CHARACTERIZATION AND EVALUATION OF OSMOTOLERANT RHIZOBACTERIA FOR ALLEVIATION OF WATER DEFICIT STRESS IN MUSTARD
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Date
2015
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Division of Microbiology ICAR-Indian Agricultural Research Institute New Delhi
Abstract
Drought is the most common stress affecting plant growth and development and it is a
major abiotic stress hindering agricultural productivity in majority of arid and semiarid
regions of the world. Mustardis one of the most important oilseed crops grown in
India. It is generally grown as rainfed crop, however, water deficit stress considerably
impacts its growth and yield. Osmotolerant plant growth promoting bacteria can be
harnessed for their beneficial properties under such conditionsso as to prevent
deleterious effects of water stress on crop.
In the present investigation, a total of 114 morphologically different bacteria
were isolated from the rhizosphere of drought tolerant mustard cultivar DRMR 2352
using various media. Out of these 114 rhizobacterial isolates screened for
osmotolerance, 14 isolates showed higher growth in presence of osmotic stress and
were able to grow in nutrient broth supplemented with 40% PEG 6000. These 14
osmotolerant bacterial isolates were evaluated for their alleviation of water stress in
drought susceptible mustard cultivar Pusa Karishma LES-39. Under in vitro
conditions there was an increase in percent germination and seedling vigour of
inoculated mustard seedling as compared to uninoculated control treatment exposed to
water stress. A pot experiment conducted under water stress conditions revealed
positive effect of inoculation with osmotolerant bacteria on shoot and root fresh
weightand dry weight of mustard. Nearly all the plants inoculated with osmotolerant
bacterial isolates were observed to have significantly higher water content in shoots
and improved water use efficiency under water stress conditions.
Two promising osmotolerant cultures NA D7 and MR D17 were selected for
further studies. Effect of different concentrations of PEG 6000 on their PGPR
activities were determined, like P solubilization, IAA production, GAproduction,
ACC deaminase activity, exopolysaccharide production etc. The selected isolates
improved seed germination and seedling vigour of mustard on exposure to different
levels of water stress. The isolates were identified as Bacillus cereus and Bacillus sp.
by 16S rDNA sequencing.
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A pot culture experiment was carried out under drought and normal soil conditions to
evaluate the effect of these cultures on mustard growth. Inoculation has a beneficial
effect on plant biomass, productivity, oil content and root system architecture under
both normal and water stress conditions.Various plant physiological parameters viz.
amino acid, proline, starch, sugars, phenolics and chlorophyll, content were
significantly enhanced in inoculated plants under water stress conditions. Inoculation
with the osmotolerant bacteria significantly improved membrane stability index and
relative water content; and decreased lipid peroxidation in plants under water stress
conditions. Activity of antioxidative enzymes such as catalase, ascorbate peroxidase,
glutathione reductase and superoxide dismutase were significantly enhanced in
inoculated plants exposed to water stress conditions. Plant phosphorus and potassium
contentswere considerably enhanced under water stress conditions due to inoculation
with selected strains. However, response of the drought susceptible genotype to
inoculation was markedly more than that observed for the tolerant genotype.
Expression of drought responsive genes DREB 2 and DREB 1-2 was considerably
enhanced due to inoculation under water stress conditions.
Thus, osmotolerant bacteria possessing plant growth promoting activities can
be used for drought stress alleviation in crops and to improve plant growth under
water deficit stress.
Description
T-9430
Keywords
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