Characterization of plant growth promoting rhizobacteria isolated from the rhizosphere of carob tree ( Ceratonia siliqua L.) in Morocco

Plant growth promoting rhizobacteria (PGPR) are beneficial bacterial that colonize plant roots and enhance plant growth by a wide variety of mechanisms. Seven isolates of bacteria were successfully isolated and phenotypically, biochemically, physiological and molecular characterized. Subsequently to investigate the effect of PGPR isolates on the growth of carob tree, a pot culture experiement was conducted as Centre for Innovation and Technology Transfer (CITT), Meknes, Morocco. All the isolates were gram negative, rods, motile, able to grow on YDC medium and citrate simmons positive, degrade glucose, fructose and mannitol, capable of hydrolyzing esculin and starch. All strains are able to produce (74-150µgml-1) of indole acetic acid, nitrogen fixatin and all isolate are unable to produce ammonia, chitinase and cellulase, the strains 2018-3, 2018-4 and 2018-5 showed protease activity. The pecentage of solibilization of phosphate varied between 15% to 45%, the maximum phosphate solubilization was identified by stain 2018-4. Sequencing of 16SrRNA genes led to the identification of two family of bacteria : Bacillaceae and Pseudomonadaceae. The species of bacteria are : Bacillus thuringiensis, two of Bacillus flexus, two of Pseudomonas gessardii, Bacillus cereus and Bacillus thaonhiensis. The analysis the result showed that the highest vegetative growth was obtained from stain 2018-4 such as plant height (13.6cm), root length (13.65cm), fresh weight of the aerial part (1.09g) and fresh weight of the root part (0.42g) in comparison to untreated plant.