SCREENING OF PHYLLOSPHERIC BACTERIA AGAINST ABIOTIC STRESS IN COTTON (Gossypium spp.)
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Date
2019
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PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
Drought is one of the major abiotic stress limiting the productivity of agriculture in
India, which effects germination, growth and productivity of crops. Successful
remediation of drought prone areas for crop production is based on sustainable
management practices which involves the use of drought tolerant microorganisms which
are of low cost and easily adaptable method by the farmers. Present investigation was
focussed towards isolation of phyllospheric bacteria from cotton and in vitro screening of
the isolates for drought tolerance and plant growth promoting (PGP) attributes and
evaluation of the efficient bacterial isolates on cotton crop under drought stress conditions
by pot culture studies.
As many as 31 phyllospheric bacterial strains were isolated from four villages of
Rangareddy and Warangal Districts of Telangana, as the districts are cotton growing
areas. The isolates were culturally, morphologically and biochemically characterized. The
isolates were screened in vitro for plant growth promoting attributes like phosphorous,
potassium and zinc solubilization, siderophore, hydrogen cyanide production (HCN) and
indole acetic acid (IAA) production and further screened for drought tolerance, 1 - amino
cyclopropane - 1 - carboxylate (ACC) deaminase activity, exopolysaccharide (EPS)
production and proline content. Results revealed that among the 31 isolates, all the
isolates showed tolerance at - 0.25 (Mega pascal) Mpa and - 0.50 Mpa, 28 isolates showed
tolerance at - 0.73 Mpa and 15 isolates showed tolerance at -1.25 Mpa. seven isolates
utilized ACC as a sole nitrogen source, nine strains produced EPS, phosphorous was
solubilized by 15 isolates, potassium was solubilized by 13, zinc was solubilized by 13
isolates, IAA was produced by nine isolates, HCN was produced by 21 isolates and
siderophores was produced by 13 isolates.
Five efficient bacterial isolates were selected and identified by 16S rRNA gene
sequencing. BLAST search results through NCBI revealed isolate CPB 23 with
Pseudomonas stutzeri, isolate CPB 24 with Acinetobacter spp., isolate CPB 25 with
Bacillus mojavensis, isolate CPB 27 with Pseudomonas chlororaphis and isolate CPB 31
with Enterobacter asburiae.
A pot culture experiment was conducted during Rabi, 2018. Drought stress was
induced by 10 %, 20 % and 30 % PEG-6000 to create - 0.25 Mpa, - 0.50 Mpa and - 0.75
Mpa respectively. The results revealed that plant height at 90 DAS was found
significantly highest in T4 (Strain CPB 24 + 30 % PEG-6000) with 46.00 cm, Seedling
vigour index at 90 DAS was found significantly highest in T4 with 58.52, fresh weight at
90 DAS was registered significantly highest in T4 with 11.36 g and dry weight was found
significantly highest in the T4 with 5.08 g. Total bacterial population was enumerated
both in soil and leaf samples and found to be significantly highest in T4 (Strain CPB 24 +
30 % PEG-6000) with 4.65, 5.70 and 5.20 × 107 CFU gm-1
of soil at 30, 60 and 90 DAS
respectively and in leaf sample, it was also found to be significantly highest in T4 (Strain
CPB 24 + 30 % PEG-6000) with 4.75, 6.25 and 5.60 × 105 CFU gm-1
of leaf at 30, 60
and 90 DAS respectively. Influence of drought tolerant strains on proline content in the
leaf at flowering stage was assessed and found highest in the T4 (660 µg / g FW). Number
of bolls per plant was measured at harvest and found highest in T4 (Strain CPB 24 + 30
% PEG-6000) with 12.66, boll weight was found significantly highest in T4 (5.36 g), seed
cotton yield of plants was also found to be highest in T4 with 1027.77 kg ha-1
.
Among all the treatments, T4 (Strain CPB 24 + 30 % PEG-6000), T7 (Strain CPB 31
+ 30 % PEG-6000) and T8 (Consortium + 20 % PEG-6000) treatments played a major
role in increasing the production and productivity of cotton in pot culture by mitigating
drought stress and among the individual inoculations CPB 24 and CPB 31 strains
inoculated treatments showed good growth as well as yield parameters when compared
with control. This might be due to presence of minerals solubilization, siderophore
production, phytohormones production. Another mechanism can be reduction of stress
induced ethylene by ACC deaminase enzyme produced by the bacteria, thereby
improving the plant growth in drought stress conditions. Hence, the research revealed that
these strains can be used to mitigate drought stress in the cotton growing drought prone
areas of Telangana.
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D10,398