Screening Of Two Bacillus Strains And Their Control On Tomato Bacterial Wilt And Banana Wilt Disease

The soil-borne diseases of crops are difficult to prevent and cure,the variety of pathogenic bacteria is very diverse and the scope of infection is wide.Plants that have been seriously infected always resulted in death of the plants and caused major economic losses for agricultural production.In this study,for the purpose of biological control the crop soil-borne diseases,strains IC6 and IC11 which inhibited a variety of soil-borne pathogens were screened out from the soil of plant rhizosphere.Ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS)was used to identify the metabolites of the fermentation broth.Pot experiments were carried out to determine the control effects on tomato bacterial wilt and banana fusarium wilt.The main contents are as follows:(1)6 strains with strong antagonistic ability were isolated from the rhizosphere soil of tomato,eggplant,pepper and banana.Through physiological and biochemical analysis and 16 S rRNA sequence identification.The bacterial strains IC1,IC2,IC3,IC10 and IC11 were initially identified as Bacillus amyloliquefaciens,IC6 was Bacillus methylotrophicus.(2)The strains IC6 and IC11 have strong inhibitory effects on various pathogenic bacteria.The antibacterial diameters of R.solanacearum reached 20.99 mm and 24.05 mm,respectively,after incubation at 30� C.for 24 h using the spot-on-lawn assay.And the antibacterial diameter of the F.oxysporum f.sp.cubense were up to 14.90 mm and 22.64 mm,respectively.The total DNA extracted from the strain was used as a template to amplify multiple lipopeptide antibiotic gene fragments such as ituA,ituB,ituC,ituD,srfAA,srfAB,fenD,bamC and yndJ,and one more sboA gene was detected in strian IC11.The organic solvent methanol extraction 30 �C shake flask culture 24 h strain fermentation product,can inhibit the growth of pathogens.UPLC-MS analysis showed that the isoforms of Iturin,Fengycin and Surfactin homologues were detected in methanol extracts,which means that strains IC6 and IC11 have the ability to produce lipopeptide antibiotics.(3)The strains IC6 and IC11 both have strong ability to move and produce biofilm.On LBGM plates with 0.3% and 0.7% agar at 30�C,IC11 can grow over the entire plate more quickly;at 30�C Both liquid and 1.5% agar LBGM medium can produce a large number of biofilms.As the culture time increases,the membrane morphology between different strains is significantly different.(4)The tomato pot test results showed that the strains IC6 and IC11 could significantly reduce the incidence of tomato bacterial wilt.Treatment group IC6 biocontrol rates were 48.59%,respectively;while the data of IC11 were 57.78%.After 10 days of microbial agents treatment with tomato,the control FZB42 had a biocontrol rate of 50.47%,the biocontrol efficiency of IC6 and IC11 against tomato bacterial wilt reached 46.73%,58.88%.(5)The results of banana pot experiment showed that the biological control rates of the two agents against Fusarium of banana were 55.10% and 62.25%,respectively.It was proved that the strains IC6 and IC11 also had high-efficiency biological control effect on banana wilt disease.In summary,the results of the study show that strains IC6 and IC11 have great potential for biological control of soil-borne diseases,which can effectively reduce the incidence of tomato bacterial wilt and banana fusarium wilt,and can significantly inhibit the growth of many pathogenic fungi.At the same time,the identification of the metabolites and the evaluation of the biocontrol effect of Bacillus vanilla were also provided,which provided the dominant strain resources for the development and application of composite biofunctional biocontrol agents.