In vitro Evaluation of Groundnut (Arachis hypogea L.) Rhizospheric Bradyrhizobium Traits for Dinitrogen Fixation

Abstract

Aims: To decipher the nitrogen fixing potential of Bradyrhizobium sp. Study Design: Random sampling method was followed for the representative soil sample collection and Completely Randomized Design was used for the in vitro experiments. Methodology: Six random locations in the Cuddalore district of Tamil Nadu (India) were selected and groundnut rhizospheric soil samples were collected during Feb 2019. Traits of Bradyrhizobium sp. were isolated by serial dilution method. Followed by the purification of isolates and the purified isolates were subjected for biochemical characterization studies. After confirming, the traits were evaluated and graded for their nitrogen fixing ability by Microkjeldahl assay. Results: The highest count of Bradyrhizobium cells, reaching, 5.87 log10 CFU g-1 of dry soil was recorded from the samples of rhizosphere soil, collected at Thiruvamur location (Cuddalore taluk). Whereas the lowest population was recorded in samples collected from Ramapuram location of Cuddalore district. In terms of nitrogen fixation efficiency per gram of mannitol, the strains BM-1 and BM-5 fell into the first classification, while the second category included BM-3 and BM-6, followed by BM-2 and BM-4 to the third category based on their performance. Conclusion: This study, clearly deciphers the Nitrogen fixing potential of Bradyrhizobium traits of groundnut crop and the species holds the promise of using them as the efficient nitrogen fixers in legume crops in future.