Analysis Of Rhizosphere Microorganisms Associated With Tobacco Fusarium Root Rot And Screening Of Biocontrol Microorganism

In recent years,Fusarium mycorrhizal rot of Tobacco has become one of the most serious root diseases in the main tobacco producing areas of our country,causing serious economic losses to tobacco production.The structure of rhizosphere microbial communities related to tobacco root rot was analyzed systematically,the influence of the interaction between tobacco and environmental microorganisms on tobacco root rot was analyzed,and the microorganisms with biological control value were screened,which is of great significance for green control of tobacco Fusarium mycorrhizal rot.In this study,the rhizosphere soils of diseased and healthy tobacco plants were collected in Xiang Cheng Xian,Henan Province.On the basis of isolation and identification of pathogenic Fusarium species,microbial community diversity and analysis screening of antagonistic organisms were carried out.The main results are as follows:(1)Two Fusarium species,Fusarium solani and Fusarium Oxysporum,were isolated and identified from the root tissues of diseased tobacco plants.incidence rate of tobacco infected by Fusarium solani and Fusarium Oxysporum reached 93.33% through indoor pot test on the 8th days and the disease index of them reached 36.67 and 40 respectively.Inoculation of Fusarium oxysporum was the fastest,with the incidence rate of 86.67% on the third days after inoculation.The maximum incidence rate(93.33%)was achieved after fivedays of inoculation,indicating that the pathogenicity of Fusarium oxysporum were stronger than that of Fusarium solani.Isolation and identification of the pathogenic Fusarium species of the sampled tobacco plants will lay a foundation for the next step of metagenomics analysis of rhizosphere soil.(2)The results showed that there were 22 phyla,305 genera and 23 phyla and 280 genera in rhizosphere soil bacteria of Fusarium mycorrhizal rot and healthy tobacco plants respectively.The diversity of bacterial structure between diseased and healthy tobacco plants was not different in population number,but in population structure and abundance.The change of rhizosphere fungi may be more closely related to root rot.The dominant bacteria in the top 5 of relative abundance were Actinobacteria、Proteobacteria、Firmicutes、Chloroflexi and Acidobacteria,and the top five dominant genera were Bacillus 、Blastococcus、Pseudoarthrobacter 、Nocardioides and Streptomyces.There were significant differences in relative abundance between diseased and healthy tobacco plants at the phyla classification level,including Actinobacteria、 Proteobacteria、 Firmicutes、Chloroflexi、 acidobacteria.the bacteria with significant difference in relative abundance at genus classification level were Bacillus、Blastococcus、Pseudoarthrobacter、 Nocardioides and Streptomyces.The existence of these different flora may affect the ability of plants to obtain nutrients from soil.(3)The metagenomic sequencing of Fusarium mycorrhizal fungi in rhizosphere of tobacco and healthy tobacco plants showed an average of 15 phyla,66 genera and 23 phyla,93 genera.The diversity of fungal structure between diseased and healthy tobacco plants in tobacco field was significantly different in population number,and there were significant differences in population structure and abundance.Among them,Ascomycota 、Basidiomycota、Mucoromycota、Mortierellomycota and Mlpidiomycota are the top 5 in relative abundance,Fusarium、Alternaria、Solicoccozyma、Mucor and Humicola are the top 5 dominant fungi.There were significant differences in relative abundance between diseased and healthy tobacco plants at the phylum classification level,including Ascomycota,Basidiomycota,Mucoromycota,Mortierellomycota,and Olpidiomycota.at the genus classification level,the significant difference in relative abundance are Fusarium、Alternaria、Solicoczyma、Mucor and Humicola.(4)A total of 788 rhizosphere soil fungi were isolated from diseased tobacco plants and healthy tobacco plants by plate separation method.The antagonistic fungi against Fusarium solani and Fusarium oxysporum were screened,and 118 strains of fungi with antagonistic effect against at least one Fusarium were screened,Fusarium solani 、Fusarium oxysporum、Fusarium proliferatum、Fusarium verticillioides and Fusarium equiseti were used as the target pathogenic fungi to screen 118 strains of antagonistic fungi,and five strains with antagonistic effect against five target Fusarium were screened out.After further morphological and molecular identification of these five strains,all of them are Trichoderma strigosum and Trichoderma hamatum.In this study,we analyzed the microbial structure in rhizosphere soil of Tobacco Infected by Fusarium,and the difference between the rhizosphere microbial community of the diseased plant and the healthy plant was clarified,which provided the basis for further elucidating the interaction mechanism of tobacco rhizosphere microorganism pathogenic Fusarium.Two Trichoderma strains with significant antagonistic effects against all five pathogenic Fusarium species were screened,which provided biocontrol resources for soil biological control of Fusarium root rot and had obvious application potential.