Elucidating key plant growth-promoting (PGPR) traits in Burkholderia sp. Nafp2/4-1b (=SARCC-3049) using gnotobiotic assays and whole-genome-sequence analysis.

Burkholderia sp. Nafp2/4-1b (=SARCC-3049) is a plant growth-promoting rhizobacteria (PGPR) initially isolated from the rhizosphere of pristine grassland in South Africa, and its ability to enhance growth was previously evaluated on maize (Zea mays L.). Here, the bacterium was tested with the aim of investigating its role in improving the nodulation and growth of the forage legume lucerne (Medicago sativa L.) when it is co-inoculated with the rhizobial symbionts of this legume in the glasshouse. When the co-inoculation resulted in a statistically significant (P = 0·05) increase in the number of nodules and improved plant biomass compared with single inoculation, we sequenced and analysed its genome to gain a better understanding of the genetic determinants responsible for the observed PGPR traits. The Illumina HiSeq 2500-sequenced genome resulted in 92 scaffolds, with an N50 of 322 407 bp, a total draft genome size of 7 788 045 bp and GC content of 66·2%. Analysis of the genome sequence confirmed the presence of a number of essential genes that code for various PGPR traits. The main plant beneficial genes associated with PGPR traits in Burkholderia sp. Nafp2/4-1b include pyoverdine siderophores biosynthesis gene (PvdF); acdS that codes for 1-aminocyclopropane-1-carboxylate (ACC) deaminase; the tryptophan synthase genes involved in auxin biosynthesis (TSA1, TSB1) and the pqqABCDE operon related to phosphate solubilization. This study generated valuable information on the potential of the PGPR Burkholderia sp. strain Nafp2/4-1b as an effective commercial inoculant, which warrants further formulation and field application studies before developing it into a low cost, environmentally safe and effective biofertilizer.

The Draft Genome Sequence of Burkholderia sp. Strain Nafp2/4-1b Confirms Its Ability To Produce the Plant Growth-Promoting Traits Pyoverdine Siderophores, 1-Aminocyclopropane-1-Carboxylate Deaminase, and the Phytohormone Auxin.

Burkholderia sp. strain Nafp2/4-1b is a rhizobacterium isolated from the rhizosphere of grassland in South Africa. This draft genome report confirms the presence of genes related to iron acquisition, alleviation of abiotic stress in plants, and other essential traits of plant growth-promoting rhizobacteria (PGPR) that signify the potential of this strain as a plant growth-promoting agent.