Phosphorus-Solubilizing Rhizobacterium Enhances Growth, Yield and Oil Content of Sesame in a Calcareous Soil

Sesame has nutritive, medical and biochemical importance which increases its demand worldwide. In Pakistani soils, which have calcareous nature, phosphorus (P) retention and mobilization take places due to precipitation and adsorption which makes them unavailable to the plants and causes a reduction in the sesame yield. For increasing sesame crop productivity, the development of cost effective, sustainable and environmentally friendly cultivation technologies are inevitable. One of such approach is the application of plant growth-promoting rhizobacteria (PGPR) linked with nutrient solubilization and plant growth promotion. Phosphorus solubilization by microbes may be helpful in improving P-availability in arable soils apart from other conventional methods of phosphate fertilization. Phosphatase enzymes are released by these bacteria which convert organic soil phosphorus into its inorganic forms such as H2PO4- and HPO42- and increases P-uptake. Some bacteria have capability to solubilize insoluble form of phosphorus by releasing organic acids. Furthermore, some microorganisms can increase P-uptake indirectly by improving root growth through their ACC-deaminase activity. Based on the microbial potential to regulate the phosphorus availability, P-solubilizing bacteria were isolated and screened for their ability to improve plant growth by evaluating them against different plant growth promoting traits. Five promising strains of PGPR [AA-06 (Pseudomonas fluorescens), AA-18 (Pseudomonas spp.), AA-27 (Psychrobacter spp.), AA-39 (Bacillus spp.) and AA-45 (Bacillus aquimaris)] from a series of isolation and characterization campaign were selected to evaluate the effect of inoculation on field-grown sesame. Data showed that bacterial inoculation caused up to 26, 12 and 37% increase in plant height, 1000 seed weight and sesame seed yield in comparison with uninoculated control, respectively. Biological yield, straw yield and harvest index were also enhanced by 25, 24 and 10%, respectively, over uninoculated control. Similarly, there were significant increases in Seed oil (9%) and protein (23%) contents than control in response to rhizobacterial inoculation. From the results, it can be concluded that P-solubilizing multi-trait bacteria can be used to enhance the mineral nutrition, growth and yield of sesame. (C) 2020 Friends Science Publishers