| Plutella xylostella is a worldwide pest with strong adaptability,wide spread and rapid reproduction,which mainly harms cruciferous vegetables.Plutella xylostella has serious overlap of generations and is increasingly resistant to chemical pesticides.Beauveria bassiana and its biological agents have the characteristics of wide insecticidal range,strong pathogenicity,harmless to human and livestock,and no ecological pollution.Therefore,it is very important to develop an ehigh-efficiency biological preparations of Beauveria bassiana for Plutella xylostella,and has received more and more attention.In this paper,a strain Bb2393 with high virulence to Plutella xylostella was screened from the strain library of Anhui Key Laboratory of Microbial Control,Anhui Agricultural University.The Spore production of the strain at different temperatures,the colony diameter on different carbon source SDAY medium and the biomass of SDY medium in different carbon sources were measured,which provided the basis for the laboratory culture of the strain;The insecticidal spectrum of the strain was measured to study the insecticidal universality of the strain.At the same time,in order to further understand the immune response mechanism of Plutella xylostella,Firstly,the best inoculation mode of the strain against diamondback moth was obtained by indoor bioassay,and then the virulence of the two strains of Beauveria bassiana was selected and verified by indoor bioassay.Finally,the transcriptome analysis of the two strains of Beauveria bassiana infecting P.xylostella for 24h was carried out by optimal vaccination method.Through comparative analysis,the difference of immune response genes in P.xylostella in response to different virulence Beauveria bassiana infections was obtained,which provided a theoretical basis for reducing the immunity of Plutella xylostella from the molecular biological point of view.The main results of this study are as follows:1.Screening of optimum temperature for sporulation of Bb2393 strainThe 1ml spore suspension(1×106/ml)was added to the spore-producing medium,Uniform coating.The spore production was measured after 12 days of incubation at 15,20,25,30 and 35 degrees Celsius respectively.the sporulation of Bb2393 was best at 25℃.2.Screening of optimum carbon source for liquid fermentation of Bb2393 strainThe 1 ml spore suspension(1 ×106 conidia/mL)was added to 200 ml of SDY liquid medium,and the dry weight of the hyphae was measured after shaking for 12 days on a shaker(25℃,220rpm).The 10 ul spore suspension(1×106 conidia/mL)was added to the center of the SDAY solid medium,and the growth diameter was measured on the 7th day and the 14th day,respectively.Finally,combined with the market price of different carbon sources,glucose is the best carbon source for Bb2393 liquid fermentation.3.Study on the insecticidal spectrum of Bb2393 strainThe infection effect of Bb2393 against silkworms,corn borer,tea ruler,tea aphid,whitefly through indoor bioassay.the results showed that Bb2393 had a wide range of infection and strong infection ability.4.Screening of the best inoculation method for the transcriptional group of Bb2393 strainThis paper compared the pathogenicity of Beauveria bassiana Bb2393 to Plutella xylostella under four different inoculation methods.The 1×107 conidia/mL concentration spore suspension was inoculated into the second instar larvae Plutella xylostella.The corrected mortality of Bb2393 under different inoculation methods show that the dip method is the best in the above four methods.5.Toxicity determination of Bb2393 strain and Bb2338 strain against Plutella xylostellaThrough indoor bioassay,the spore suspension at a concentration of 1×107 conidia/ml infects the second instar larvae,the corrected mortality rate of Bb2393 to Plutella xylostella is 82.76%,and the corrected mortality rate of Bb2338 to Plutella xylostella is 24.13%.6.Comparative analysis of differentially expressed genes in the immune response of Plutella xylostella to different virulence Beauveria bassiana infectionsComparative analysis of the genes expressed in the experimental group HIPX24 and the experimental group LIPX24 and the control group WTPX.In the WTPX-vs-HIPX24 group,1357 significant differentially expressed genes(FOR≤ 0.001,log2Ratio≥1)were obtained,and the GO secondary classification results showed that 1357 DEGs were classified into 39 GO terms,Pathway significance analysis,1357 DEGs can be compared to 307 different pathways,and 25 common insect immune genes were selected for comparative analysis.DEGs found that 16 immune genes were up-regulated;In the WTPX-vs-LIPX24 group,1947 significant differentially expressed genes(FOR≤0.001,log2Ratio≥1)were obtained,and the GO secondary classification results showed that 1947 DEGs were classified into 38 GO terms,Pathway significance analysis,1947 A DEGs can compare to 320 different pathways and select the same 25 common insect immune genes for comparative analysis.DEGs found that 21 insect immune genes were up-regulated. |
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