Studies On Intestinal Bacteria In Two Diamide Insecticide-Resistant Plutella Xylostella Strains And Screening Of Bacteria Degrading Flubendiamide

Plutella xylostella is one of the most serious pests in the production of cruciferous vegetables in the world because of its rapid development of resistance to synthetic insecticides and causing great losses in agricultural production.Studying its resistance mechanisms is essential for effective protection of beneficial insects,integrated pest management and the development of new insecticde.Recent studies have shown a potential link between insect gut microbes and insecticide resistance.There has been no research on the relationship between intestinal microbes and diamide insecticide resistance in Plutella xylostella although diamide as a kind of medicament which mainly works in the way of stomach action,the study of diamide insecticides' resistance mainly focuses on the mutagenesis of target,gene expression,detoxification enzyme activity.In this paper,we selected two diamide insecticides,chlorobenzamide and flubendiamide.The bacterial degradability and differences in community composition of susceptible strain chlorobenzamide resistant strain and flubendiamide resistant strain plutella xylostella larvae intestines were studied by traditional isolation and culture methods and high-throughput sequencing techniques.High performance liquid chromatography(HPLC)was used to screen the bacteriae which had the ability to degrade biamide insecticides.The main results are as follows:1.18 strains were obtained and cultured by traditional isolation,which belonging to Firmicutes,Proteobacteria and Actinobacteria.Firmicutes is the dominant bacteriae among all strains.Common bacterial species account for the largest proportion of the three strainsand and there are more quantitative than susceptible strains between the two resistant strains.2.38 OTUs were got from a total of 15 samples,It can be assigned to 7 phylums,mainly including Firmicutes,Proteobacteria,Actinobacteria,Cyanobacteria,Bacteroides.Enterobacter,Carnobacterium,Acinetobacter,Serratia,Staphylococcus,Enterococcus,Pseudomonas is dominant bacteriae in all strains.3.Two resistant strains showed more consistency population changes in gut bacteria than susceptible strains.There is no significant difference in the species of intestinal bacteriae between the resistant strains and susceptible strains,but there are differences in the abundance between two different strains.The diversity of bacterial population in susceptible strains was higher than that in resistant strains.The abundance of Proteobacteria in resistant strains is higher than that of susceptible strains,but The abundance of Firmicutes is lower.Enterobacter,Serratia,Bacillus,Anoxybacillus,Brebacillus,Rhizobium have higher quantity abundance in resistant strains,Carnobacterium,Staphylococci,Acinetobacter,Pseudomonas decreased,and there are significant differences with Enterobacter and Anoxybacillus between resistant strains and susceptible strains.Enterobacter accounted for 62.61% of the total bacteriae in susceptible strains,74.36% in chlorobenzamide-resistant strains and 73.65% in flubendiamide-resistant strains.Carnobacterium accounted for 24.70% of the total number of susceptible strains and 11.30% of chlorobenzamide-resistant strains accounted for 6.00% of flubendiamide-resistant strains.The increase of Enterobacter abundance and the decrease of Carnobacterium abundance are the main reasons for the change of Proteobacteria and Frimicutes.There was a stronger correlation among the resistant strains,and the 16 S rRNA function predicts a higher abundance in more functional pathways indicating that the resistant strains of intestinal bacteriae may have more functions.4.We verified its resistance and biodegradability of the insect-fluorophenyl amide by using the intestinal bacteria from the flubendiamide-resistant Plutella xylostella strain.The results showed Serratia liquefaciens,Enterobacter xiangfangensis,Bacillus pumilus,Carnobacterium maltaromaticum can grow in fenfluramide minimum salt-based medium.The mixed bacteria consisting of Enterobacter xiangfangensis,Enterococcus casseliflavus,Staphylococcus succinus,Bacillus pumilus,Serratia liquefaciens and Carnobacterium maltaromaticum shared biodegradation function to fipronilamide.This confirms that intestinal bacteria play a role in the insecticide resistan of Plutella xylostella.