Transposon Induced Nitrogenase in Rhizobium japonicum Infecting Vignaradiata

Abstract

The present study established a transposon mutagenesis procedure for Rhizobium japonicum forming symbiotic association with Mung bean (Vigna radiata). Suicide plasmid pko3 introduce the transposon Tn3 in to Rhizobium japonicum via Escherichia coli mediated conjugation and successfully generated 800 mutants with frequency of 3.7 × 10-6. These 800 mutants along with rifampicin resistant mutant and wild strain were screened for nodulation, which showed 100 mutants with pink coloured nodulation to mung bean plant. Out of 100 mutants 10 were promising for nitrogen fixation. The mutant AVR040 showed nitrogenase activity 12.4 μmol/h/mg fresh weight of nodule which is more than wild 9.61μmol/h/mg fresh weight of nodule, while AVR063 showed higher nitrogenase activity 19.4 μmol/h/mg fresh weight of nodule than AVR040.