Isolation, Identification and Role of Novel Endosymbiotic Bacterium Rhizobium pusence in Root Nodule of Green Gram cv.OUM-11-15 (Vigna radiata L.) under Salinity Stress

In this study, most efficient salinity stress tolerant Rhizobium strain named Rhizobium pusence strain KHDEB5 was identified from root nodules of OUM-11-15 out of fifteen endophytic isolates from root nodules of four (PDM54, SML668, Pusa Baisakhi and OUM-11-15) green gram cultivars from five different locations of Khordha district of Odisha, India and after a series of evaluation. Its 16S rRNA sequence was provided with accession number KY679150 by NCBI. Nodulation behavior of R. pusense strain KHDEB5 was evaluated under different levels of salinity stress (NaCl concentrations) by bioinoculation with green gram (cv. OUM-11-15) seeds. In seed germination bioassay (green gram cv. OUM-11-15) with five nodulating rhizobium strain, R. pusense strain KHDEB5 recorded (31%) higher seedling dry weight with salinity stress upto 500 mM of NaCl when compared with the other strains. The strain R. pusense strain KHDEB5 was found to be most tolerant to salinity (up to 1000 mM NaCl) and also could tolerate up to pH 8.5. In pot culture study, with same seed, Rhizobium pusense strain could enhance N concentration in green gram with salinity stress upto 1000 mM of NaCl. Bioinoculation of most efficient endophyte R. pusense strain KHDEB5 could enhance 112% to 137% N concentration in green gram without salinity stress and 31% with salinity stress upto 1000 mM of NaCl in pot culture studies. R. pusence strain KHDEB5 could be considered most resistant native rhizobium to enhance root nodulation even at salinity stress.