Isolation and Characterization of some Strains and Mutants of Rhizobium S P. (Vigna) for Poly-â-Hydroxybutyrate (PHB) Production and Symbiotic Properties

Twenty-one wild type (WT) strains of Rhizobium/Bradyrhizobium sp. (Vigna) were screened on minimal medium supplemented with Nile blue A for PHB production by observing yellow/ orange fluorescence under U V. The two WT strains MBR16 and MBR25 were good PHB producers. After their NTG mutagenesis nine mutants producing low, intermediate and high amount of PHB were obtained. Out of all the strains/mutants, the mutant MHt1of MBR16 produced the maximum amount of PHB (1.24 g/l). A highly significant positive correlation was found between the amount of PHB produced by the strains/mutants and shoot dry weight and total shoot nitrogen of mungbean plants inoculated with these strains/mutants.