Efficient nitrogen fixing rhizobial isolate infecting Vigna radiata L.

Among 972 rhizobia, isolated from nodules of different verities of Vigna radiata, 67 isolates were found to be potential ones on the basis of plant growth promotion/ increased plant biomass. These isolates were further screened, where, only six potential isolates, showed higher plant biomass, maximum nodule numbers and higher nitrogenase activity, were selected for further studies. Maximum range of fresh weights of nodule per plant was shown again by isolate R0132 and noticed to be 261.37 mg nodule/plant. Nitrogenase activity of plant nodule inoculated with different rhizobial isolates varied from 2.56 to 3.21 :g/mg/nodule. When growth abilities of these isolates studied, it had been observed that with different nitrogen sources, isolate R0132 was found to be the best candidate as it utilized a wide range of nitrogen and carbon sources and was able to grow at slightly higher temperature i.e. 32oC and slightly acidic (pH 6.0) and alkaline (pH 8.0) conditions. Furthermore, this isolate demonstrated the ability to grow in presence 50mM concentration of NaCl.

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