Proteobacterial dominance in endophytic bacterial diversity in switchgrass growing under nitrogen range and effect on plant growth

AbstractSwitchgrass (Panicum virgatum L.) is native to North America and cultivated as a forage and bioenergy crop. Inorganic fertilizers enhance biomass production, increase production costs, and pollute the environment. Switchgrass cultivation using an eco-friendly approach might be achieved by inoculation with beneficial microbes. Therefore, the diversity of cultivable endophytic bacteria from roots and shoots of switchgrass growing under a nitrogen regime was studied. The potential of bacteria for plant growth promotion (PGP) was tested under in vitro conditions. A total of 216 bacterial isolates obtained belonged to four phyla and 33 genera, and most isolates were obtained from plants growing under no (0 kg/ha) or low nitrogen (90 kg/ha) input, rather than higher N (180 kg/ha). Higher numbers of isolates belonged to the phylum Proteobacteria, and genus-wise representation showed the dominance of Pseudomonas, Enterobacter, and rhizobia. Bacterial isolates were tested for PGP properties, e.g. phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, Indole Acetic Acid (IAA) production, and nitrogen fixation. Many isolates were positive for one or more PGP properties. In in vitro analysis, selected bacterial isolates were inoculated in two commercial switchgrass cultivars and a showed cultivar-specific response. PGP isolates can be used for pot or field trials and eventually for the sustainable cultivation of switchgrass.Keywords: Biofuel plantendophytesplant growth promotionnitrogen fixation Disclosure statementThe author declares no competing interests.Additional declarationsAs the author used plant material and this study does not report any animal or human research, ethics approval, consent to participate, and consent for publication are not required.Author contributionsThe author carried out all experiments, data analysis, and manuscript writing.Data availability statementThe raw data are available on request to the corresponding author. The bacterial strains are available from the Noble Research Institute, Ardmore, OK, USA.Additional informationFundingNoble Research Institute, Ardmore, OK, USA. This is the link of the institute (https://www.noble.org/).