STUDIES ON ROOT COLONIZATION OF APPLE PLANT BY POTENTIAL Pseudomonas SPECIES IN REPLANT SITES
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Date
2013
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Abstract
ABSTRACT
In the present study, isolation and characterization of indigenous fluorescent
Pseudomonas strains from normal and replant site of apple orchard (Shimla H.P.) was done.
Root colonizing bacteria that exert beneficial effects on plant development via direct or
indirect mechanisms have been defined as plant growth promoting rhizobacteria (PGPR) The
aim of the study to select and to develop PGP strains of fluorescent Pseudomonas species
having efficient root colonizing capacity with direct and indirect plant growth promoting
activities for management of replant problem of apple. The fourteen Pseudomonas species
isolates were screened out for various plant growth promoting activities like siderophores,
phosphate solubilization, antifungal activity, plant growth regulators (auxins, cytokinins and
gibberellins), lytic enzymes and production of HCN and ammonia. On the basis of PGPR
activities, nine isolates were genotypically characterized by RAPD and 16S rRNA gene
sequencing. Out of them, two best isolates (Pn-13-San and An-16-Kul) were selected for 16S
rRNA gene sequencing. Pn-13-San showed 99% homology with Pseudomonas aeruginosa
M18 with accession number (NC_017548). An-16-Kul showed 99% homology with
Pseudomonas aeruginosa PAO1 with accession number (NC_002516.2). These two strains
exploited for the management of replant problem of apple in replant site at Maggota (Shimla).
In replant field these two strains used individually and their consortia for treatment of apple
rootstocks before planting. The performance of apple plants was much better in terms of root
colonization capacity, plant establishment and increase in plant growth in terms of plant
height, number of nodes and branches, chlorophyll content of leaves and NPK of rhizosphere
soil over their respective control after nine and twenty months of plantation. These strains can
be further exploited for management of replant problem of apple after conducting few more
field trials in replant sites and can have great importance in the field of horticulture.