infusion was significantly increased.Therefore,the germination rate of the conidia of Metarhizium anisopliae in different liquids was further explored.The experimental results showed that the components were more complex nutrient solutions(amino acids,Vitamins,sugars),the germination rate and sporulation of the conidia of Metarhizium anisopliae will be faster and more,and the appressorium will not be easily produced in the solution of high nutrient substances,but the metabolites of the M.anisopliae in the wing infusion treatment group Conidial germination is rapid,and the end of the sprout tube will expand,making it easier to produce appressorium.Therefore,a more in-depth study of the germination of the entomopathogenic fungi of the entomopathogenic fungi and the formation of appressorium are important for understanding the mechanisms of infection by entomopathogenic fungi,enhancing the sporulation and virulence of entomopathogenic fungi through external means,The biological control technology has very important significance.3.The effect of Beauveria bassiana on the growth and reproduction of the brown planthopperAt present,Beauveria bassiana as a microbial pesticide is widely used in field biological control.However,the sublethal effect of Beauveria bassiana on the brown planthopper is still unclear.This article used laboratory-selected Beauveria bassiana strain NJBb2101.A sub-lethal concentration of Beauveria bassiana NJBb2101 conidium suspension(5×105 conidia/mL)was inoculated into the third-instar nymph of N.lugens and was found to significantly reduce the survival rate of the nymph and the female ratio.Compared with the group,the N.lugens nymph of the treated group had a reduced probability of becoming an adult.At the same time,the brown planthopper infected by B.bassiana NJBb2101 also reduced the fertility of the parent,its mating rate,fecundity and hatching rate were lower than the control group,followed by three test insecticides(imidacloprid,Chlorpyrifos,Etofenprox)was used to treat female brown planthopper females,fourth-instar offspring nymphs and adult offspring females.It was found that brown planthoppers treated with sub-lethal concentrations of NJBb2101 Beauveria bassiana were more susceptible to these three agents and improved the sensitivity of chemical pesticides.Therefore,a more in-depth study of the sublethal effects of entomopathogenic fungi should be used to combine entomopathogenic fungi with chemical insecticides for the combined control of rice pests such as brown planthoppers.