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Metabolomics approach to elucidate the mechanisms underlying biological control of Fusarium root rot by PGPR

Anthony Adesemoye: University of Nebraska Lincoln

<div>Plant growth promoting rhizobacteria (PGPR) have been used to control plant pathogens and enhance growth. The mechanisms used by many PGPR strains are unclear. A better understanding of the mechanisms could help improve efficacy. Fusarium root rot is a major soilborne pathogen of economic importance in row crops. <em>F. graminearum</em> and <em>F. oxysporum</em> are the two most important species causing Fusarium root rot in Nebraska. Chemical control is the most widely used method in controlling Fusarium root rot pathogens. Biological control, if understood, could be an important component of an effective integrated pest management system. <em>Burkholderia ambifara</em> C628 and <em>Bacillus simplex</em> R180, are PGPR strains with effective biological control against Fusarium root rot. The objectives of this research were to (1) extract, purify, and characterize the secondary metabolites secreted by <em>Burkholderia ambifara</em> C628 and <em>Bacillus simplex</em> R180 and (2) determine the role of the identified secondary metabolites in the biological control activities. These two PGPR strains were screened for lipopeptide antibiotic genes fengycin, bacillomycin, surfactin, iturin, and zwittermicin using PCR primers specific to the genes. Strain C628 showed the presence of only iturin A gene while R180 showed the presence of surfactin, bacillomycin D, and iturin A genes. These metabolites were extracted by acid precipitation from liquid cultures. The cell-free metabolite and crude extract showed antifungal bioactivity against pathogenic strains <em>F. graminearum</em> and <em>F. oxysporum</em>. The extract is being characterized by chemical analysis through high performance liquid chromatography-mass spectrometry.</div>