| Chemical pesticides are highly toxic and pollute the environment,which have potential harm to human and animal he alth.As people pay more and more attention to environmental issues,highly active biocontrol agents are gradually applied.In the previous study,the research team isolated and selected two biocontrol bacteria with significant control effect on plant para sitic nematodes and soybean root rot from field soil:Chromobacterium violaceum ZS-1 and Enterobacter sp.CG-7.In this experiment,the field application effects of strains ZS-1 and CG-7 were evaluated,the colonization ability of streptomycin labeled strains was determined,and the soil microbial community structure and diversity after applying ZS-1 and CG-7 were sequenced by Illumina Miseq high-throughput sequencing platform to investigate their effects on soil microbial flora,in order to reveal the appl ication effect and potential mechanism of ZS-1 and CG-7.The main results are as follows:1.The evaluation of the application effect of strain ZS-1 and CG-7 on soybean showed that the control effect of strain ZS-1 fermentation broth diluted2 times on root rot caused by Fusarium oxysporum and Phytophthora sojae was33.5%and 22.7,respectively,and that of strain CG-7 fermentation broth diluted5 times was 34.5%and 25.3%,respectively.The field growth promotion experiment showed that the chlorophyll cont ent,weight per plant,number of pods per plant and pod weight per plant of soybean treated with ZS-1 and CG-7fermentation broth were higher than those of the control treatment.The growth promoting effect of fermentation broth spraying treatment was bett er than that of seed dressing treatment,and there was no significant difference between single bacterial solution application and mixed bacterial solution application.The evaluation of the application effect of strains ZS-1 and CG-7 on rice showed that the plant height,fresh weight and stem base width of rice treated with the fermentation broth of strain ZS-1 and CG-7 were higher than those of the control at seedling stage,and the chlorophyll content of rice from heading stage to yellow ripening stage w as significantly increased.There was no significant difference between single bacterial solution application and mixed bacterial solution application.The control effects of ZS-1,CG-7 and ZS1+CG-7fermentation broth on Heterodera elachista were 22%,71%and 46%,respectively,and the average yield increased by 12.2%～15.9%compared with the control.2.The resistant strain resistant to 300μg/m L streptomycin was obtained by using the medium containing streptomycin.The resistant strain had stable heredity,its growth curve was basically the same as that of the original strain,and had obvious antagonistic effect against Phytophthora sojae.At the same time,it had significant contact effect on H.elachista and Meloidogyne graminicola.The results of colonization of resistant strains in soil showed that strains ZS-1 and CG-7 could colonize effectively in soybean rhizosphere soil for a long time,and the content of strains reached the peak in rhizosphere soil10 days after inoculation,and the content of strains decreased gradually when ZS-1:3.2×10~7CFU/g,CG-7:5.4×10~7CFU/g,respectively.After 60 days of inoculation,the content in rhizosphere soil was ZS-1:1.2×10~4CFU/g,CG-7:4.4×10~4CFU/g respectively.Strain CG-7 could colonize effectively in rice rhizosphere soil for a long time,and reached the peak in rhizosphere soil 20days after inoculation.After 4.2×10~4CFU/g,the content of strain ZS-1 decreased gradually in rhizosphere soil,and decreased to 3.3×10~3CFU/g.Strain ZS-1 could not be colonized in rhizosphere soil of rice.3.The experimental results of the effects of strains ZS-1 and CG-7 on the soybean rhizosphere soil microbial flor a showed that the strains ZS-1 and CG-7treated soybean rhizosphere soil microorganism Alpha diversity index was significantly different from the control.The treatment of strains ZS-1 and CG-7increased the relative abundance of bacterial Proteobacteria,Chioroflexi and fungal Basidiomycota in soybean rhizosphere soil microbial community,and decreased the relative abundance of bacterial Planctomycetes,Verrucomicrobia and fungal Chlorophyta.The experimental results of the effect of strain CG-7on the rice rhizosphere soil microbial flora showed that the Alpha diversity index of soil microorganisms treated by strain CG-7 was significantly different from the control.The treatment of strain CG-7 increased the relative abundance of bacterial Acidobacteria and fungal Chioroflexi in rice rhizosphere soil microbial community,and decreased the relative abundance of bacterial Firmicutes and fungal Ascomycota in rice rhizosphere soil microbial community. |
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