Development of promiscuous and effective rhizobia nodulating kharif legumes
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Date
2018
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CCSHAU
Abstract
Clusterbean, cowpea, mothbean, mungbean, pigeonpea and urdbean are the commonly grown
kharif legumes of arid and hyper-arid zones. Inoculation of effective and promiscuous rhizobia
improves the nitrogen fixation as well as plant biomass yield of legumes. So, the present investigation
has been undertaken for development of promiscuous and effective rhizobia nodulating kharif legumes.
A total 209 rhizobial isolates were isolated from 31 soil samples collected from different districts of
South-West Haryana and Rajasthan. All rhizobial isolates were checked for their nodulation ability and
efficiency in six different kharif legumes. Three rhizobial isolates (PKR177, PKR188 and PKR194)
have ability to nodulate all these six crops but with poor nodulation efficiency. So, these three rhizobial
isolates were mutagenised by EMS (0.15%) for enhancing nodulation efficiency in all six legumes and
it was found that, out of 300, only 4 rhizobial mutants (PKR177m30, PKR188m85, PKR194m24 and
PKR194m93) exhibited increase in nodulation efficiency in all the legumes. Rhizobial mutant
PKR188m85 was tagged with gfp gene to check its nodulation occupancy in all the legumes. Twenty
five native rhizobial isolates, 4 mutants and one GFP marked strain having capability of nodulating
more than three crops were evaluated for different traits. Most of the native and mutant rhizobia were
able to grow up to 40oC, 4% salt and 30% PEG concentration. All rhizobia were able to produce IAA
and ammonia, however, 47 and 63% rhizobia had the ability of bacteriocin production and phosphate
solubilization, respectively, whereas, 83% of rhizobia were able to utilize ACC. Most of rhizobia were
found to have intrinsic resistance to ampicillin, chloramphenicol, nalidixic acid and streptomycin upto
concentration of 100 μg/ml. All the rhizobia showed the presence of nodC gene, however, nifH gene
amplification was observed in 26 rhizobia. ARDRA results showed that all the isolates were
distributed in to two major groups with sub and sub groups and divergence among these started at 63
percent similarity with restriction enzymes, MspΙ and HaeΙΙΙ. Rhizobial mutants PKR177m30 and
PKR188m85 showed better nodulation efficiency and plant growth parameters than control in chillum
jar and pots under both sterilized as well as unsterilized conditions. It was observed that promiscuous
GFP marked strain showed more than 80% nodule occupancy under unsterilized conditions.The
promising promiscuous rhizobial mutants were identified as Rhizobium sp. on the basis of ribo-typing
of partial 16S rRNA gene.
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