PGPR with enzymatic activity to improve the growth, yield and oil content of Sesame (Sesamum indicum L.)

Abstract

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 place 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 such approach is the application of plant growth-promoting rhizobacteria (PGPR) linked with nutrient solubilization and plant growth promotion. Phosphorus solubilization by microbes may help to improve 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 HPO4 -2 and increases P-uptake. Some bacteria can solubilize insoluble forms 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, a study was planned to isolate bacteria with phosphorus solubilization and mineralization capability coupled with ACC-deaminase activity with the hypothesis that inoculation of PGPR possessing multi growth promoting-traits would help in improving the growth, yield, and oil content of sesame A series of studies were conducted to evaluate the response of rhizobacterial inoculation. During the preliminary screening approach under axenic conditions, inoculation caused up to 51 increase in seedling length, 36% increase in seedling fresh weight, and 25 % increase in seedling dry weight compared to uninoculated control. In pot trial, inoculation with bacterial isolates caused up to 22, 19, 48, and 43 % increase in shoot length, root length, grain yield, and biomass of sesame over control treatment, respectively. Similarly, in the field, inoculation of plant growth promoting rhizobacteria resulted in a significant increase in plant height, grain yield, biological yield, and straw yield of sesame (up to 26, 37, 25, and 24 % respectively), as compared to uninoculated control. Regarding biochemical parameters, bacterial inoculation also resulted in enhanced oil content, oil yield, protein content, and protein yield over control. The study also demonstrated that multitrait bacteria could be more effective PGPR than a single trait to improve crop growth and yield.