Effect of physical and chemical mutagens on rhizobium and study of mutated rhizobium activity on seed germination and antibiotic sensitivity

Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria that colonize plant roots and enhance plant growth by a wide variety of mechanisms. Two bacterial isolates were successfully isolated from fresh nodules of groundnut and fenugreek. The isolated Rhizobium strains were allowed for UV irradiation for different time intervals to cause mutation and observed for their consequent action on the growth of groundnut and mung bean. The maximum growth with healthy appearance was resulted in the samples, treated with UV irradiation for 30 min. The isolated strains of rhizobium were also exposed to chemical mutagen (EtBr, Acrylamide and Tetra Methyl Ethylene Diamine - TEMED) to cause mutation and observed for their consequent action on the growth of groundnut and mung bean. When the chemical mutagen, EtBr was treated to groundnuts, there was no growth or sprouting observed in any of the seeds, where as in mung bean all the seeds showed higher growth rates. When the chemical mutagens, Acrylamide and TEMED were treated to groundnuts 50% of the seeds showed sprouting. The same mutagen when treated to mung bean, all the seeds showed higher growth rates. Antibiotic susceptibility and resistance of physically and chemically mutated rhizobium strains were studied tested by four different antibiotics namely, Penicillin-G, Kanamycine, Cefotaxime and Erythromycin. All the mutated strains showed resistance to Pencillin-G.