Ecological Adaptation And Pathogenic Bacteria Isolation,Identification And Pathogenic Mechanisms Of Agriphila Aeneociliella

Agriphila aeneociliella?Eversmann??Lepidoptera:Crambidae?was newly reported in China in 2010.Its larvae severely damage wheat in early spring and cause substantial economic losses in wheat crops.And it has been expanding year by year since its occurrence.In order to explore the bio-ecological adaptation mechanism of the outbreak of A.aeneociliella,at the same time,reduce the chemical pesticide application,and develop a new biological control technique to control the damage of A.aeneociliella,the life history data was analyzed using the age-stage two-sex life table.Here,the demography of A.aeneociliella has been studied.The developmental threshold and the effective accumulated temperature have been measured.We explore the different stages of A.aeneociliella larvae under different temperature conditions on the food preference.the pathogenic bacteria Serratia marcescens JY9 infected with A.aeneociliella larvae was isolated,characterized,and the toxicity of JY9on A.aeneociliella larvae was measured.Based on the RNA-seq sequencing technology,the pathogenic characteristics of the bacteria were analyzed,and the pathogenic mechanism of the strain was preliminarily revealed.The main results are as follows:1.A.aeneociliella can complete the entire generation development within 18-27?.With the increase of temperature,the larval development duration is significantly shortened.The larvae had six or seven instars,and the percentage of seven instars increased with the temperature raised from 18 to 27?.The development time from egg to adult was 147.26 days at 18?and 119.67 days at 25?,respectively.The highest preadult survival rate was 72.60%at 18?and the lowest survival rate was 34.9%at 27?.The largest mean fecundity was495.53 eggs per female at 25?.The highest intrinsic rate of increase,the largest finite rate of increase,and the shortest mean generation time were calculated at 23 or 25?.For six-instar larvae,the developmental threshold of the egg and the total larval stage,and the effective accumulated temperature were about 7.05,4.95?and 571.5 degree?days,while it was about7.61 and 5.06?,and 651.7 degree?days for seven-instar larvae.The results indicated that the optimum temperature for the growth and development of A.aeneociliella was between 23 and25?,and the adults could have the largest reproductive potential at 25?.When the temperature was 15?,the adults of A.aeneociliella could not reproduce normally.And if the temperature was higher than 32?,the development of the whole generation could not be completed.2.For newly hatched A.aeneociliella larvae,the proportion of select maize was larger than that of select wheat at 18,23 and 27?after 24 h incubation.And there were more newly hatched A.aeneociliella larvae select to eat wheat after 72 h incubation.This shows that the newly hatched A.aeneociliella larvae prefer to eat maize at the first 24 h,but switch to eat wheat after 72 h incubation,under circumstances of 18,23 and 27?.However,the feeding preference between wheat and maize of A.aeneociliella 5^6thh instar larvae was no significant difference.For the last-instar larvae,there was also no significant differences in the selection of pupation area between maize and wheat planting area.3.The pathogenic bacteria isolated from the larvae of A.aeneociliella were identified as S.marcescens JY9?CGMCC NO.15020?.S.marcescens JY9 has obviously pathogenic lethal effect on A.aeneociliella larvae.Toxicity of S.marcescens JY9 to A.aeneociliella larvae was assayed by means of contact infection.When the concentration of JY9 is 1.5×10⁹ cfu/mL,the corrected mortality rate of 3^rdd instar larvae of A.aeneociliella reached by 73.74%.And the median lethal concentration is LC₅₀=2.4×10⁹ cfu/mL.4.We have got about 59.7 Gb bases about 3^rdd instar larvae of A.aeneociliella in total on BGISEQ-500 sequencing platform.After assembling all samples together and filtering the abundance,we got 61238 Unigenes,the full length,average length,N50,and GC content of Unigenes were 88686507 bp,1448 bp,2576 bp and 40.7%respectively.And then annotated Unigenes by aligning with 7 functional databases,finally,30552?NR:49.89%?,16771?NT:27.39%?,21878?Swissprot:35.73%?,21528?KOG:35.15%?,23446?KEGG:38.29%?,2438?GO:3.98%?,and 22737?InterPro:37.13%?Unigenes were annotated.We detected 30316CDS by Transdecoder,5011 SSR distributed on 4235 Unigenes,and predicted 4642Transcription Factor?TF?coding Unigenes.5.The gene expression levels of 46 genes changed significantly after 24 h of 3^rdd instar larvae of A.aeneociliella infected with S.marcescens JY9 compared to the control,of which36 genes were up-regulated and 10 were down-regulated.After 48 h,the expression levels of170 genes were significantly changed,among them,44 were up-regulated and 126 were down-regulated..The signal transduction and metabolic pathways of A.aeneociliella were affected by being infected by S.marcescens.The DEG?Differentially Expressed Genes?that related to nucleotide metabolism and aging pathway was down regulated.We suggested that the lethal mechanism and the affection of development and reproduction to S.marcescens of JY9 could be as a result of altering the gene expression in longevity signaling pathway of DAF-9/DAF-12.