STRAIN IMPROVEMENT OF BACILLUS VELEZENSIS BY TRADITIONAL TECHNIQUES TO CONTROL PLANT PATHOGENS

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dc.contributor.advisorMeena, Khem Raj
dc.contributor.authorRehman, Syed Vahida
dc.date.accessioned2023-10-16T16:08:32Z
dc.date.available2023-10-16T16:08:32Z
dc.date.issued2021
dc.description.abstractMicrobial Biological Control Agents (MBCAs) are used to biologically control plant diseases in crops. The first step towards developing an efficient biological control is to identify effective antagonistic strains. Molecular approaches can be used to improve the ability of wild type strains to reduce disease severity and disease incidence of plants. Random mutagenesis induced by physical mutagens like UV, X-rays, and gamma radiation, as well as chemical mutagens like ethyl methane sulfonate have been used to modify organisms genetically. To improve the antagonistic nature of Bacillus velezensis a gram positive, endospore forming, biosurfactant producing bacterium, random mutagenesis has been used. A total 11 mutants were obtained when subjected to UV irradiation and ethyl methane sulfonate for different time intervals on the basis of random morphological characters. Out of all these mutants, 7 mutated isolates have shown biosurfactant production when screened through emulsification activity. The highest emulsification activity against hydrocarbons, benzene and toluene was shown in Luria Bertani broth media of 85.67±0.21 against benzene 85.88±0.20 against toluene. The crude yield of biosurfactant produced by mutants was also improved after mutagenesis. The highest yield of crude biosurfactant of 0.361±0.001 was shown by mutant M3 and followed by mutant M5 of crude biosurfactant yield was 0.332±0.002 Growth profile of all the mutants along with unmutated culture was studied. Some mutants (M3, M7, M9) had took nearly ~36 h to reach stationary phase as the cultures had taken much time in lag phase. The total protein content of all the strains were also analyzed. The highest protein content of 80.88μg was shown by mutant M3 followed by 77.74μg by mutant M5. All the mutants were screened for antagonistic activity against the selected plant pathogens Helminthosporium maydis and Fusarium oxysporum f.sp. lycopersici by dual culture plate technique. 7 mutants have shown nearly 60-80% inhibition against both the pathogens. Crude biosurfactant produced by the cultures were used to screen the pathogens with improved antagonistic activity. Six mutants M3, M4, M5, M6, M7, M9 were shown the improved antifungal activity against the selected pathogens. The highest antagonistic activity of 81.69 % and 83.33 % was shown by mutant M3 against Fusarium oxysporum f.sp. lycopersici and Helminthosporium maydis. These six mutants were selected further to check the biocontrol ability against the selected pathogens through pot experiment. Separate pot experiment was conducted to check the biocontrol ability against Fusarium oxysporum f.sp. lycopersici in tomato crop and Helminthosporium maydis in maize crop. The results obtained has showed the significant increase in growth of shoot length, shoot fresh and dry weight, root length, root fresh and dry weight of maize and tomato crop. It was observed that M3, M5, M7, M9 has shown the maximum enhanced growth parameters than unmutated strain in both maize and tomato crop. The disease severity index and disease incidence were calculated against southern corn leaf blight disease and fusarium wilt disease respectively. Results obtained were shown that M3, M5, M7, M9 has significantly reduced the disease severity in maize crop and mutants M3, M5, M9 has significantly reduced the disease incidence from 65.5 % in control to 29.7%, 32.4%, 33.1% respectively. The present study has been isolated the mutants with improved antagonistic activities could be used as potential biocontrol agents.
dc.identifier.otherM/MICRO/448/2019-20
dc.identifier.urihttps://krishikosh.egranth.ac.in/handle/1/5810198987
dc.keywordsStrain improvement
dc.keywordsBacillus velezensis
dc.keywordstraditional techniques
dc.keywordscontrol plant pathogens
dc.language.isoEnglish
dc.pages74+i-x (Bibliography)
dc.publisherDr.RPCAU, Pusa
dc.subMicrobiology
dc.themeStrain improvement of Bacillus velezensis by traditional techniques to control plant pathogens.
dc.these.typeM.Sc
dc.titleSTRAIN IMPROVEMENT OF BACILLUS VELEZENSIS BY TRADITIONAL TECHNIQUES TO CONTROL PLANT PATHOGENS
dc.typeThesis
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