Abstract
Phosphorus (P) is one of the major essential macronutrient for plant growth. Phosphate solubilizing bacteria (PCB) is a group of heterotrophic bacteria capable of solubilizing organic and inorganic phosphorus from insoluble compounds, releasing phosphate available for plant uptake. In this study endophytic bacteria were isolated form nodules of French bean grown in different intercropping systems. Only 14 out of 158 endophytic isolates were able to solubilize tricalcium phosphate (TCP). None of them were observed to solubilize FePO4 and AlPO4. Eight isolates formed solubilization zones larger than 3 mm and were used for further test. The TCP solubilization was measured in liquid Pikovskaya medium and ranged from 14-182 μgml-1 of soluble phosphorus. TCP solubilization was correlated with acidity and pH decreasing from 7.4 to 5.57 and 4.91 for the lowest and the highest solubilizer, respectively, were observed. The most efficient isolate MP18 was selected and identified as Pseudomonas sp. according to 16S rRNA gene analysis.
Highlights
Phosphorus (P) is an essential mineral nutrient most commonly limiting the growth of crops
All bacterial isolates were screened on Pikovskaya (PVK) (gl-1: yeast extract, 0.5; agar, 15; glucose, 10; Fe SO4, 0.0001; MnSO4, 0.0001; MgSO4 x 7H2O, 0.1; KCl, 0.2; (NH4)2SO4, 0.5) growth medium supplemented with 5gl-1 tricalcium phosphate (TCP) for P-solubilization potential
Bacterial colonies surrounded by a halo on PVK medium were assumed to be capable for P-solubilization and selected for further assay on PVK and National Botanical Research Institutes Phosphate (NBRIP) (gl-1: glucose, 10; (NH4)2SO4, 0.1; KCl, 0.2; MgSO4 x 7H2O, 0.25; MgCl2 х 6Н2О, 5; agar, 15) mediums (Kapri & Tewari 2010)
Summary
Phosphorus (P) is an essential mineral nutrient most commonly limiting the growth of crops. The phosphate fertilization of soils has always been important because vast areas of agricultural land can be poor if the soil has a phosphate deficiency. Phosphorus is typically insoluble or poorly soluble in soils (Banerjee et al 2010). Soil P dynamics is characterized by physicochemical (sorptiondesorption) and biological (immobilizationmineralization) processes (Khan et al 2009). Anthropogenic addition to the soil can be precipitated into insoluble forms such as TCPtricalcium phosphate [Ca3(PO4)2], FePO4 and. Jošić* Institute of Soil Science, Teodora Drajzera 7, 11000 Belgrade, Serbia
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