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DIVERSITY AND FUNCTIONS OF PHOSPHATE SOLUBILIZING RHIZOBACTERIA ASSOCIATED WITH APPLE SEEDLINGS

KrishiKosh

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Title DIVERSITY AND FUNCTIONS OF PHOSPHATE SOLUBILIZING RHIZOBACTERIA ASSOCIATED WITH APPLE SEEDLINGS
 
Creator MEHTA, PREETI
 
Contributor SHIRKOT, C.K.
 
Subject bacteria, inorganic acid salts, planting, vegetative propagation, biological development, productivity, sampling, acidity, growth promoters, apples
apple, bacteria for increasing plant yields.
 
Description ABSTRACT
The ability of a few soil microorganisms to convert insoluble forms of phosphorus to an accessible
form is an important trait in plant growth-promoting bacteria for increasing plant yields. Little is known about
the composition of phosphate solubilizing bacterial (PSB) diversity associated with rhizosphere of apple trees.
Therefore, the objective of the present study was to investigate the diversity of PSB population associated with
rhizosphere of soil and roots of apple and characterize them for multifarious plant growth promoting traits and
to test the hypothesis, whether root exudates of apple trees exert a selective pressure on the proliferation of
similar or different phosphate solubilizing plant growth promoting rhizobacterial population. Two hundred and
six phosphate solubilizing bacteria were isolated by using culture dependent procedure from rhizosphere soil
and endorhizosphere of apple trees of four locations viz., Chamba, Shimla, Kinnaur and Kullu of Himachal
Pradesh. All the PSB isolates were screened for plant growth promoting traits (PGPT), including IAA
production, siderophore, HCN, chitinase synthesis ability and antifungal activity against D. necatrix. IAA
production was detected in 50 isolates (24.2%), siderophore synthesis in 53 isolates (25.7%), HCN in 40 isolates
(19.4%), chitinase synthesis ability in 61 isolates (29.6%) and percent growth inhibition against D. necatrix in
61 isolates (29.6%). The diversity index (Shannnon-Weaver index) revealed that PGPT-possessing PSBs in
rhizosphere soil were more diverse than root endosphere. Eighty five of total 206 PSB isolates possessed one or
more than one plant growth promoting traits, hence these 85 PGPT- possessing PSBs were selected further for
RAPD analysis. After RAPD- PCR analysis with primer RBa-4, 85 PSBs were divided in to five major groups.
Sixteen representative PSB isolates from RAPD groups (3, 2, 8, 1, 2 isolates of Ist, 2nd, 3rd, 4th and 5th group,
respectively.) were identified further by 16S rRNA analysis. The 16S rRNA analysis identified 16 PSBs as
Bacillus subtilis, B. licheniformis, B. pumilus, B. altitudinis, B. methylotrophicus and B. firmus. Among 206
PSBs, a highly efficient P-solubilizing isolate was selected and presumptively identified as Bacillus subtilis
CB8A. The isolate solubilized tri-calcium phosphate and produced substantial amount of soluble phosphorus
(823 mg/l) in Pikovskaya’s (PVK) broth and exhibited the production of IAA (16.2 μg/ml), siderophore
(85.21%) and growth inhibition against D. necatrix (56.67%). P- solubilization of B. subtilis CB8A was
inversely correlated with pH (r = – 0.78) and positively correlated siderophore production (r = 0.81), IAA (r =
0.58) and antifungal antibiotic activity against D. necatrix (r = 0.63). Gluconic acid (1.43%) and citric acid
(0.67%) were detected as the major organic acids with small percentages of 2- ketogluconic acid (0.34%),
formic acid (0.15%), oxalic acid (0.10%) and fumaric acid (0.03%) during TCP solubilization by the B. subtilis
CB8A. P- solubilization and nitrogen fixing abilities of the isolate CB8A were confirmed by amplification of gdh
and nifH genes. Thus, the ability of performing multifarious plant growth promoting activities in tandem
suggest B. subtilis CB8A a novel PSB isolate for plant growth promotion and has significance to develop a costeffective
ecofriendly multifunctional biofertilizer for use in apple orchards, the most important cash crop in
Himachal Pradesh.
 
Date 2016-06-23T14:49:05Z
2016-06-23T14:49:05Z
2012
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/67869
 
Language en
 
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