The Effects And Mechanisms Of Raoultella Ornithinolytica Promotes The Growth Of Radish Seedlings And Influences The Feeding And Survival Of Plutella Xylostella

The Plutella xylostella(L.)has had a serious impact on the production and quality of cruciferous vegetables,and there is an urgent need to develop biological control techniques to control P.xylostella.In this paper,by analyzing the effects of different microorganisms on the growth of radish seedlings and the feeding and survival of P.xylostella,combined with microbial diversity and metabolomics to analyze the tertiary nutritional relationship of “microorganisms-radish seedlings-Plutella xylostella”,new biocontrol and growth-promoting bacteria were explored,and a theoretical basis was established for the development of microbial fertilizers.The main findings are as follows:1.Use the strains preserved in the laboratory to screen for bacteria with the ability to promote the growth of radish seedlings.Among the eight strains,Lysinibacillus sp.,Kocuria palustris,Carnobacterium gallinarum,Enterobacter ludwigii,Enterobacter sp.,Microbacterium arborescens,R.ornithinolytica and Enterobacter sp.can promote the growth of radish seedlings in the aboveground part.Except Enterococcus sp.,the remaining strains show significant inhibitory effect on the growth of radish root.Among them,R.ornithinolytica has the most significant effect on the growth of radish seedlings2.Analysis the effects of R.ornithinolytica on feeding and survival of P.xylostella.P.xylostella were fed with hydroponic radish leaves without R.ornithinolytica and with R.ornithinolytica.It is found that feeding P.xylostella with hydroponic radish leaves added to R.ornithinolytica could significantly promote P.xylostella feeding and reduce the 72 hours mortality and larval mortality of P.xylostella.In addition,soaking R.ornithinolytica on the surface of radish leaves will increase the weight growth rate of P.xylostella,but will not affect feed intake.It is indicated that R.ornithinolytica not only affects the growth of radish seedlings,but also may affect its material composition and content,which in turn affects the feeding and survival of P.xylostella,and the entry of the bacteria into the intestines of P.xylostella may help the host to carry out food transformation.3.In order to reveal the mechanism of microbial promotion of radish seedling growth and feeding and survival of P.xylostella,16 S r DNA high-throughput sequencing was performed on radish seeds endophytic bacteria,radish leaf bacteria and rhizosphere bacteria that hydroponics without R.ornithinolytica and with R.ornithinolytica.The results shows that R.ornithinolytica are detected only on the leaf surface and rhizosphere of radish hydroponic with R.ornithinolytica,and the abundance is low(leaf surface: 2.73%,rhizosphere: 0.31%).Whether or not adding R.ornithinolytica had little effect on the taxonomy of radish leaf and rhizobacteria at the phylum level,but had a significant difference on the community composition structure at the genus level.Indicating that after the addition of R.ornithinolytica,although the bacteria could not dominate in the population,it has a great influence on the composition of the group structure.Compared with the control group,the abundance of Rhizobium and Ensifer in radish leaves and rhizosphere cultured with R.ornithinolytica are significantly increasing,suggesting that these two bacteria may play an important role in promoting the growth of radish seedlings and changing the composition of secondary metabolites.In addition,the addition of R.ornithinolytica promotes the correlation between bacterial genus in the leaf and rhizosphere,but inhibites the correlation between bacteria on the leaf surface.4.Analysis of the effect of R.ornithinolytica on radish leaf met abolites by LC-MS non-targeted metabolism and the results showed that a total of 305 differential metabolites were screened for hydro ponic radish leaves between without R.ornithinolytica(group A)an d with R.ornithinolytica(group B).The KEGG pathway enrichmen t of differential metabolites in group A and group B are performed,and 305 differential metabolites are significantly enriched into 18 metabolic pathways,among which the enrichment of amino acid me tabolism pathway is more significant,and the addition of R.ornithi nolytica increases the nutrient content in radish leaves.5.Microbiome and metabolome association analysis show a significant correlation between microbes and differential metabolites.It is explained that R.ornithinolytica affects the bacterial community structure of radish leaves and rhizosphere,changes the composition of secondary metabolites of radish,increased the nutrients in radish leaves,reduces anti-insect active substances,promotes the growth of radish seedlings,promotes P.xylostella feeding and reduced P.xylostella mortality.This study combined with microbial diversity and metabolomics analysis revealed the tertiary nutritional relationship of "microbe-radish seedling-diamondback moth",which has important enlightening significance for the study of "insect-plant" interaction and evolution with microorganisms as a bridge,and also has important enlightenment value for the development and application of microbial fertilizers.