Isolation and characterization of native Rhizobium from root nodules of raikia french bean growing area of Odisha-Supplementary Data

Injudicious application of nitrogenous fertilizers leads to soil quality deterioration which results into yield loss. The application of biofertilizer containing native efficient rhizobia enhances the nodular properties, N-fixation and soil quality. Therefore, fifty strains of Rhizobium were isolated from root nodule of Raikia french bean and among them only two isolates viz., RBHR-15 and RBHR-21 were confirmed as Rhizobium. The isolates were unable to grow under anaerobic conditions and failed to produce ketolactase enzyme, showed a negative response for gelatin liquefaction and Simmon’s citrate agar test, responded positively towards the indole test, MR-VP, TSI test and could produce NH4+ from peptone in the growth medium. The isolate RBHR-15, could reduce H2S and nitrate whereas, RBHR-21 could not. The growth of both isolates was luxuriant in the nutrient broth containing 1% NaCl and decreased with an increase in the concentration of NaCl and grew profusely in the pH range of 6-8. The generation time of RBHR-15 and RBHR-21 were 16.4and 10.6 h, respectively. The 16s rRNA of both isolates was sequenced and submitted to the National Center for Biotechnology Information (NCBI). The isolates RBHR-15, and RBHR-21 were assigned accession numbers MN480514 and MN480516.

Isolation and characterization of native Rhizobium from root nodules of raikia french bean growing area of Odisha

Injudicious application of nitrogenous fertilizers leads to soil quality deterioration which results into yield loss. The application of biofertilizer containing native efficient rhizobia enhances the nodular properties, N-fixation and soil quality. Therefore, fifty strains of Rhizobium were isolated from root nodule of Raikia french bean and among them only two isolates viz., RBHR-15 and RBHR-21 were confirmed as Rhizobium. The isolates were unable to grow under anaerobic conditions and failed to produce ketolactase enzyme, showed a negative response for gelatin liquefaction and Simmon’s citrate agar test, responded positively towards the indole test, MR-VP, TSI test and could produce NH4+ from peptone in the growth medium. The isolate RBHR-15, could reduce H2S and nitrate whereas, RBHR-21 could not. The growth of both isolates was luxuriant in the nutrient broth containing 1% NaCl and decreased with an increase in the concentration of NaCl and grew profusely in the pH range of 6-8. The generation time of RBHR-15 and RBHR-21 were 16.4and 10.6 h, respectively. The 16s rRNA of both isolates was sequenced and submitted to the National Center for Biotechnology Information (NCBI). The isolates RBHR-15, and RBHR-21 were assigned accession numbers MN480514 and MN480516.

Acid and salt tolerance behavior of Rhizobium isolates and their effect on microbial diversity in the rhizosphere of redgram (Cajanus cajan L.)

Experiments were conducted in two phases, first under in vitro condition to study the stress tolerant ability and then in pot experiment to study the effect of Rhizobium isolates on rhizospheric microbial activity. The strain CHRS-7 could tolerate the pH 4.0, whereas RAN-1 and RAB-1 could not. The growth of all the strains was luxuriant in 1% NaCl solution and decreased with increase in the concentration of NaCl. All the strains could produce the phytohormone indole acetic acid (IAA) by metabolizing different carbon sources. The highest amount of IAA was produced by RAB-1 (81 µg/mL), CHRS-7 (78 µg/mL) and RAN-1 (72 µg/mL) by metabolizing mannitol, glucose , and sucrose, respectively. The higher bacteria and rhizobial population was enumerated in the treatment with inoculation of Rhizobium strains and added with 50% of soil test dose of nitrogen whereas higher fungi population was enumerated with the treatment receiving 150% of a soil test dose of nitrogen. The soil enzymes activity, microbial biomass carbon and nitrogen were also higher with a lower dose of external sources of N (50% of a soil test dose) and decreased with increase in nitrogen dose.

Effect of different carbon, nitrogen and vitamine sources on exopolysaccharide production of Rhizobium species isolated from root nodule of redgram

Three bacterial strains CHRS-7, RAB-1 and RAN-1 were isolated from root nodules of redgram (Cajanus cajan) and identified as Rhizobium sp. based on 16S rDNA sequence homology and assigned accession number MH636329, MH636773 and MH541051, respectively by National Center for Biotechnology Information (NCBI). All the strains could produce copious amount of exopolysaccharides in yeast extract manitol broth medium. All the three strains had different stationary phases but the bacterial growth and exopolysaccharides production occurred simultaneously. The glucose (1.5 %), manitol (2.0%) and sucrose (1.5%) were the preferable carbon sources of CHRS-7, RAB-1 and RAN-1 respectively, for both growth and EPS production. Among the nitrogen sources glycine (0.1%), NaNO3 (0.1%) and KNO3 (0.1%) were the preferable N sources for CHRS-7, RAB-1 and RAN-1 respectively, whereas, CHRS-7, RAB-1 and RAN-1 preferred biotin 1.5%, 2.0% and 1%, respectively.