Utilizing Rhizospheric and Bacterial Endophytes for Use as Potential Bio-fertilizers for Sustainable Agricultural Production

Brassica carinata crop production offers an exciting alternative approach to the energy crisis when looking at novel ways to power our motor vehicles. Bacterial endophytes, while residing in host-plant tissues, offer a wide array of plant growth promotion benefits such as nitrogen fixation to impart nitrogen (N) nutrition, phosphate (P) solubilization to make soil-bound phosphate more mobile in soil for plant uptake, can suppress pathogenic microbes such as fungus and produce plant growth hormones to offset stress incurred by the plant. Previous literature has shown that there is large interest in studying endophytes from economically important crops such as wheat, soybean, and corn. However, there is hardly any research being performed on oilseed crops such as Brassica carinata (Ethiopian mustard) and how endophytes from these plants could be used in agricultural management practices and as bio-fertilizers. We isolated and screen 20 endophytic bacteria from surface sterilized B. carinata plant tissue and screened these bacterial isolates for nitrogen fixation, phosphate solubilization, indole-3- acetic acid (IAA) production and fungal pathogen suppression. These bacteria to plants in an in-vitro setting, greenhouse and field setting to ascertain if there were any growth promotion capabilities in-planta. We found that the isolates all could all fix nitrogen and had various fungal suppression abilities depending on the pathogen. Three of the isolates could solubilize phosphate and nine could produce IAA. Greenhouse testing and field testing with different varieties of soybean, corn and wheat all showed varying results that could be due to host specificity, the native microbial communities and a genotype effect but did show growth promotion in certain cases. We also characterized four novel rhizosphere bacteria under the family Oxalobacteraceae. Using 16S rRNA, whole genome sequencing and biochemical profiling, we determined that these bacteria were all novel species and type stains and assigned them as the following: Duganella callidus DN04, Massilia arenosa MC02, Massilia hortus ONC3 and Noviherbaspirillum sperare M1. These results shed light on the potential of these isolates to be produced as a bio-fertilizers. However, more work needs to be performed to understand the plant-host relationship and how this might affect plant growth