| Tobacco bacterial wilt is a soil borne bacterial disease of tobacco caused by R.solanacearum,which is seriously harmful and difficult to control.At present,the main control method is chemical control,which has a great impact on the environment.Therefore,it is of great significance to find a green and sustainable prevention and control technology.Biofumigation can effectively control pathogenic organisms in soil,improve soil fertility,improve soil physical and chemical properties and microbial community composition.It is a safe,pollution-free and sustainable soil borne disease control method.In this study,the biofumigating materials of tobacco bacterial wilt were screened,and the biofumigating conditions were optimized.The effects of biofumigating on soil physicochemical properties,enzyme activities,soil microbial diversity and community composition were explored.(1)The results showed that all the 17 fumigation materials had inhibitory effect on R.solanacearum,among which broccoli(Brassica oleracea L.var.italica Planch.)had the best inhibitory effect on tobacco bacterial wilt,and the inhibitory rate could reach 95.31%;rocket(Eruca sativa Mill.)had better inhibitory effect on tobacco bacterial wilt,and the inhibitory rate was 95.1%.(2)Optimization of biofumigation conditions.Taking broccoli as fumigation material,the results showed that the optimum amount of biofumigation material was 4%～6%,the optimum fumigation temperature was 26℃～32℃,the optimum soil water content was about 70%,and the optimum fumigation time was 14 d～21 d.Using rocket as fumigation material,the results showed that the optimum amount of biofumigation material was 4%～6%,the optimum fumigation temperature was 26℃～32℃,the optimum soil water content was about 70%,and the optimum fumigation time was 14 d～21 d.(3)Soil physical and chemical properties and soil enzyme activities were detected.The results showed that broccoli and rocket biofumigation treatment could improve the contents of total nitrogen,alkali hydrolyzable nitrogen and available potassium in soil.Compared with the control,the increase amounts were 5.9%～11.8%,39%～41.4% and 2.3%～3.5%,respectively.The conductivity value of soil was significantly increased by 37% and 78%,respectively.At the same time,broccoli biofumigation could improve soil urease activity,which increased by1.94% compared with the control,and rocket fumigation could significantly improve sucrase activity,which increased by 52.90% compared with the control.(4)16S rRNA and ITS sequencing technology were used to detect the effects of biofumigation on soil bacterial and fungal diversity and community composition.The results showed that broccoli treatment and rocket treatment increased the abundance of soil bacteria,and the species diversity of the two groups was greater than that of the control group.The composition of soil bacterial and fungal communities changed greatly after biofumigation,which was mainly manifested in the increase of relative abundances of Proteobacteria,Bacteroidetes,Chloroflexi,Firmicutes,Armatimonadetes and Candidatus＿Saccharibacteria at the phylum level,and the increase of relative abundances of chitinophagaceae,Planctomycetaceae and Anaerolineaceae at the family level after biofumigation of broccoli and rocket.The relative abundance of soil fungi at phylum level was significantly increased by Mortierellomycota,and the relative abundance of soil fungi at family level was significantly increased by Mortierellaceae and Microascaceae.By LEfSe analysis,Armatimonadetes,Methylphiles,Flavomonospora and Fungal Ascomycota,Pseudoeschia and Fungi may play an important role in the antagonistic or synergistic effect of biofumigation on R.solanacearum.(5)The pot experiment showed that broccoli and rocket biofumigation treatment could effectively reduce the number of R.solanacearum in soil,reduce the incidence rate and disease index of tobacco bacterial wilt,and control the tobacco bacterial wilt by 74.75% and 65.12%respectively. |
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