Evaluation of Physiological Traits Expressed in vitro and Effects on Plant Growth by Bacillus Endophytes

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Galloway, Jewel
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University Honors College Middle Tennessee State University
Bacillus species are an important group of rhizobacteria that have been shown to enhance the growth of plants and protect against diseases caused by plant pathogens. This study investigated the mechanisms used by B. atrophaeus and B. thuringiensis to promote plant growth and explored their potential as biofertilizers and biocontrol agents for application in agriculture. Effects of each bacterial strain on the growth of Brassica rapa were evaluated under greenhouse conditions with sterile soil. Plant growth promotion traits including nitrogen fixation, phosphate solubilization, and siderophore production were assessed using in vitro microbiological techniques. Additionally, in vitro methods were used to evaluate antagonistic activities against two soil-borne pathogens, Fusarium oxysporum and Agrobacterium tumefaciens. To verify nitrogen fixation activity, the nitrogenase gene, nifH, was amplified by PCR. Plants inoculated with B. atrophaeus had significantly greater biomass and increased length compared to the control. In the in vitro assays, B. atrophaeus exhibited antimicrobial and nitrogen fixation activity while B. thuringiensis was positive for siderophore production. These bacteria could potentially be used as biofertilizers and biocontrol agents in conjunction with currently used agrochemicals to reduce the environmental costs associated with synthetic chemicals.
College of Basic and Applied Sciences, Plant growth-promoting rhizobacteria, Bacillus, Brassica rapa