ISOLATION AND SCREENING OF DROUGHT AND SALINE TOLERANT RHIZOSPHERIC PLANT GROWTH PROMOTING BACTERIA FROM SALINE SOILS AND THEIR EFFECT ON GROWTH AND YIELD OF GROUND NUT (Arachis hypogaea L.)
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Date
2018
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Acharya N.G. Ranga Agricultural University
Abstract
Stress tolerant plant growth promoting rhizobacteria (PGPR) can enhance plant growth under stress conditions by production of exopolysaccharides and ACC deaminase enzyme activity. In the present study 48 stress tolerant PGPR were isolated from rhizospheric soil of saline effected areas and were tested for different plant growth promoting activities. Out of 48 isolates, 15 were Rhizobium, 15 Pseudomonas, 10 sulphur oxidizing bacteria (SOB) and 8 potassium releasing bacteria (KRB). Out of these 48, one efficient isolate was selected from each group i.e., Rhizobium (BRR3), Pseudomonas (VKP2), potassium releasing bacteria (AKK2) and sulphur oxidizing bacteria (NJS2) for further studies. These four isolates contain high ACC deaminase activity [BRR3 (+++), VKP2 (+++), AKK2 (+++), NJS2 (++)] and high exopolysaccharide production BRR3 36.2 mg ml-1, VKP2 30.2 mg ml-1, AKK2 21.6 mg ml-1, NJS2 24.6 mg ml-1. All the isolates were positive for the production of siderophore, IAA, ammonia and phosphate solubilization.
These selected strains were tested in soil to assess their effectiveness against stress tolerance to improve the growth of groundnut under moisture stress conditions in saline soils. Pot culture experiment was conducted with groundnut crop at different water holding capacities (25 %, 50 % and 75 % WHC).
The results revealed that reduction in soil moisture levels significantly reduced the growth of groundnut. However, inoculation of groundnut with stress tolerant rhizobacteria isolated from saline effected areas containing ACC deaminase and exopolysaccharide production ability significantly increased stress tolerance and enhanced the growth and yields of groundnut.
These stress tolerant PGPR improved the growth parameters like plant height (35.50 cm), number of nodules per plant (69), number of pods per plant (11.0), number of seeds per pod (1.8) and also seed yield (1415.7 kg ha-1) compared to control without inoculation.
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Application of stress tolerant bacteria significantly enhanced the activity of soil enzymes like dehydrogenase (226.50 μg of TPF g-1 of soil d-1), phosphatase (alkaline 140.23 μg pNP g-1 h-1, acidic 125.0 μg pNP g-1 h-1) and urease (119.03 μg urea g-1 h-1), highest enzyme activity observed at flowering stage of groundnut when all the PGPRs applied in combinations.
Other Physico-chemical properties of soil like pH (7.90), EC (3.27 dSm-1), organic carbon (0.77 %), nitrogen (398.18 kg ha-1), phosphorous (96.99 kg ha-1), potassium (436.73 kg ha-1) and N, P, K content of plant (1.71, 0.63 and 1.81 % respectively) also improved at flowering stage of groundnut. In addition to this proline content of plant was increased under stress conditions i.e., at 25 % WHC, it was recorded as 66.97 μ moles g-1. Finally, from these results it is concluded that combined application of stress tolerant PGPRs significantly increased the growth and yield of groundnut by 38.63 %. 33.89 % and 26.26 % at 75 %, 50 % and 25 % moisture levels respectively compared to control.
Description
D5597
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