Isolation and characterization of Rhizobium spp. for its plant growth promoting potential in Lucerne (Medicago sativa L.)
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation was undertaken to access the effect of rhizobial isolates on plant
growth and symbiotic parameters in Lucerne (Medicago sativa L.).Forty rhizobial isolates
were identified and characterized culturally, morphologically, biochemically and found
belonging to genera Rhizobium. The isolates were functionally characterized on the basis of
phosphate solubilization, Indole acetic acid, siderophore, cyanide and gibberellic acid
production. Indole acetic acid production ranged from 2.6 -77.7 μg/ml in presence of
tryptophan after 3 days of incubation and increased to 2.9-101.7 μg/ml on 5th day.The range
of PSI (Phosphate solubilization index) was 13-17 mm with highest solubilizing index shown
by LNR-6, LNR-20, LNR-23 and LNR-39 (17mm).Twenty eight of the forty isolates were
able to produce siderophore as evidenced on Chrom-azurol-S-agar, maximum catecholate
type siderophore produced by LNR-39 (43.4 μg/ml). 57.5% isolates produced HCN out of
which 13 % were strong and 39.1% were moderate producers. The gibberellic acid production
ranged from 41.2 -96.6 μg/ml with LNR-39 (96.6 μg/ml) being the potent gibberellic acid
producer. The study carried out showed that isolates LNR-2,LNR-4, LNR-6, LNR-22, LNR-
32 and LNR-39 exhibited growth and functionality traits which were at par, hence they were
selected for field trail. The field experiment revealed enhanced stem and root length,dry
weight of nodules, nitrogen content, leghemoglobin and chlorophyll content , green fodder
yield under Rhizobium treatment. Thus, the present study revealed that treatment with
Rhizobium LNR-39 and treatment LNR-4 were effective for plant growth promotion and
enhanced symbiotic effeicency in Lucerne.
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