Effect of Pseudomonas luteola on mobilization of phosphorus and growth of young apple trees (Ligol)—Pot experiment

• Pseudomonas luteola BN0834 strain has plant growth promoting activities.
• We applicated this strain in two doses into the rhizosphere of young apple trees.
• After inoculation the content of available P in non-rhizosphere soil was higher.
• The amount of P, K and Ca in leaves of inoculated plants was higher.
• The highest total shoot length was also obtained from P. luteola BN0834 application.

The use of phosphate solubilizing bacteria as inoculants may increase the concentration of plant-available phosphorus in soil. Among soil microorganisms, bacteria from the genus Pseudomonas have received considerable attention as plant growth promoters. A phosphate solubilizing bacterium isolated from non-rhizosphere soil collected in Central Poland, was identified as Pseudomonas luteola BN0834 on the basis of biochemical methods and 16SrDNA sequence analysis. P. luteola strain BN08-34 was tested for: solubilization of inorganic and organic compounds of phosphorus (calcium phosphate, zinc phosphate, hydroxyapatite and calcium phytate); indole acetic acid (IAA), siderophore production and biosurfactant production; and the ability to grow on a medium without nitrogen added. Young apple trees, cultivar Ligol (rootstock M26), were grown in a pot-house for 14 weeks in pots filled with nonsterilized soil, classified as a sandy loam. The P. luteola BN0834 was introduced into the soil in a number equal to the number of native phosphate solubilizing microorganisms (PSM) (P. luteola) in soil or in a number ten times higher than the number of native PSM in soil (P. luteola × 10). Shoot numbers; average and total shoot lengths; contents of P, K, Mg and Ca in plant material; contents of available P, K and total Mg in non-rhizosphere soil, changes in the number of cfu (colony forming units) of microorganisms (PSM, cophiotrophs, oligotrophs and fungi) in non-rhizosphere soil and in the rhizosphere of the apple trees were studied. When the higher number of P. luteola BN0834 was introduced into soil without a mineral fertilizer added near the surface of the roots, positive correlations were found between the number of PSM in the apple tree rhizosphere and the content of available P in non-rhizosphere soil and also between the number of PSM in the apple tree rhizosphere and the amount of P, K and Ca in plant leaves. The highest total shoot length was also obtained from P. luteola × 10 application.