Inoculation with Azospirillum brasilense enhances the quality of mesquite Prosopis juliflora seedlings

Inoculation of mycorrhizal fungi and rhizobacteria in plants can improve their growth and physiological status, which could be particularly important for agricultural and forestry plants used for the revegetation of arid areas. Prosopis juliflora is a forest pioneer species that is drought resistant and has multiple uses (fodder, shade and shelter for livestock; timber and firewood, live fences and windbreaks in agroforestry systems). Azospirillum brasilense is a rhizobacterium that improves the growth of many agricultural crops. The hypothesis of this study was that P. juliflora seedlings produced in the nursery can respond positively to inoculation with A. brasilense CECT 590. Five months after inoculation, we examined the growth, water relations (osmotic potential at full turgor, osmotic potential at zero turgor, and the modulus of elasticity at full turgor), and concentration and content of macronutrients (N, P, K, Ca and Mg) in the seedlings. Subsequently, a trial was conducted to analyse root growth potential. A. brasilense CECT 590 inoculation caused an osmotic adjustment in P. juliflora seedlings but decreased the elasticity of the cell walls. Inoculation with A. brasilense CECT 590 significantly improved plant growth due in part to an increase of N concentration in the seedlings. A. brasilense CECT 590 inoculation also caused an increase in the root growth potential. The increased growth of P. juliflora seedlings inoculated with A. brasilense was probably caused by more than one mechanism. Inoculation with A. brasilense at the nursery may be a suitable technique for producing improved seedling material for restoration purposes.