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.