Rhizospheric bacteria from pristine grassland have beneficial traits for plant growth promotion in maize (Zea mays L.)

Abstract An emerging strategy in the sustainable production of staple crops such as maize is the use of plant growth-promoting rhizobacteria (PGPR) as inoculants. This study reports the screening and characterization of several rhizobacteria isolated from rhizosphere of pristine grassland in South Africa. The rhizobacteria were screened for their ability to exhibit important plant growth-promoting traits in vitro and under glasshouse conditions on a maize plant. In total, 98 isolates were initially characterized based on their colony morphology on different growth media of which 13 isolates tested positive for the production of siderophores and indole-3- acetic acid (IAA), whereas eight isolates solubilized inorganic phosphate. Screening for growth promotion experiment revealed that the PGPR isolates significantly (P ≤ 0.05) increased plant biomass, root length, and chlorophyll content index (CCI) when compared to uninoculated (control) plants. The best performing isolates were identified using 16S ribosomal RNA sequencing with additional characterization by DNA recombinase (recA) gene analysis. The 16S analysis indicated the effective rhizobial isolates are closely related to bacteria belonging to Pseudomonas, Burkholderia and Bacillus spp. at ≥98% nucleotide similarity and one isolate identified as Enterobacter sp. Most of these isolates exhibited multiple PGPR traits and resulted in enhanced growth of maize under glasshouse condition. The data generated provide vital information for use in the development of PGPR inoculants as alternatives to artificial chemical inputs in the cultivation of maize and possibly other crops.