Biosurfactant based formulation of Pseudomonas guariconensis LE3 with multifarious plant growth promoting traits controls charcoal rot disease in Helianthus annus.

Biosurfactants are environment compatible surface-active biomolecules with multifunctional properties which can be utilized in various industries. In this study a biosurfactant producing novel plant growth promoting isolate Pseudomonas guariconensis LE3 from the rhizosphere of Lycopersicon esculentum is presented as biostimulant and biocontrol agent. Biosurfactant extracted from culture was characterized to be mixture of various mono- and di-rhamnolipids with antagonistic activity against Macrophomina phaseolina, causal agent of charcoal rot in diverse crops. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) analysis confirmed the rhamnolipid nature of biosurfactant. PCR analysis established the presence of genes involved in synthesis of antibiotics diacetylphloroglucinol, phenazine 1-carboxylic acid and pyocyanin, and lytic enzymes chitinase and endoglucanase suggesting biocontrol potential of the isolate. Plant growth promoting activities shown by LE3 were phosphate solubilization and production of siderophores, indole acetic acid (IAA), ammonia and 1-aminocyclopropane-1-carboxylate deaminase (ACCD). To assemble all the characteristics of LE3 various bioformuations were developed. Amendment of biosurfactant in bioformulation of LE3 cells improved the shelf life. Biosurfactant amended formulation of LE3 cells was most effective in biocontrol of charcoal rot disease of sunflower and growth promotion in field conditions. The root adhered soil mass of plantlets inoculated with LE3 plus biosurfactant was significantly higher over control. Biosurfactant amended formulation of LE3 cells caused maximum yield enhancement (80.80%) and biocontrol activity (75.45%), indicating that addition of biosurfactant improves the plant-bacterial interaction and soil properties leading to better control of disease and overall improvement of plant health and yield.