Effect of Phosphate Solubilizing Bacteria on Growth of Apple in Replant Sites
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Date
2014
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YSPU
Abstract
The ability of fluorescent Pseudomonas isolates to convert insoluble forms of phosphorus to an
accessible form is an important trait of phosphate solubilizing bacteria to overcome replant problem of
apple to some extent. Phosphorus is an essential nutrient for plants, but it is often not available due to its
fixation in soil. Little is known about the composition of phosphate solubilizing bacteria specially,
fluorescent Pseudomonas diversity associated with apple rhizosphere. Therefore, the objective of the
present study was to isolate fluorescent Pseudomonas isolates from normal and replant sites of apple
orchard. The fluorescent Pseudomonas sp. are plant beneficial rhizobacteria with all the direct and indirect
plant growth promoting activities like siderophores, phosphate solubilization, antifungal and production of
HCN; ammonia; plant growth regulators (auxins, cytokinins and gibberellins) and lytic enzymes. Six
strains producing high levels of P- solubilization and other PGP activities were selected for further
characterization and identified by 16S rRNA gene sequencing and RAPD analysis. Accession no. provided
from NCBI to P. putida KF751235, P. fluorescens KF751236 and to four strains of P. aeruginosa were
KJ522923, KJ522924, KJ500025 and KJ500026. Different organic acids were estimated through HPLC by
selecting four strains of Pseudomonas aeruginosa i.e. An-E, An-F, An-G and An-H which were also used
for bioformulation development. Succinic acid, malonic acid, citric acid and malic acid were detected as
major organic acids with small percentage of tartaric acid, fumaric, quinic, schimic and lactic acid. The
production, partial purification and characterization of acid and alkaline phosphatase was done from best
selected strain of Pseudomonas sp. An-H with molecular weight 20.1 kDa and 66 kDa, respectively. This
phosphorus solubilization property of fluorescent Pseudomonas help in the growth and establishment of
apple rootstocks in replant sites and results in increase of Pseudomonas population and decreased total
rhizobacterial and fungal spopulation. Therefore these strains can be exploited for the management of
replant problem of apple.
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Keywords
bacteria, planting, inorganic acid salts, enzymes, biological development, acidity, productivity, apples, alkalinity, fungi