The Changes Of Microbial Community In Tobacco Soil Infected With Soil-borne Disease And Its Influencing Factors

In this study,which aimed at the unclear changes of soil microbial community in tobacco soil infected with soil-borne disease(bacterial wilt)in Guizhou,experiment was set up in the low mountains and hills tobacco area in the southeast of Guizhou province(Tianzhu county,TZ for short below),the hilly and basin tobacco area in the middle of Guizhou province(Kaiyang county,KY for short below),and the plateau mountainous tobacco area in the west of Guizhou province(Weining county,WN for short below).With the Illumina-MiSeq sequencing technology,the difference of soil microbial community between diseased infecting area(D)and healthy area(H)were analyzed to clarify the spatial change of soil microbial community when soil-borne diseases occurred,and the impact of the occurrence of soil-borne disease on the change of soil microbial community structure.Furthermore,a pot experiment of biocontrol bacteria F11(B.amyloliquefaciens F11)was conducted to explore the F11 effect on the control of soil-borne diseases and its influence on microbial community.The main conclusions of this study are as follows:(1)The structure of soil microbial community in different tobacco soil-borne disease areas were generally the same,but their structural characteristics had obvious spatial variations.Sphingomonas and Gemmatimonas were the dominant genera in these climate regions,but the relative abundance of the two genera was quite different in each climate region.As the altitude increased,the relative abundance of Sphingomonas increased,the abundance of Gemmatimonas stabilized,and the genera with relative abundance greater than 1% in the dominant genera in soil-borne disease areas gradually decreased.(2)The occurrence of soil-borne diseases(bacterial wilt)would significantlychange the soil microbial community.The analysis of OTU and Alpha diversity index showed that compared with H,D microbial species were more abundant in low-altitude climatic areas(TZ),and species diversity was higher in high-altitude areas(WN).In terms of soil niche,Sphingomonas and Gemmatimonas were dominant genera for D and H in each climate zone,and the relative abundance of D was higher.As the altitude increases,the relative abundance gap between D and H became larger.Cluster analysis and PCoA analysis showed that the microbial community structure difference between D and H in the same climate zone was small,but the relative abundance of the dominant microbial genera of D and H in different climate zones differed greatly,and the relative abundance gap gradually increased as the altitude increases.The difference in relative abundance of the dominant genera D and H in WN region was the largest.(3)The higher the soil fertility and enzyme activity,the more likely it was to cause the occurrence of soil-borne diseases,which in turn changed the structure of soil microbial community.The 13 soil environmental factors such as soil pH,TN,TP,CEC,S-PA in different climate zones results showed that D was than H,and with the on-site disease situation in each climate area,the soil AN was preliminarily determined The increase of phosphatase and the decrease of SOM and sucrase were important factors to induce the outbreak of soil-borne diseases.Furthermore,the Redundancy Analysis(RDA)showed that the soil microbial community structure in the TZ disease area was greatly affected by TN,WN was mainly affected by TP,SOM and AN,and KY was mainly affected by pH and AK;while in D and H,DTZ.The soil bacterial communities of DWN and HWN were mainly affected of TN with HTZ.The soil bacterial communities of DWN and HWN were more affected by AN,TP,and SOM;while the spatial distance between DKY and HKY was relatively long,and HKY was affected by pH,TK,and AK.(4)The application of B.amyloliquefaciens F11 microbial agent could effectively control the bacterial wilt of tobacco plants.The application effect was best in the early stage of bacterial wilt,and it was better than conventional pesticide control.The composition and diversity index of rhizosphere soil microbial OTUindicated that the abundance and diversity of soil microbial community of treatment which applied F11 at the onset were tended to be similar to those of healthy soil(H),and the two indexes of the both two treatments was higher than other diseased soil treatments,which indicated that the application of F11 microbial agent in the early stage of diesease may be beneficial to the restoration of soil microbial ecology in soil-borne disease areas.Metallibacterium,Saccharibacteria genera incertae sedis and Ralstonia were the dominant bacterial genera in the treatment of diseased soil,but the relative abundance of dominant bacterial genera was inconsistent among the treatments.The abundance of Sphingomonas in H was low,while it was higher in the treatments of diseased soil.Among these treatments,the abundance of Sphingomonas was the lowest when F11 was applied in the early stage of disease.Combined with the biological control effect,the genus may be an indicative microbial flora of soil-borne disease.