| Tobacco bacterial wilt disease is a plant disease caused by R.Solanacearum in which tobacco roots,stems and leaves are infested,causing huge economic losses every year.At present,tobacco wilt is mainly controlled by comprehensive treatment and spraying of chemical pesticides.Although these chemical control methods have certain effects,there are pesticide residue problems,which affect human health.Myxococcus sp.BS is a strain isolated from our school that has a broad-spectrum resistance to plant pathogens and has a good predatory effect on Ralstonia solanacearum.In this study,the slime bacteria BS was prepared as a microbial bacterial fertilizer to study its biocontrol effect on tobacco bacterial wilt and its rhizosphere microbial regulation mechanism.The main research contents and conclusions are as follows:1)Optimized the liquid fermentation conditions of slime bacteria BS.The single factor result is:the best carbon source is starch,the best addition ratio is 0.8%,the best nitrogen source is beef paste,the best addition ratio is 1.0%,the best inorganic salt is MgCl2,and the best addition ratio It is 0.1%,the optimal culture temperature is 32℃,the optimal initial pH of the medium is 7.4,the optimal rotational speed is 150 r/min,the optimal liquid v0lume is 50 mL.,and the optimal inoculation volume is 5%.Through the PB experiment the four factors that have the most significant influence on the dry weight of mycelia in the BS fermentation broth of the slime bacteria are obtained.Through the BBD experiment,the linear regression relationship between the interaction of four significant influencing factors and the dry weight of the fermentation broth was obtained,and the response surface curve was obtained.The results showed that when the inoculation amount was 4.80%,the pH value was 7.41,the temperature was 3 1.01℃,and the rotation speed was 154.73 r/min,the maximum dry weight of the cells was 0.1791 g/100mL.2)The effect of mycobacteria BS on the pot experiment of tobacco bacterial wilt.There are 5 treatment groups including clean water treatment,slime bacteria+Ralstonia mixed addition treatment,slime bacteria+ Ralstonia successive addition treatment,agricultural streptomycin+Ralstonia simultaneously addition treatment and Ralstonia solanacearum addition treatment group.There was no tobacco plant disease in the treatment group with the addition of Ralstonia solanacearum.The incidence rate of the agricultural streptomycin+Ralstonia addition treatment group was 20%,and that of the Ralstonia alone addition group was 100%.The measured values of the slime bacteria+Ralstonia solanacearum addition treatment group and the slime bacteria+Ralstonia addition treatment group on the tobacco leaf moisture content,leaf SPAD value,plant dry weight and agronomic traits in the tobacco industry assessment specifications are all excellent.The treatment group was added simultaneously to streptomycin+Ralstonia solanacearum,and was significantly better than the Ralstonia alone.Tobacco leaf SOD,POD and CAT three kinds of resistance enzyme activity measured values showed a consistent trend,myxobacteria and Ralstonia added group<streptomycin and Ralstonia simultaneously added group<Ralstonia alone added group.The activities of the three stress-resistant enzymes did not show a specific pattern in the roots.It can be seen that myxobacteria have a good control effect on tobacco bacterial wilt under pot experiment conditions,and the effect is stronger than agricultural streptomycin.3)The effect of mycobacteria BS on tobacco bacterial wilt in field trials.The R.solanacearum in the rhizosphere soil of each treatment group was quantified by fluorescence.The copy number of R.solanacearum was closely related to the incidence rate.In the treatment group with high incidence rate,the copy number of R.solanacearum was higher.The incidence of tobacco in all myxobacteria-added groups was less than the control group(CK),deep groove group(DG)and sparse plant group(SP),and except for the BS2+2 group,it was significantly less than the control group(CK)(P<0.05).It can be seen that the slime bacteria BS still has a very good control effect on tobacco bacterial wilt under field trials.4)The regulation mechanism of myxobacteria on the microbial community structure of tobacco rhizosphere soil.High-throughput sequencing results show that myxobacteria can significantly increase the abundance of dominant bacterial genus,the sum of TOP 10 bacterial genus abundance is manifested as deep groove treatment(DG)<sparse plant treatment(SP)<bacterial fertilizer addition(BF)<Bacterial agent addition(BS)showed an opposite trend to the incidence rate,especially the abundance of Stenotrophomonas in BS treatment group was significantly higher than that in other treatment groups.Analysis of the fungus genus showed that the abundance of Cladosporium in the BF and BS treatment groups was significantly higher than that in the other treatment groups.The Lefse analysis result of the bacterial community structure was obtained with the preset LDA score of 3.5.The bacterial agent addition(BS)treatment had 15 bacterial biomaker,which was the most in all treatment groups,while the control group(CK)and deep groove treatment(DG),Sparse plant treatment(SP)and bacterial fertilizer addition(BF),the number of bacterial biomaker is 3,2,5 and 3,respectively.The results of fungal lefse analysis showed that there were 10 fungus biomaker in BS treatment,while the number of bacterial biomaker treated by CK,DG,SP and BF were 4,4,6 and 6,respectively.Bacterial microbial community structure analysis showed that the BS and BF treatment groups can be well distinguished from other treatment groups and have large differences;PCA results and function predictions of bacterial function show that BS is clearly distinguished from other treatment groups in function There are significant differences between the above and other groups.The fungal community structure,functional PCA analysis and functional prediction analysis showed that the treatment group of bacterial fertilizer addition(BF)and bacterial agent addition(BS)were significantly different from the other groups in fungal community composition and function.In summary,Myxococcus sp.BS has a good biocontrol effect on tobacco bacterial wilt.Mycobacteria can improve the microbial metabolic function of rhizosphere soil by increasing the abundance of dominant microorganisms and adjusting the structure of soil microbial community.Tobacco resistance to bacterial wilt. |
