Evaluation of potassium solubilizing bacteria for use as biofertilizer in wheat (Triticum aestivum L.)
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Date
2015
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Publisher
CCSHAU
Abstract
In the present study, one hundred and fifty rhizobacterial isolates were obtained from rhizosphere soil
of wheat and mustard after plating serial dilutions on modified Aleksandrov medium containing
mica powder as potassium source. These rhizobacterial isolates along with 11 reference strains
were screened for their potassium solubilizing ability and 61 isolates were found to possess
potassium solubilizing activity. These potassium solubilizing isolates were further analyzed for
different plant growth-promoting activities like phosphorus solubilization, IAA production, ACC
utilization and siderophore production. The IAA production was observed in 93.44% of the isolates and
it varied from 1.21 to 12.48 µg/ml. Twenty nine isolates showed efficient phosphorus solubilization
and ACC utilization was observed in 57 rhizobacterial isolates. Eight isolates showed siderophore
production. On the basis of these beneficial activities, two isolates HMP27 and HMP45 were selected
for strain improvement by using nitrosoguanidine mutagen and mutants having increased and low
potassium solubilization activity were isolated. Production of organic acids i.e., oxalic, tartaric, citric,
malic and succinic acid was determined in the selected 20 isolates/strains/mutants using HPLC. Four
acids were detected in different isolates and mutants in varying amounts and malic acid production was
not detected in any of the culture. Inoculation of potassium solubilizing strain HMP45 along with
addition of rock K showed 110% and 117.54% increase, whereas HMP27 showed 100% and 103.50%
increase in RDW and SDW, respectively in comparison to uninoculated plants containing rock K alone
at 60 days of sowing. Inoculation of K over- solubilizing mutant HMP45-M39 along with rock K
showed 70% and 89.47% increase, whereas mutant HMP27-M23 showed 115% and 124.56% increase
in RDW and SDW, respectively as compared to rock K added but uninoculated plants. At 90 days
after sowing, inoculation of potassium solubilizing parent strain HMP45 along with rock K showed
47.05% and 102.63% increase, whereas inoculation with isolate HMP27 showed 41.17% and 107.89%
increase in RDW and SDW, respectively as compared to uninoculated plants. Inoculation of K oversolubilizing mutant HMP45-M39 along with rock K showed 52.94% and 81.57% increase and HMP27-M23 mutant inoculation caused 64.70% and 92.10% increase in RDW and SDW, respectively in
comparison to rock K containing uninoculated plants. These K-solubilizing bacteria HMP27 and
HMP45 could be further tested for plant growth improvement under field conditions.
Description
Keywords
Rhizosphere bacteria, Potassium solubilization, Phosphorus solubilization, IAA production, ACC utilization, Siderophore production, Nitrosoguanidine mutagenesis organic acids, Wheat growth